10.2: The Impact of Nutrition on Hematologic Wellness Across the Lifespan
By the end of this section, you should be able to:
- 10.1.1 Describe the impact of nutrition on the hematologic system during pregnancy.
- 10.1.2 Describe the impact of nutrition on the hematologic system during infancy.
- 10.1.3 Describe the impact of nutrition on the hematologic system during childhood.
- 10.1.4 Describe the impact of nutrition on the hematologic system during adolescence.
- 10.1.5 Describe the impact of nutrition on the hematologic system during adulthood.
- 10.1.6 Describe the impact of nutrition on the hematologic system during later adulthood.
The most common hematologic consequence throughout the lifespan is anemia , affecting approximately 1.8 billion individuals worldwide (Safiri et al., 2021). Although the specific nutrient responsible for nutritional anemia can vary, the condition is characterized by a deficiency in healthy red blood cells . This can lead to various health conditions and is a major public health issue with significant implications for quality of life, productivity, and mortality.
Less common than anemia, nutritional bleeding disorders are a group of conditions that can lead to problems involving prolonged bleeding and thrombosis caused by a lack of nutrients in the diet, such as vitamin K, vitamin C, or iron. Recognizing signs and symptoms related to these deficiencies is critical to avoid life-threatening complications, particularly during health emergencies such as trauma or sepsis. Although seen less frequently, macronutrient and micronutrient deficiencies can also impair immune system function and tissue healing , effects that can be particularly problematic for individuals living with acute or chronic illnesses such as infections or autoimmune diseases.
Controlling anemia requires an interdisciplinary team to prioritize the highest-risk groups, including young children and clients of reproductive age. Despite the nature of the disease, dietary iron deficiency (ID) is the leading cause of anemia in all regions (Safiri et al., 2021). Recent reports indicate an increased trend in anemia and iron deficiency among pregnant clients and young children over the past two decades (National Center for Health Statistics, 2023). According to the World Health Organization (WHO) criteria, anemia and iron deficiency among pregnant individuals and U.S. children have reached the significance of mild and moderate public health problems, respectively (Jefferds et al., 2022). More attention must therefore be paid to nutritional interventions for these high-risk groups.
Impact on Health During Pregnancy
Red blood cell production increases by 30% during pregnancy to support blood volume expansion and fetal growth (Benson et al., 2022). Iron is preferentially used for erythropoiesis (production of red blood cells); therefore, iron deficits can quickly occur, resulting in maternal and fetal anemia.
Anemia affects approximately 36% of pregnant people worldwide and approximately 12% of pregnant people in the United States. The most common causes of anemia in pregnancy are iron deficiency and acute blood loss (Smith et al., 2019; WHO, n.d.-a). Figure 10.2 is an image of human blood from a case of iron deficiency. If iron needs are not met, there is an increased chance of maternal and fetal adverse outcomes. As the severity of anemia worsens, so do the associated risks, which can result in prolonged hospitalization for postpartum clients (Smith et al., 2019; Jefferds et al., 2022). Clients who have multiple births are twice as likely as those who have single births to develop iron deficiency anemia (IDA) due to increased blood volume expansion and utilization of iron stores .
The third trimester of pregnancy is the highest risk period of gestation . If the pregnant client has anemia (any type) during pregnancy, they will have a decreased tolerance of blood loss occurring during birth, increasing their risk for hypovolemic shock , heart failure , infection , and the need for blood transfusion (Sharma et al., 2021; Smith et al., 2019). See Table 10.1 for complications and risks associated with anemia in pregnancy.
Race disparities in nutritional anemia exist both globally and within the United States. According to data from the National Health and Nutrition Examination Survey (NHANES) , a program conducted by the National Center for Health Statistics to assess the health and nutritional status of adults and children in the United States, non-Hispanic Black pregnant women have the highest prevalence of IDA, particularly during the third trimester of pregnancy (Sharma et al., 2021).
| Maternal Risks for Developing Anemia in Pregnancy | Maternal Complications of Anemia | Fetal Complications of Anemia |
|---|---|---|
|
|
|
Screening for anemia and ID in pregnant clients to improve maternal and infant health outcomes is a secondary health promotion intervention. The American College of Obstetricians and Gynecologists (2021) now recommends screening for anemia in all pregnant clients at the first prenatal visit and, if detected, screening for iron deficiency. However, current guidelines do not recommend prepregnancy iron screening. This decreases the chance of early identification because individuals may not be aware they are pregnant until later in the pregnancy.
Iron deficiency and IDA are found equally often among pregnant individuals; however, ID alone doubles in the third trimester and might go completely undetected if the client is asymptomatic (Cochrane et. al, 2022; Nour, 2022). Iron requirements gradually increase during pregnancy from 0.8 mg/day to 7.5 mg/day by the third trimester. The average Western diet includes 1–5 mg of iron daily from food sources; therefore, iron stores will be depleted quickly from a pregnant client if not supplemented (Means, 2020). The Centers for Disease Control and Prevention (CDC) recommends 30 mg/day of elemental iron at the start of pregnancy, and the WHO recommends 60 mg/day. If the pregnant client is diagnosed with anemia during pregnancy, iron should be increased to 60–120 mg/day (National Institutes of Health [NIH], 2023; WHO, n.d.-b).
Elemental iron is a natural substance (heavy metal) directly used by erythrocytes in the body. Nonelemental iron is a chemical compound of iron bound to salt, such as ferrous sulfate. Iron supplements contain an iron salt compound because it is absorbed better than natural iron (Harvard T. H. Chan School of Public Health, 2023). Various iron supplements are available over the counter, which is often confusing for patients and health care professionals. Although health care providers often write prescriptions for iron supplementation, most pharmacies do not carry a “prescription-strength” iron supplement , and clients are directed to over-the-counter products. These product labels will contain two different amounts of iron, elemental and nonelemental; therefore, when providing patient education, nurses must be aware of the amount of elemental iron prescribed and teach clients how to read the labels.
Folate and Vitamin B 12 Requirements
Before the United States FDA began mandating folate fortification in 1998, folate (vitamin B 9 ) deficiency was a common cause of anemia during pregnancy (Ismail et al., 2023). Folate demands increase during pregnancy to support fetal and maternal tissue development (Ballestín et al., 2021). Both anemia and folic acid deficiency can place the fetus at risk for neurologic compromise, including defects in brain development and in the myelination of nerve fibers (Jefferds et al., 2022). Although not a common cause of anemia in most women, vitamin B 12 deficiency can cause serious maternal-fetal consequences for women with gastrointestinal malabsorption.
Folate and vitamin B 12 deficiencies do not always result in macrocytic anemia during pregnancy; however, a physiologic decline is expected (Achebe & Gafter-Gvili, 2017). Folate deficiency in pregnant clients can result in low birth weight and small-for-gestational age (SGA) newborns. Adequate maternal intake of vitamin B 12 is necessary to support fetal growth and development. Signs and symptoms of vitamin B 12 deficiency include fatigue, pallor, tachycardia, poor exercise tolerance, and suboptimal work performance and should be considered in clients with a history of malabsorption conditions (Achebe & Gafter-Gvili, 2017).
As a primary health promotion intervention, the WHO recommends 400 mcg daily of folic acid in pregnant clients until 3 months postpartum. The CDC recommends 400 mcg/day of folic acid for all individuals of childbearing age to prevent neural tube defects in the event of pregnancy. Prenatal vitamins generally contain 1 mg of folate; however, doses of up to 5 mg/day are recommended for those with higher demands, such as during pregnancy in women who have previously had a pregnancy affected by a neural tube defect (Khan, 2023).
Vitamin B 12 is readily stored in excess in the liver , so most pregnant clients are not deficient. However, when vitamin B 12 cannot be obtained or absorbed, such as with dietary insufficiency or malabsorption, hepatic stores are depleted, creating a deficiency (Ankar & Kumar, 2022). This includes pregnant clients with a history of a strict vegan diet for the previous 3 years and those who have undergone bariatric surgery . The WHO and the NIH recommend 2.6 mcg of vitamin B 12 daily during pregnancy, increasing to 2.8 mcg postpartum if breastfeeding (NIH, 2022).
The risk of developing vitamin B 12 deficiency is higher for people who do not get vitamin B 12 from their diet, such as those who are vegetarian or vegan and those with health conditions or medication regimens that interfere with absorption of the vitamin:
- Intestinal diseases
- Previous gastric or ileac resection
- History of celiac disease or inflammatory bowel disease
- Autoimmune disorders ( Graves’ disease , thyroiditis , vitiligo )
- Prolonged use of proton pump inhibitors or H2 receptor antagonists
Clients with a proven deficiency will need higher doses of replacement therapy as follows:
- Deficiency from diet: 1000 mcg orally once daily
- Deficiency from malabsorption: 1000 mcg parenterally (intramuscular injection) once every 3–4 weeks (Ankar & Kumar, 2022)
Infancy
Infancy, from birth to 12 months, is a period of intense physical and developmental growth. Hematopoiesis (formation of blood cellular components) and hemostasis (usual reaction to a bleeding injury to stop blow flow) are incomplete at birth, and micronutrient deficiencies can impair the child’s long-term potential. Requirements for macronutrients and micronutrients are higher during infancy and childhood than other developmental stages and are influenced by the rapid cell division occurring during growth (Physicians Committee for Responsible Medicine, 2020a). Research indicates that micronutrient deficiencies negatively affect the thymus , which can impact lymphocyte function, increasing the risk of infection and inflammatory disease in children (Pai et al., 2018).
Infants receive passive immunity while in utero and through breast milk . This is partially the basis of the American Academy of Pediatrics (AAP) recommendations for breast milk as the “sole source of nutrition for the first 6 months of life, or as long as both mother and baby desire” (Meek et al., 2022). After 6 months, infants should be introduced to supplemental solid foods, including iron-fortified infant cereal. Introducing supplemental foods can be challenging for caregivers, leaving infants and toddlers at additional risk for nutritional deficiencies, especially if food allergies or intolerances are identified. To ensure that infants and young children achieve desirable physical and social milestones, nurses must be well versed in the nutritional considerations affecting this vulnerable population. Educating potential and new parents regarding all health benefits for the breastfed infant is an essential client-centered nursing intervention.
According to the AAP Section on Breastfeeding (Meek et al., 2022), exclusive breastfeeding for the first 6 months of an infant’s life can decrease risk for:
- Acute and chronic infections, including lower respiratory and ear infections and tooth decay
- Food allergies
- Sudden infant death syndrome (SIDS)
- Otitis media
- Eczema
- Asthma
- Childhood and adult obesity
- Types 1 and 2 diabetes
- Gastrointestinal discomfort, including vomiting, diarrhea, and colic
Anemia
According to the WHO, infantile and childhood anemia in the United States ranges from 6–18%, with higher rates among low-income families. As with other age groups, ID is the most common cause of anemia, followed by other nutritional anemias, vitamin B 12 , and folate (NIH, 2022).
Iron deficiency occurs in 12% of infants ages 6–11 months and 8% of toddlers in the United States. Among toddlers, IDA ranges from 0.9–4.4%, depending on the racial and ethnic makeup and socioeconomics of the household (NIH, 2023). During the first 2 years of life, iron needs are high to build iron stores and support the child’s rapid physical and cognitive development rate. Premature infants, infants born to those with iron-deficiency, and infants with low birth weight have been shown to have lifelong learning and memory deficits because of damage to the hippocampus, the brain’s memory center. Accordingly, clinical consequences of ID and IDA in children include (Benson et al., 2022; Drakesmith et al., 2021):
- Impaired psychomotor development and cognitive function
- Delayed attention skills
- Social withdrawal
- Decreased leukocyte and lymphocyte function
- Decreased response to childhood vaccines
- Increased neurotoxicity when ID is associated with high lead blood concentrations
Infant iron stores start to diminish at 6 months of age. After this time, breastfed infants are at greater risk for anemia because the iron content of breast milk depends on the lactating person’s diet, whereas infant formula is fortified with iron. Full-term infants are at the highest risk between ages 6 months and 9 months if they are not consuming iron-fortified formula or successfully introduced to solid foods rich in iron (NIH, 2023). Additionally, children younger than 2 years are more likely than older children to have IDA associated with a transition to solid foods. Recommendations for preventing and treating ID and IDA are shown in Table 10.2.
| Recommending Organization | Infant Considerations | Iron Dosing | Iron-Fortified Foods |
|---|---|---|---|
| Centers for Disease Control and Prevention | Less than 12 months old, not exclusively breastfed | Iron-fortified formula | Label will indicate “with iron” |
| Less than 12 months old, preterm or small for gestational age, exclusively breastfed | 2–4 mg/kg/day elemental iron until 12 months old | ||
| Less than 12 months old, full-term, and appropriate for gestational age, exclusively breastfed |
Consult health care provider for recommendations.
*If eating iron-fortified foods starting at 6 months old, iron supplement may be discontinued. |
|
|
| American Academy of Pediatrics | 4–12 months old, full-term, exclusively breastfed | 1 mg/kg/day elemental iron until eating iron-fortified solid foods | |
| 1–12 months old, preterm, exclusively breastfed | 2 mg/kg/day elemental iron until 12 months old | ||
| World Health Organization | 6–23 months old if diet does not include iron-fortified foods, or if living in a region where anemia prevalence is greater than 40% | 2 mg/kg/day elemental iron until 24 months old |
Individuals living at high altitudes (greater than 1,500 m) are at increased risk for anemia secondary to increased erythropoiesis . This is a compensatory response to a lower oxygen saturation of the blood, so health care professionals must interpret hemoglobin carefully by using altitude-adjusted algorithms (Mairbäurl et al., 2023). Children living at high altitudes may need a greater intake of iron and micronutrients to avoid growth and development delays (Sharma et al., 2019).
Bleeding Risks
Vitamin K is an essential fat-soluble vitamin required for adequate blood clotting. Infants have minimal vitamin K stored at birth because only small amounts pass through the placenta. Vitamin K comes from one of two sources: diet or synthesis by anaerobic (relating to absence of oxygen) bacteria located in the stomach (Yan et al., 2022). A newborn with a healthy gut will not have bacteria-producing vitamin K until approximately 1 week of life. In addition, breast milk contains low quantities of vitamin K. All infants are therefore at high risk for vitamin K deficiency bleeding (VKDB) until they start eating solid foods, which usually occurs at age 4–6 months (Araki & Shirahata, 2020). VKDB is a condition associated with uncontrolled bleeding due to lack of sufficient vitamin K to form blood clots.
To prevent VKDB, the American Academy of Pediatrics (2022) recommends intramuscular (IM) vitamin K prophylaxis as follows:
- Infant birth weight greater than 1500 g: 1 mg vitamin K IM within 6 hours of birth
- Infant birth weight less than 1500 g: 0.3–0.5 mg/kg IM within 6 hours of birth
This risk for VKDB is increased for the following infants:
- Premature infants
- Infants who did not receive vitamin K replacement shortly after birth
- Infants born to mothers with malabsorption or use of antiseizure drugs, antibiotics, warfarin , or antitubercular medications
- Infants with malabsorption, cholestasis (slowing or halt of bile flow from the liver), or liver disease
Table 10.3 outlines the three types of VKDB according to the time of presentation. Early and classic VKDB occur in 1 in 60 to 1 in 250 newborns whereas late VKDB occurs in 1 in 14,000 to 1 in 25,000 infants. Newborns who do not receive a vitamin K injection are 81 times more likely to develop late VKDB (Hand et al., 2022).
| Type | Timing | Associated Factors |
|---|---|---|
| Early | Within 24 hours after birth |
|
| Classic | Within 1 week after birth |
|
| Late | Between 2 weeks and 6 months after birth |
|
Childhood
A variety of nutritional inadequacies exist among school-aged children (aged 5–12 years), ranging from overeating (caloric excess) to undereating, often due to food insecurity. Children who overeat or undereat are at risk for hematologic consequences from nutritional deficiencies. Iron deficiency is the most common micronutrient deficiency in school-aged children, although this age group has the lowest prevalence overall among all children. Anemia in school-aged children is highest among non-Hispanic Black children, and iron deficiency is explicitly highest among Mexican American children. The etiology of deficiency is mostly diet related, apart from children with malabsorption conditions (Jefferds et al., 2022).
Iron plays an essential role in brain metabolism and neurotransmitter function , and deficiencies can lead to cognitive dysfunction (Pivina et al., 2019). School-aged children are undergoing steady linear growth and a high amount of cognitive processing . Iron deficiency with or without anemia can cause decreased school performance due to poor attention span, poor memory, and visual and auditory deficits, compromising “socioemotional development” (Rodríguez-Mañas et al., 2023). Children participating in extracurricular activities may have low energy, negatively impacting their physical performance. Signs and symptoms related to IDA often have a gradual onset in school-aged children and may not be easily detected. Research has shown a positive link between children with attention-deficit hyperactivity disorder (ADHD) and IDA. Therefore, children over 4 years of age demonstrating poor attention or impulsivity should be evaluated for ID (Mattiello et al., 2020). If it is detected, treatment and dietary changes are recommended to ensure intake of 3–6 mg/kg/day of elemental iron for 2–3 months.
Vitamin D Deficiency
Fat-soluble vitamin D is essential for calcium absorption, which takes place in the gastrointestinal tract. It is necessary for optimal bone growth; in addition, vitamin D modulates adaptive immunity, and deficiency is associated with an increased risk of infection (Giannini et al., 2022). The fortification of milk with vitamin D significantly decreased the prevalence of rickets, a softening and weakening of bones that can result in bone deformities. However, with fewer children playing outside and an increase in the use of sunscreen, vitamin D deficiency is once again a public health problem, affecting 15% of children aged 1–11 years (Porto & Abu-Alreesh, 2022). Children at increased risk for vitamin D deficiency include those with:
- Decreased dietary intake of vitamin D
- Dark skin tones
- Excess weight
- Decreased sun exposure
- Malabsorption diseases, including celiac disease , cystic fibrosis , pancreatic insufficiency , and short bowel syndrome
The AAP recommends that all infants younger than 12 months old receive 400 units of supplemental vitamin D daily and that children older than 12 months old receive 600 units daily (Porto & Abu-Alreesh, 2022). Children with risks for deficiency or known deficiency will need higher doses.
Zinc Deficiency
Zinc is a mineral that is essential for growth in children. Deficiencies can impact hematopoiesis, resulting in poor immunity and poor wound healing. Zinc deficiency affects approximately 31% of toddlers 1–3 years old in the United States and up to 80% globally, usually due to poor diet or situations of food insecurity (Vreugdenhil et al., 2021). Zinc is naturally found in meats, poultry, fish, dairy, eggs, and dry legumes, and in the United States, grains and infant cereals are fortified with zinc. Strict vegetarians are at high risk for zinc deficiency because the body does not readily absorb the zinc found in fruits, vegetables, and bread.
Adolescence
Adolescence is the second time in childhood when rapid growth and development occur. Physically, socially, and psychologically, the energy and micronutrient demands are high. However, parental influence on food choices diminishes during this time, often leading to nutritional deficiencies, most commonly iron.
Adolescence is a time of increased iron needs because of the expansion of blood volume and increase in muscle mass. There are sex differences in ID without anemia in adolescents: 9–20% in females but less than 1% in males. The prevalence of IDA in adolescent females who are not menstruating is 3% (Mattiello et al., 2020). Young females are at particular risk for developing iron deficiency because of menstruation . Approximately 7% of menstruating adolescents have IDA, and those who experience menorrhagia (heavy menstrual bleeding) are at increased risk (Eiduson et al., 2021; Mattiello et.al., 2020). It is difficult to quantify heavy menstrual bleeding outside of clinical trials; however, excessive menstrual blood loss that affects quality of life requires further evaluation and treatment (Mansour et al., 2021). Counting how often sanitary pads or tampons are changed can aid in estimating the amount of blood loss; for example, changing sanitary pads or tampons every 1–2 hours is consistent with heavy menstrual bleeding (Fulton, 2022). Common signs and symptoms of ID and IDA in adolescents include:
- Decreased psychomotor skills
- Poor concentration
- Decreased academic performance
- Shortness of breath
- Rapid heart rate
- Headaches
- Dizziness and fainting
- Restless leg syndrome
- Irritability
- Mild weakness
- Fatigue and the need to nap more frequently
Oral iron replacement is recommended as the first step for treating ID and IDA in adolescents, at a dosage of 3–6 mg/kg of elemental iron daily for 2–3 months (Miniero et al., 2019). Adolescents will also need counseling regarding dietary modifications and ways to manage potential adverse effects of iron replacement. Long-term dietary changes will be necessary for female adolescents with ID or IDA associated with menstruation. For therapy to be successful, dietary modifications should reflect individual preferences. Vegetarian options may include legumes, beans, tofu, rolled oats, and quinoa.
Read the following clinical scenario and then answer the questions that follow. This case study will evolve throughout the chapter.
The nurse prepares to assess Catalina for more details about her past medical history and current health concerns. Catalina reports that prior to the past few months, she had felt great and had managed her grades and social life well. She does not take any medications regularly, including daily vitamins. Her mother confirms that she has no significant past medical issues, which makes her current symptoms more concerning. Catalina never complains and has always prioritized her grades. Catalina and her mother confirm that nothing has changed in their social circumstances, and Catalina denies symptoms of depression.
The nurse is aware that adolescent females are at risk for anemia and ID once menstruation begins and therefore takes a detailed menstrual bleeding history. Catalina reports that she has had regular menstrual cycles lasting 5–7 days since age 13 years but has noticed an increase in the heaviness of her flow this school year. She further says that her use of sanitary pads has increased, and she must change her pad every 1–2 hours during the day and night. The nurse recognizes this as a sign of heavy menstrual bleeding and notifies the health care provider of her concern that Catalina may be anemic and iron deficient.
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6 mg/kg/dose twice daily for 3 months
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3–6 mg/kg/day for 6 months
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3 mg/kg/day until anemia is resolved
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Ask her to identify her food likes and dislikes.
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List the foods she must eat each week.
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Explain that she needs to make these changes on just a short-term basis until her anemia resolves.
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Explain that the iron supplement has side effects that she will have to tolerate if she is prescribed that medication.
Adolescent athletes face unique challenges related to nutritional needs. They are already at risk for nutritional deficiencies because of rapid growth, unhealthy food choices, and high-risk behaviors. Adolescent athletes have a high nutritional demand due to the daily energy expenditure associated with training and having less time to make healthy food choices. Additionally, many athletes strive for a lean body composition for a competitive edge, setting them up for disordered eating patterns that can have lifelong effects on their overall health (Kontele & Vassilakou, 2021). Adolescent athletes who limit their intake of meat products are at even higher risk for iron imbalance. Because of increased iron needs combined with potentially low iron intake and increased blood loss from menstruation, ID and IDA are common problems among adolescent female athletes and can affect their physical endurance and cognitive performance. In males, ID is often associated with higher physiologic needs from excessive training rather than from diet alone (Desbrow, 2021).
Iron deficiency can manifest as extreme fatigue, increased susceptibility to infection, impaired skeletal muscle function, and poor decision-making (Berg, 2019). Assessment for ID and IDA should be considered for both male and female athletes demonstrating these symptoms. Athletes at the highest risk for iron deficiency include those who are female; are underweight or undernourished; are vegetarian or consume limited amounts of iron-rich foods; have underlying malabsorption conditions; or compete in endurance sports.
Adulthood
As in other age groups, ID and IDA remain the highest cause of anemia in young and middle adults, although other nutrient deficiencies such as folate and vitamin B 12 contribute (NIH, 2023). In adults ages 19–50, males require more zinc and vitamins C, K, and B complex, and menstruating females of the same age require more iron. Females are twice as likely as males to have nutritional anemia, and moderate to severe anemia is five times more common in nonpregnant females than in males. Race differences are prevalent, with the highest incidence in non-Hispanic Black adults, followed by Hispanic and White individuals (Malek et.al, 2019; Physicians Committee for Responsible Medicine, 2020a; Rodríguez-Mañas et al., 2023).
Modern health care relies on healthy adults to maintain the blood supply. However, 25–35% of frequent blood donors will develop ID, which may not be detected if it is present without anemia (NIH, 2023). This raises concern for the frequent blood donor’s health and the quality of blood they donate (Hod et al., 2022).
Folic acid, vitamin B 12 , and vitamin K deficiencies in adults can also be secondary to chronic liver disease and excessive alcohol intake. Middle adults in the United States consume less than the recommended daily requirements for most essential micronutrients, leading to deficiencies that increase the risk for certain chronic conditions. Chronic diseases are now increasingly common among young adults, often because of poor nutrition, lack of physical activity, and smoking (Rodríguez-Mañas et al., 2023). Sixty percent of adults with chronic heart failure have ID, and 17% of those have IDA. The etiology of this is multifactorial and may be related to:
- Poor nutrition
- Malabsorption
- Defective mobilization of iron stores
- Cardiac cachexia (unintentional severe weight loss caused by heart failure)
- Use of aspirin or other anticoagulant medications that can lead to microscopic blood loss in the gastrointestinal tract
The economic burden on adults with IDA includes reduced physical productivity and work capacity due to associated symptoms such as fatigue, weakness, and shortness of breath (Jefferds et al., 2022).
Later Adulthood
Aging naturally impacts physical changes, even in the healthiest adults, but healthy aging depends on proper nutrition (Kaur et al., 2019). Although energy needs decrease with age, specific micronutrient needs increase. As they age, adults become susceptible to nutrient-deficient blood abnormalities secondary to a decreased production of hormones and red blood cells, as well as decreased appetite and food intake related to delayed gastric emptying and declining oral health . In addition, older clients may experience nutritional challenges due to age- or disease-related conditions associated with chewing, swallowing, digestion, and absorption of nutrients (Physicians Committee for Responsible Medicine, 2020a). Malnutrition in this phase of life can result in lower physical function, poor quality of life, a greater risk for loss of muscle mass, and a shorter lifespan (Kaur et al., 2019; Rodríguez-Mañas et al., 2023).
Zinc deficiency occurs in approximately 60% of adults older than 70 years, leading to an increased risk for infection. Decreased dietary zinc intake and the physiologic decline in gastrointestinal absorption are the most likely reasons for this deficiency (Kaur et al., 2019).
Iron Deficiency
Older adults have the greatest incidence of nutritional anemia overall, with those aged 80–85 years having the highest. This is the only age group in which males have a greater incidence of anemia than females—as much as two times more. Older adults with anemia have increased hospitalization rates and mortality. Approximately 25–30% of older adults with congestive heart failure have anemia, worsening functional capacity, and are at increased risk of death (Ambrosy et al., 2019). With advancing age, iron stores diminish. This, along with decreased dietary intake of iron-rich foods and increased incidence of gastrointestinal malabsorption and occult blood loss, contributes to ID and IDA in older adults (Burton et al., 2020; Kaur et al., 2019). The prevalence of IDA in older adults is detailed in Table 10.4.
| Age | Male | Female |
|---|---|---|
| 65–75 years | 11% | 10.2% |
| 76–85 years | 15% | 7–12% |
| Older than 85 years | 30% | 17% |
Signs and symptoms of IDA in older adults may include:
- Depression
- Fatigue
- Loss of muscle strength
- Decreased cognitive function
Iron-rich foods, such as fortified grains and cereals, and oral replacement are the first step once a deficiency is confirmed; however, parenteral iron replacement may be required due to the frequency of gastrointestinal malabsorption in this population (Burton et al., 2020).
Folate and Vitamin B Deficiencies
Vitamin B 12 and folate deficiencies among older adults remain a significant challenge. Approximately 10–30% of older adults are affected by atrophic gastritis, which can interfere with the absorption of vitamin B 12 and folate (NIH, 2022). Additionally, the metabolic processes of each micronutrient are interconnected, so it is difficult to distinguish the source of physical manifestations (Socha et al., 2020). Signs and symptoms include:
- Risk for cardiovascular disease
- Cognitive impairment
- Insomnia
- Impaired mood
- Decreased decision-making ability
- Decreased physical performance, leading to increased risk for falls and fractures
Folate deficiency is more likely to be related to decreased absorption and reduced dietary intake, whereas vitamin B 12 deficiency is more often associated with diseases of malabsorption and polypharmacy . Mild vitamin B 12 deficiency occurs in 20% of adults older than 60, and severe deficiency occurs in 6% of adults older than 70 (NIH, 2022). Nonhematologic symptoms range from vague and nonspecific to severe neurologic and neuropsychiatric disorders (Stauder et al., 2018). Folate deficiency is reported to occur in 5–20% of older adults and is more common in those who smoke, consume excessive amounts of alcohol, are obese, or live alone (Rotstein et al., 2022). Vitamin B 12 deficiency anemia is more likely to be associated with neurologic symptoms not seen in individuals with folate deficiency anemia (Stauder et al., 2018). Anemia associated with both of these deficiencies can be distinguished from IDA based on the size of red blood cells; iron deficiency anemia is microcytic, whereas folate and vitamin B 12 deficiencies are macrocytic. Treatment is focused on nutrient replacement and diet modification.


4.8: Terminology Associated with Equations
Independent and Dependent Variables
Independent and Dependent Variables
In an equation, any variable whose value can be freely assigned is said to be an independent variable. Any variable whose value is determined once the other values have been assigned is said to be a dependent variable. Two examples will help illustrate these concepts.
- Consider the equation \(y=2x−7\). If we are free to choose values for \(x\), then \(x\) would be considered the independent variable. Since the value of \(y\) depends on the value of \(x, y\) would be the dependent variable.
- Consider the equation \(m=−4gk^2\). If we are free to choose values for both \(g\) and \(k\), then g and k would be considered independent variables. Since the value of m depends on the values chosen for g and k, m would be the dependent variable.
The Domain of an Equation
Domain
The process of replacing letters with numbers is called numerical evaluation. The collection of numbers that can replace the independent variable in an equation and yield a meaningful result is called the domain of the equation. The domain of an equation may be the entire collection of real numbers or may be restricted to some subcollection of the real numbers. The restrictions may be due to particular applications of the equation or to problems of computability.
Sample Set A
Find the domain of each of the following equations.
\(y = \dfrac{2}{x}\), where \(x\) is the independent variable.
Any number except 0 can be substituted for \(x\) and yield a meaningful result. Hence, the domain is the collection of all real numbers except 0.
\(d = 55t\), where \(t\) is the independent variable and the equation relates time, \(t\), and distance \(d\).
It makes little sense to replace \(t\) by a negative number, so the domain is the collection of all real numbers greater than or equal to 0.
\(k = \dfrac{2w}{w-4}\), where the independent variable is \(w\).
The letter \(w\) can be replaced by any real number except 4 since that will produce a division by 0. Hence, the domain is the collection of all real numbers except 4.
\(a = 5b^2 + 2b - 6\), where the independent variable is \(b\).
We can replace \(b\) by any real number and the expression \(5b^2 + 2b - 6\) is computable. Hence, the domain is the collection of all real numbers.
Practice Set A
Find the domain of each of the following equations. Assume that the independent variable is the variable that appears in the expression on the right side of the "=" sign.
\(y = 5x + 10\)
- Answer
-
All real numbers
\(y = \dfrac{5}{x}\)
- Answer
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all real numbers except 0
\(y = \dfrac{3+x}{x}\)
- Answer
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All real numbers except 0
\(y = \dfrac{9}{x-6}\)
- Answer
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All real numbers except 6
\(m = \dfrac{1}{n+2}\)
- Answer
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All real numbers except \(-2\).
\(s = \dfrac{4}{9}t^2\), where this equation relates the distance an object falls, \(s\), to the time, \(t\), it has had to fall.
- Answer
-
All real numbers greater than or equal to 0
\(g = \dfrac{4h-7}{21}\)
- Answer
-
All real numbers
Exercises
For the following problems, find the domain of the equations. Assume that the independent variable is the variable that appears in the expression to the right of the equal sign.
\(y = 4x + 7\)
- Answer
-
\(x\) = all real numbers
\(y = 3x - 5\)
\(y = x^2 + 2x - 9\)
- Answer
-
\(x\) = all real numbers
\(y = 8x^3 - 6\)
\(y = 11x\)
- Answer
-
\(x\) = all real numbers
\(s = 7t\)
\(y = \dfrac{3}{x}\)
- Answer
-
\(x\) = all real numbres except zero
\(y = \dfrac{2}{x}\)
\(m = \dfrac{-16}{h}\)
- Answer
-
\(h\) = all real numbers except zero
\(k = \dfrac{4t^2}{t-1}\)
\(t = \dfrac{5}{s-6}\)
- Answer
-
\(s\) = all real numbers except 6
\(y = \dfrac{12}{x+7}\)
Exercises for Review
Name the property of real numbers that makes \(4yx^2 = 4x^2y\) a true statement.
- Answer
-
commutative property of multiplication
Simplify \(\dfrac{x^{5n+6}}{x^4}\)
Supply the missing phrase. Absolute value speaks to the question of and not "which way."
- Answer
-
"how far"
Find the product. \((x-8)^2\).
Find the product. \((4x+3)(4x-3)\).
- Answer
-
\(16x^2 - 9\)


3.3.3: Glaciers
While ice sheets and sea ice are restricted to the poles, glaciers occur throughout the world, even in tropical locations, where mountain ranges reach elevations high enough to allow the development of ice. For example, both New Zealand and Chile contain high-elevation mountain glaciers. The World Glacier Monitoring Service (WGMS) tracks and reports data on ‘reference’ glaciers (glaciers with greater than 30 years of documented mass-balance measurements). Mass data on these reference glaciers indicates significant degrees of glacier mass loss across the globe (Fig <IP_ADDRESS>).
In 1997, researchers at the Northern Rocky Mountain Science Center began the Repeat Photography Project to illustrate changes in glacier extent in Glacier National Park , Montana, USA through current and historical photography. The value of this project is illustrated by the highly visible change in Grinnell Glacier from 1938 to 2015 (Fig <IP_ADDRESS>). Warming and glacier melt is so severe in this region that a 2003 study estimated that the park may be ice-free, containing not a single glacier, by the year 2030 ( Hall and Fagre, 2003 ), though other studies have predicted some glaciers may persist as long as 2080 ( Brown et al 2010 ).
Image Credits
- WGMS (2020, updated, and earlier reports). Global Glacier Change Bulletin No. 3 (2016-2017). Zemp, M., Gärtner-Roer, I., Nussbaumer, S. U., Bannwart, J., Rastner, P., Paul, F., and Hoelzle, M. (eds.), ISC(WDS)/IUGG(IACS)/UNEP/UNESCO/WMO, World Glacier Monitoring Service, Zurich, Switzerland, 274 pp., publication based on database version: doi:10.5904/wgms-fog-2019-12 .
- https://www.usgs.gov/centers/norock/science/grinnell-glacier-mount-gould?qt-science_center_objects=0#qt-science_center_objects


4.8: Popular Culture: Prisoner's Dilemma and Chicken
In this section, we will look at applications of Prisoner's Dilemma and Chicken in popular culture.
The movie Return to Paradise (\(1998\)) explores a Prisoner's Dilemma throughout the film. The two main characters, Tony and Sheriff, must decide if they will cooperate by returning to Malaysia to serve time in prison, or defect by not returning to Malaysia.  If both cooperate, their friend will be released and they will each serve short sentences.
Give a payoff matrix to model the Prisoner's Dilemma in the film. By the end of the film have the payoffs changed? Is it still a Prisoner's Dilemma? Explain.
In the classic Prisoner's Dilemma, communication is not allowed between the players. In the film, Tony and Sheriff can communicate all they want. How does this communication impact the Prisoner's Dilemma. Does it help or hinder their choice of strategy? Explain.
The movie Rebel Without a Cause (\(1955\)) contains an iconic Chicken scene, in which the two characters race towards a cliff. The last one to jump out of his car is declared the winner.
Does Jim win or lose the game of Chicken? Explain your answer.
The movie Footloose (\(1984\)) also has a Chicken scene (this time with tractors). Compare the Chicken scenes in Rebel and Footloose . Is the Chicken game used similarly in each? In both scenes, one player has no choice of strategy. Why might the writer have made this choice in each of these films?
Now try to apply the ideas of rationality and perfect information to your own popular culture examples.
Suppose players are allowed to communicate in a Prisoner's Dilemma. Explain the relationship between trust and communication in a Prisoner's Dilemma. Give an example from a film demonstrating the relationship.
Why might a writer include a Chicken scene in a film? What key attributes might the director be trying to display about the winner of Chicken and the loser? Use an example from popular culture to demonstrate your answer.
One of the interesting comparisons between Prisoner's Dilemma ad Chicken is that in a Prisoner's Dilemma is with their equilibrium points. Players in a Prisoner's Dilemma can reach an equilibrium point if they play the same way. Players in a Chicken game can reach an equilibrium if they choose different strategies. Find examples of how these games are used in popular culture to emphasize differences between characters.


3.8: Bibliography
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Benjamin-Fink, N., and B.K. Reilly. 2017. Conservation implications of wildlife translocations: The state’s ability to act as conservation units for wildebeest populations in South Africa. Global Ecology and Conservation 12: 46–58. https://doi.org/10.1016/j.gecco.2017.08.008
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Brown, D.M., R.A. Brenneman, K.P. Koepfli, et al. 2007. Extensive population genetic structure in the giraffe. BCM Biology 5: 57. https://doi.org/10.1186/1741-7007-5-57
CBD (Center for Biological Diversity). 2015. Petition to reclassify and uplist African elephants from Threatened to Endangered under the Endangered Species Act as two separate species: forest elephants (Loxodonta cyclotis) and savannah elephants (Loxodonta africana) (Tucson: CBD). https://www.biologicaldiversity.org/species/mammals/pdfs/African_Elephant_Uplisting_Petition.pdf
Ceballos, G., and P.R. Ehrlich. 2009. Discoveries of new mammal species and their implications for conservation and ecosystem services. Proceedings of the National Academy of Sciences 106: 3841–46. https://doi.org/10.1073/pnas.0812419106
Coetzer, W.R., C.T. Downs, M.R. Perrin, et al. 2015. Molecular systematics of the Cape Parrot (Poicephalus robustus): Implications for taxonomy and conservation. PLoS ONE 10: e0133376. https://doi.org/10.1371/journal.pone.0133376
Collinson, J.M., M. Päckert, Y. Lawrie, et al. 2018. Taxonomic status of the Liberian Greenbul Phyllastrephus leucolepis and the conservation importance of the Cavalla Forest, Liberia. Journal of Ornithology 159: 19–27. https://doi.org/10.1007/s10336-017-1477-0
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Corlett, R., and R.B. Primack. 2010. Tropical Rainforests: An Ecological and Biogeographical Comparison (Malden: Wiley-Blackwell). https://doi.org/10.1002/9781444392296
Costello, M.J., S. Wilson, and B. Houlding. 2012. Predicting total global species richness using rates of species description and estimates of taxonomic effort. Systematic Biology 61: 871–83. http://doi.org/10.1093/sysbio/syr080
Davis A.P., T.W. Gole, S. Baena, et al. 2012. The impact of climate change on indigenous Arabica coffee (Coffea arabica): Predicting future trends and identifying priorities. PLoS ONE 7: e47981. http://doi.org/10.1371/journal.pone.0047981
de Jong, Y.A., and T.M. Butynski. 2010. Three sykes’s monkey Cercopithecus mitis × vervet monkey Chlorocebus pygerythrus hybrids in Kenya. Primate Conservation 25: 43–56. https://doi.org/10.1896/052.025.0109
Dijkstra, K.-D.B., J. Kipping, and M. Nicolas. 2015. Sixty new dragonfly and damselfly species from Africa (Odonata). Odonatologica 44: 447–678.
Downs, C.T., M. Pfeiffer, and L. Hart. 2014. Fifteen years of annual Cape Parrots (Poicephalus robustus) censuses: Current population trends and conservation contributions. Ostrich 85: 273–80. https://doi.org/10.2989/00306525.2014.959088
Ebert, D.A., and G.M. Cailliet. 2011. Pristiophorus nancyae, a new species of sawshark (Chondrichthyes: Pristiophoridae) from southern Africa. Bulletin of Marine Science 87: 501–12. https://doi.org/10.5343/bms.2010.1108
Evans B.J., T.F. Carter, E. Greenbaum, et al. 2015. Genetics, morphology, advertisement calls, and historical records distinguish six new polyploid species of African clawed frog (Xenopus, Pipidae) from West and Central Africa. PLoS ONE 10: e0142823. https://doi.org/10.1371/journal.pone.0142823
Fennessy, J., T. Bidon, F. Reuss, et al. 2016. Multi-locus analysis reveals four giraffe species instead of one. Current Biology 26: 2543–49. https://doi.org/10.1016/j.cub.2016.07.036
Gerlach, J. 2009. Pachnodus velutinus. The IUCN Red List of Threatened Species 2009: e.T40091A10304648. http://doi.org/10.2305/IUCN.UK.2009-2.RLTS.T40091A10304648.en
Goodwin, Z.A., D.J. Harris, D. Filer, et al. 2015. Widespread mistaken identity in tropical plant collections. Current Biology 25: R1066–R1067. https://doi.org/10.1016/j.cub.2015.10.002
Grobler, J.P., I. Rushworth, J.S. Brink, et al. 2011. Management of hybridization in an endemic species: decision making in the face of imperfect information in the case of the black wildebeest—Connochaetes gnou. European Journal of Wildlife Research 57: 997–1006. http://doi.org/10.1007/s10344-011-0567-1
Groves, C.P., F.P.D. Cotterill, S. Gippoliti, et al. 2017. Species definitions and conservation: A review and case studies from African mammals. Conservation Genetics 18: 1247–`156. https://doi.org/10.1007/s10592-017-0976-0
Hart, J.A., K.M. Detwiler, C.C. Gilbert, et al. 2012. Lesula: A new species of Cercopithecus monkey endemic to the Democratic Republic of Congo and implications for conservation of Congo’s Central Basin. PLoS ONE 7: e44271. http://doi.org/10.1371/journal.pone.0044271
IUCN, 2019. The IUCN Red List of Threatened Species. http://www.iucnredlist.org
Jackson, C.R., and M.P. Robertson. 2011. Predicting the potential distribution of an endangered cryptic subterranean mammal from few occurrence records. Journal for Nature Conservation 19: 87–94. http://doi.org/10.1016/j.jnc.2010.06.006
Larsen, B.B., E.C. Miller, M.K. Rhodes, et al. 2017. Inordinate fondness multiplied and redistributed: The number of species on Earth and the new pie of life. Quarterly Review of Biology 92: 229–65. https://doi.org/10.1086/693564
Maree S., N.C. Bennett, and G.N. Bronner. 2016. A conservation assessment of Neamblysomus julianae. In: The Red List of Mammals of South Africa, Swaziland and Lesotho, ed. by M.F. Child, et al. (Cape Town and Johannesburg: SANBI and EWT).
Maree S. 2017. Planning for persistence of a Juliana’s Golden Mole (Neamblysomus julliane) subpopulation threatened by urban development on the Bronberg Ridge of Pretoria (Tshwane), South Africa. IUCN/SSC Afrotheria Specialist Group Newsletter 13: 24–33. https://www.afrotheria.net/newsletter.php
Maree, S. 2015. Neamblysomus julianae. The IUCN Red List of Threatened Species 2015: e.T1089A21285354. http://doi.org/10.2305/IUCN.UK.2015-2.RLTS.T1089A21285354.en
Marnewick, M.D., E.R. Retief, N.T. Theron, et al. 2015. Important Bird and Biodiversity Areas of South Africa (Johannesburg: BirdLife South Africa). https://www.birdlife.org.za/images/IBA/Documents/IBA%20Version%202.pdf
Minhós, T., E. Wallace, M.J.F. da Silva, et al. 2013. DNA identification of primate bushmeat from urban markets in Guinea-Bissau and its implications for conservation. Biological Conservation 167: 43–49. https://doi.org/10.1016/j.biocon.2013.07.018
Mondol, S., I. Moltke, J. Hart, et al. 2015. New evidence for hybrid zones of forest and savanna elephants in Central and West Africa. Molecular Ecology 24: 6134–47. https://doi.org/10.1111/mec.13472
Musick, J.A. 2000. Latimeria chalumnae. The IUCN Red List of Threatened Species 2000: e.T11375A3274618. http://doi.org/10.2305/IUCN.UK.2000.RLTS.T11375A3274618.en
Mynhardt, S., S. Maree, I. Pelser, Net al. 2015. Phylogeography of a morphologically cryptic golden mole assemblage from South-Eastern Africa. PLoS ONE 10: e0144995. https://doi.org/10.1371/journal.pone.0144995
Nichols, E., T.A. Gardner, C.A. Peres, et al. 2009. Co‐declining mammals and dung beetles: An impending ecological cascade. Oikos 118: 481–87. https://doi.org/10.1111/j.1600-0706.2009.17268.x
Parker, J., A.J. Helmstetter, D. Devey, et al. 2017. Field-based species identification of closely-related plants using real-time nanopore sequencing. Scientific Reports 7: 8345. https://doi.org/10.1038/s41598-017-08461-5
Pennisi, E. 2016. Pocket DNA sequencers make real-time diagnostics a reality. Science 351: 800–01. https://doi.org/10.1126/science.351.6275.800
Plumptre, A.J., and T. Wronski. 2013. Tragelaphus scriptus Bushbuck. In: Mammals of Africa: v. VI: Pigs, Hippopotamuses, Chevrotain, Giraffes, Deer and Bovids, ed. by J. Kingdon and M. Hoffmann (London: Bloomsbury Publishing).
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Ruggiero, M.A., D.P. Gordon, T.M. Orrell, et al. 2015. A higher-level classification of all living organisms. PLoS ONE 10: e0119248. http://doi.org/10.1371/journal.pone.0119248
Salzburger, W., S. Baric, and C. Sturmbauer. 2002. Speciation via introgressive hybridization in East African cichlids? Molecular Ecology 11: 619–25. http://doi.org/10.1046/j.0962-1083.2001.01438.x
Shirley, M.H., A.N. Carr, J.H. Nestler, et al. 2018. Systematic revision of the living African slender-snouted crocodiles (Mecistops Gray, 1844). Zootaxa 4504: 151–93. http://doi.org/10.11646/zootaxa.4504.2.1
Takahara, T., T. Minamoto, and H. Doi. 2013. Using environmental DNA to estimate the distribution of an invasive fish species in ponds. PLoS ONE 8: e56584. https://doi.org/10.1371/journal.pone.0056584
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1.6: Respiratory Protection
The information in this section will provide basic information to workers and employers who may find themselves using respiratory protection for the first time. The guidance provides information on what respirators are, how they work, and what is needed for a respirator to provide protection. For additional information see OSHA Bulletin: General Respiratory Protection Guidance for Employers and Workers
What is a respirator?
A respirator is a device that protects you from inhaling dangerous substances, such as chemicals and infectious particles. Respirators are among the most important pieces of protective equipment for working in hazardous environments. Selecting the right respirator requires an assessment of all the workplace operations, processes or environments that may create a respiratory hazard. The identity of the hazard and its airborne concentrations need to be determined before choosing a respirator. This assessment should be done by experienced safety personnel or by an industrial hygienist. There are several different types of respirators, as described below.
How do respirators work?
Respirators work by either filtering particles from the air, chemically cleaning (purifying) the air, or supplying clean air from an outside source.
Particulate Respirators
Particulate respirators are the simplest, least expensive, and least protective of the respirator types available. These respirators only protect against particles (e.g., dust). They do not protect against chemicals, gases, or vapors, and are intended only for low hazard levels. The commonly known “N-95” filtering facepiece respirator or “dust mask” is one type of particulate respirator, often used in hospitals to protect against infectious agents. Particulate respirators are “airpurifying respirators” because they clean particles out of the air as you breathe.
Particulate respirators:
- Filter out dusts, fumes and mists.
- Are usually disposable dust masks or respirators with disposable filters.
- Must be replaced when they become discolored, damaged, or clogged.
Examples: filtering facepiece or elastomeric respirator.
Chemical Cartridge/Gas Mask Respirator
Gas masks are also known as “air-purifying respirators” because they filter or clean chemical gases out of the air as you breathe. This respirator includes a facepiece or mask, and a cartridge or canister. Straps secure the facepiece to the head. The cartridge may also have a filter to remove particles.
Gas masks are effective only if used with the correct replaceable cartridge or filter (these terms are often used interchangeably) for a particular biological or chemical substance. Selecting the proper filter can be a complicated process, but is aided through color-coding based on the substance being filtered. There are cartridges available that protect against more than one hazard, but there is no “all-in-one” cartridge that protects against all substances. You may even require more than one cartridge to protect against multiple hazards. It is important to know what hazards you will face in order to be certain you are choosing the right filters/cartridges.
There are nine classes of particulate filters which are broken down into three series: N, R, and P. Each series (N, R, and P) is available at three efficiency levels: 95%, 99%, and 99.97%. The N series filter is used in environments free of oil mists. The R series filters can be exposed to oil mists, but should only be worn for one work shift. The P filter can be exposed to oil mists for longer than one work shift.
| Contaminant | Color | Description |
|---|---|---|
| Acid gases | White | |
| Hydrocyanic acid gas | White with 1/2 inch green stripe completely around the canister near the bottom | |
| Chlorine gas | White with 1/2 inch yellow stripe completely around the canister near the bottom | |
| Organic Vapors | Black | |
| Ammonia gas | Green | |
| Acid gases and ammonia gas | Green with 1/2 inch white stripe completely around the canister near the bottom | |
| Carbon monoxide | Blue | |
| Acid gases & organic vapors | Yellow | |
| Hydrocyanic acid gas and chloropicrin vapor | Yellow with 1/2 inch blue stripe completely around the canister near the bottom | |
| Acid gases, organic vapors, and ammonia gases | Brown | |
| Radioactive materials, except tritium & noble gases | Magenta | |
| Pesticides | Organic vapor canister plus a particulate filter | |
| Multi-Contaminant and CBRN agent | Olive | |
| Any particulates - P100 | Purple | |
| Any particulates - P95, P99, R95, R99, R100 | Orange | |
| Any particulates free of oil - N95, N99, or N100 | Teal |
Powered Air-Purifying Respirator (PAPR)
Powered air-purifying respirators use a fan to draw air through the filter to the user. They are easier to breathe through; however, they need a fully charged battery to work properly. They use the same type of filters/cartridges as other air-purifying respirators. It is important to know what the hazard is, and how much of it is in the air, in order to select the proper filters/cartridges.
Self-Contained Breathing Apparatus
Self-Contained Breathing Apparatus (SCBA) is the respirator commonly used by firefighters. These use their own air tank to supply clean air, so you don’t need to worry about filters. They also protect against higher concentrations of dangerous chemicals. However, they are very heavy (30 pounds or more), and require very special training on how to use and to maintain them. Also, the air tanks typically last an hour or less depending upon their rating and your breathing rate (how hard you are breathing).
Provide clean air from a portable air tank when the air around you is simply too dangerous to breathe.
All of these respirators (except for the “dust masks” or filtering face pieces) are available in either half-mask or full-face pieces.
Frequently Asked Questions (Respirators)
Query \(\PageIndex{1}\)
Respirator Considerations:
Questions to consider regarding any respirator you are considering purchasing:
- What protection (which chemicals and particles, and at what levels) does the respirator provide?
- Is there more than one size?
- Which size should I use?
- How do I know if the gas mask or respirator will fit?
- What type of training do I need?
- Are there any special maintenance or storage conditions?
- Will I be able to talk while wearing the respirator?
- Does the hood restrict vision or head movement in any way?
- Can I carry the device in the trunk of my automobile?
- Is a training respirator available?
Additional Information
For more information on OSHA’s rules and requirements related to respiratory protection, visit OSHA’s website at www.osha.gov/SLTC/respiratoryprotection/index.html.
This is one in a series of informational fact sheets highlighting OSHA programs, policies or standards. It does not impose any new compliance requirements. For a comprehensive list of compliance requirements of OSHA standards or regulation, refer to Title 29 of the Code of Federal Regulations. This information will be made available to sensory-impaired individuals upon request. The voice phone is<PHONE_NUMBER>; teletypewriter (TTY) number:<PHONE_NUMBER>.
For more complete information:
OSHA
Occupational Safety and Health Administration
U.S. Department of Labor
www.osha.gov
(800) 321-OSHA


11.6: Colloids
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Learning Objectives
By the end of this section, you will be able to:
- Describe the composition and properties of colloidal dispersions
- List and explain several technological applications of colloids
As a child, you may have made suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water, known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles that are visible (or that can be seen with a magnifying glass). They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved species are molecules or ions. Solutions exhibit completely different behavior from suspensions. A solution may be colored, but it is transparent, the molecules or ions are invisible, and they do not settle out on standing. Another class of mixtures called colloids (or colloidal dispersions ) exhibit properties intermediate between those of suspensions and solutions (Figure \(\PageIndex{1}\)). The particles in a colloid are larger than most simple molecules; however, colloidal particles are small enough that they do not settle out upon standing.
The particles in a colloid are large enough to scatter light, a phenomenon called the Tyndall effect . This can make colloidal mixtures appear cloudy or opaque, such as the searchlight beams shown in Figure \(\PageIndex{2}\). Clouds are colloidal mixtures. They are composed of water droplets that are much larger than molecules, but that are small enough that they do not settle out.
The term “colloid”—from the Greek words kolla , meaning “glue,” and eidos , meaning “like”—was first used in 1861 by Thomas Graham to classify mixtures such as starch in water and gelatin. Many colloidal particles are aggregates of hundreds or thousands of molecules, but others (such as proteins and polymer molecules) consist of a single extremely large molecule. The protein and synthetic polymer molecules that form colloids may have molecular masses ranging from a few thousand to many million atomic mass units.
Analogous to the identification of solution components as “solute” and “solvent,” the components of a colloid are likewise classified according to their relative amounts. The particulate component typically present in a relatively minor amount is called the dispersed phase and the substance or solution throughout which the particulate is dispersed is called the dispersion medium . Colloids may involve virtually any combination of physical states (gas in liquid, liquid in solid, solid in gas, etc.), as illustrated by the examples of colloidal systems given in Table \(\PageIndex{1}\).
| Dispersed Phase | Dispersion Medium | Common Examples | Name |
|---|---|---|---|
| solid | gas | smoke, dust | — |
| solid | liquid | starch in water, some inks, paints, milk of magnesia | sol |
| solid | solid | some colored gems, some alloys | — |
| liquid | gas | clouds, fogs, mists, sprays | aerosol |
| liquid | liquid | milk, mayonnaise, butter | emulsion |
| liquid | solid | jellies, gels, pearl, opal (H 2 O in SiO 2 ) | gel |
| gas | liquid | foams, whipped cream, beaten egg whites | foam |
| gas | solid | pumice, floating soaps | — |
Preparation of Colloidal Systems
Colloids are prepared by producing particles of colloidal dimensions and distributing these particles throughout a dispersion medium. Particles of colloidal size are formed by two methods:
- Dispersion methods: breaking down larger particles. For example, paint pigments are produced by dispersing large particles by grinding in special mills.
- Condensation methods: growth from smaller units, such as molecules or ions. For example, clouds form when water molecules condense and form very small droplets.
A few solid substances, when brought into contact with water, disperse spontaneously and form colloidal systems. Gelatin, glue, starch, and dehydrated milk powder behave in this manner. The particles are already of colloidal size; the water simply disperses them. Powdered milk particles of colloidal size are produced by dehydrating milk spray. Some atomizers produce colloidal dispersions of a liquid in air.
An emulsion may be prepared by shaking together or blending two immiscible liquids. This breaks one liquid into droplets of colloidal size, which then disperse throughout the other liquid. Oil spills in the ocean may be difficult to clean up, partly because wave action can cause the oil and water to form an emulsion. In many emulsions, however, the dispersed phase tends to coalesce, form large drops, and separate. Therefore, emulsions are usually stabilized by an emulsifying agent , a substance that inhibits the coalescence of the dispersed liquid. For example, a little soap will stabilize an emulsion of kerosene in water. Milk is an emulsion of butterfat in water, with the protein casein serving as the emulsifying agent. Mayonnaise is an emulsion of oil in vinegar, with egg yolk components as the emulsifying agents.
Condensation methods form colloidal particles by aggregation of molecules or ions. If the particles grow beyond the colloidal size range, drops or precipitates form, and no colloidal system results. Clouds form when water molecules aggregate and form colloid-sized particles. If these water particles coalesce to form adequately large water drops of liquid water or crystals of solid water, they settle from the sky as rain, sleet, or snow. Many condensation methods involve chemical reactions. A red colloidal suspension of iron(III) hydroxide may be prepared by mixing a concentrated solution of iron(III) chloride with hot water:
\[\ce{Fe^{3+}(aq) + 3 Cl^{-}(aq) + 6 H2O(l) \longrightarrow Fe ( OH )_3(s) + H3O^{+}(aq) + 3 Cl^{-}(aq)} \nonumber \]
A colloidal gold sol results from the reduction of a very dilute solution of gold(III) chloride by a reducing agent such as formaldehyde, tin(II) chloride, or iron(II) sulfate:
\[\ce{Au^{3+} + 3 e^{-} -> Au} \nonumber \]
Some gold sols prepared in 1857 are still intact (the particles have not coalesced and settled), illustrating the long-term stability of many colloids.
Soaps and Detergents
Pioneers made soap by boiling fats with a strongly basic solution made by leaching potassium carbonate, K 2 CO 3 , from wood ashes with hot water. Animal fats contain polyesters of fatty acids (long-chain carboxylic acids). When animal fats are treated with a base like potassium carbonate or sodium hydroxide, glycerol and salts of fatty acids such as palmitic, oleic, and stearic acid are formed. The salts of fatty acids are called soaps . The sodium salt of stearic acid, sodium stearate, has the formula C 17 H 35 CO 2 Na and contains an uncharged nonpolar hydrocarbon chain, the C 17 H 35 — unit, and an ionic carboxylate group, the —
Detergents (soap substitutes) also contain nonpolar hydrocarbon chains, such as C 12 H 25 —, and an ionic group, such as a sulfate—
The cleaning action of soaps and detergents can be explained in terms of the structures of the molecules involved. The hydrocarbon (nonpolar) end of a soap or detergent molecule dissolves in, or is attracted to, nonpolar substances such as oil, grease, or dirt particles. The ionic end is attracted by water (polar), illustrated in Figure \(\PageIndex{5}\). As a result, the soap or detergent molecules become oriented at the interface between the dirt particles and the water so they act as a kind of bridge between two different kinds of matter, nonpolar and polar. Molecules such as this are termed amphiphilic since they have both a hydrophobic (“water-fearing”) part and a hydrophilic (“water-loving”) part. As a consequence, dirt particles become suspended as colloidal particles and are readily washed away.
Chemistry in Everyday Life: Deepwater Horizon Oil Spill
The blowout of the Deepwater Horizon oil drilling rig on April 20, 2010, in the Gulf of Mexico near Mississippi began the largest marine oil spill in the history of the petroleum industry. In the 87 days following the blowout, an estimated 4.9 million barrels (210 million gallons) of oil flowed from the ruptured well 5000 feet below the water’s surface. The well was finally declared sealed on September 19, 2010.
Crude oil is immiscible with and less dense than water, so the spilled oil rose to the surface of the water. Floating booms, skimmer ships, and controlled burns were used to remove oil from the water’s surface in an attempt to protect beaches and wetlands along the Gulf coast. In addition to removal of the oil, attempts were also made to lessen its environmental impact by rendering it “soluble” (in the loose sense of the term) and thus allowing it to be diluted to hopefully less harmful levels by the vast volume of ocean water. This approach used 1.84 million gallons of the oil dispersant Corexit 9527, most of which was injected underwater at the site of the leak, with small amounts being sprayed on top of the spill. Corexit 9527 contains 2-butoxyethanol (C 6 H 14 O 2 ), an amphiphilic molecule whose polar and nonpolar ends are useful for emulsifying oil into small droplets, increasing the surface area of the oil and making it more available to marine bacteria for digestion (Figure \(\PageIndex{6}\)). While this approach avoids many of the immediate hazards that bulk oil poses to marine and coastal ecosystems, it introduces the possibility of long-term effects resulting from the introduction of the complex and potential toxic components of petroleum into the ocean’s food chain. A number of organizations are involved in monitoring the extended impact of this oil spill, including the National Oceanic and Atmospheric Administration (visit this website for additional details).
Electrical Properties of Colloidal Particles
Dispersed colloidal particles are often electrically charged. A colloidal particle of iron(III) hydroxide, for example, does not contain enough hydroxide ions to compensate exactly for the positive charges on the iron(III) ions. Thus, each individual colloidal particle bears a positive charge, and the colloidal dispersion consists of charged colloidal particles and some free hydroxide ions, which keep the dispersion electrically neutral. Most metal hydroxide colloids have positive charges, whereas most metals and metal sulfides form negatively charged dispersions. All colloidal particles in any one system have charges of the same sign. This helps keep them dispersed because particles containing like charges repel each other.
The charged nature of some colloidal particles may be exploited to remove them from a variety of mixtures. For example, the particles comprising smoke are often colloidally dispersed and electrically charged. Frederick Cottrell, an American chemist, developed a process to remove these particles. The charged particles are attracted to highly charged electrodes, where they are neutralized and deposited as dust (Figure \(\PageIndex{8}\)). This is one of the important methods used to clean up the smoke from a variety of industrial processes. The process is also important in the recovery of valuable products from the smoke and flue dust of smelters, furnaces, and kilns. There are also similar electrostatic air filters designed for home use to improve indoor air quality.
Portrait of a Chemist: Frederick Gardner Cottrell
Born in Oakland, CA, in 1877, Frederick Cottrell devoured textbooks as if they were novels and graduated from high school at the age of 16. He then entered the University of California (UC), Berkeley, completing a Bachelor’s degree in three years. He saved money from his $1200 annual salary as a chemistry teacher at Oakland High School to fund his studies in chemistry in Berlin with Nobel prize winner Jacobus Henricus van’t Hoff, and in Leipzig with Wilhelm Ostwald, another Nobel awardee. After earning his PhD in physical chemistry, he returned to the United States to teach at UC Berkeley. He also consulted for the DuPont Company, where he developed the electrostatic precipitator, a device designed to curb air pollution by removing colloidal particles from air. Cottrell used the proceeds from his invention to fund a nonprofit research corporation to finance scientific research.
Gels
Gelatin desserts, such as Jell-O, are a type of colloid (Figure \(\PageIndex{9}\)). Gelatin sets on cooling because the hot aqueous mixture of gelatin coagulates as it cools, yielding an extremely viscous body known as a gel . A gel is a colloidal dispersion of a liquid phase throughout a solid phase. It appears that the fibers of the dispersing medium form a complex three-dimensional network, the interstices being filled with the liquid medium or a dilute solution of the dispersing medium.
Pectin, a carbohydrate from fruit juices, is a gel-forming substance important in jelly making. Silica gel, a colloidal dispersion of hydrated silicon dioxide, is formed when dilute hydrochloric acid is added to a dilute solution of sodium silicate. Canned Heat is a flammable gel made by mixing alcohol and a saturated aqueous solution of calcium acetate.