Overview of Environmental Health Hazards (2024)

Figure

''I was sick and ye visited me." Florence Nightingale at Therafia Hospital, near Constantinople, Turkey.

The most difficult challenges for environmental health today come not from what is known about the harmful effects of microbial agents; rather they come from what is not known about the toxic and ecologic effects of the use of fossil fuels and synthetic chemicals in modern society.

—DHHS, 1990, p. 312

Environmental health hazards are ubiquitous, affecting all aspects of life and all areas of nursing practice. As noted by the National Research Council in 1984, more than 65,000 new chemical compounds have been introduced into the environment since 1950, and new chemical compounds enter commerce each year. The post-World War II era brought major technological advances to society, accompanied by the release of an unprecedented amount of synthetic chemicals onto U.S. markets. It is presently estimated that there are 72,000 chemicals currently used in commerce (excluding food additives, drugs, cosmetics, and pesticides), the majority of which have had limited testing for their effects on human health and the environment (INFORM, 1995). Even less is known about simultaneous exposures to a number of different chemicals, which is how most human contact with chemicals occurs.

As early as 1979, the Surgeon General's Report on Health Promotion and Disease Prevention noted, "There is virtually no major chronic disease to which environmental factors do not contribute, either directly or indirectly" (DHHS, 1979, p. 105). Nevertheless, it is impossible to accurately quantify the burden of morbidity and mortality related to environmental exposures for several reasons: poor compliance with reporting requirements for occupational illness, long latency periods between initial exposure and resulting disease, the inability of health care providers to recognize environmental etiologies of diseases, and the absence of national reporting systems for environmentally related illnesses. The extent of the problem is further obscured by the multifactorial etiology of many environmentally related diseases (e.g., lung cancer caused by exposure to asbestos is more likely to occur among people who smoke tobacco). Nevertheless, the link between adverse health effects and exposure to environmental hazards has been well established, and much can be done to prevent or minimize environmentally related illnesses.

While scientific understanding of the potential adverse health effects of most chemical compounds on humans is incomplete, reports concerning the adverse health affects associated with chemical exposures in other species are frequent. People's concerns about the impact of environmental conditions on their health are often voiced to nurses in the community and at the workplace. However, many nurses do not have the knowledge needed to identify environmental factors that may contribute to illness and injury among the populations they serve.

Environmental hazards may be encountered at home, work, or in the community via several pathways: contaminated air, soil, water, and food (see Figure 2.1). Routes of exposure include: inhalation, such as, of dust or fumes; ingestion, such as, of pesticide residues on fruits and vegetables; and dermal absorption, such as, of ultraviolet-B radiation from the sun or direct skin contact with caustic household cleansers.

FIGURE 2.1

2.1 Exposure pathways. SOURCE: ATSDR, 1992.

This chapter provides an overview of environmental hazards to human health in the home, workplace, community, and globally. It is only an overview, and does not include all environmental hazards or all environmentally related illnesses, nor does it detail all of the hazards to, or specific vulnerabilities of, various subpopulations. It does, however, establish a basis for the need to examine the role of nurses in addressing environmental health issues, particularly for readers who are new to the field of environmental health. Subsequent chapters will link the problems described in this chapter to implications for changes in nursing practice, education, and research to allow for more effective interventions in matters of environmental health.

Classifying Hazards

Although a number of systems are used to characterize environmental hazards, most commonly they are classified as either chemical, physical, mechanical, or psychosocial hazards. Table 2.1 presents this classification scheme, along with examples of hazards that fall into each category. Stevens and Hall (1993) have compiled a list of environmental health problems that are categorized by a variety of broad public health issues (Table 2.2), which is also included to illustrate the range of specific environmental problems that may adversely affect human health.

TABLE 2.1

Common Classes of Environmental Health Hazards, with Examples.

TABLE 2.2

Examples of Environmental Health Hazards.

Air, Soil, and Water

According to EPA, more than 40 million people live within 4 miles of a Superfund¹ site, and approximately 4 million reside within 1 mile of a site (NRC, 1991). Those people who live near Superfund sites may be at risk for exposure to hazardous substances in contaminated drinking water, contaminated soil in such areas as playgrounds and gardens, or through the siting of homes on contaminated property with the possibility of exposure to toxic substances via numerous routes and pathways.

Safe drinking water is a significant environmental health concern: currently 25 percent of community water systems provide drinking water that does not meet EPA safety standards for biological and chemical contaminants (DHHS, 1990). Contaminated drinking water can be a result of point-source pollutants such as Superfund sites or non-point sources such as runoff of agricultural fertilizers and pesticides into waterways that supply drinking water.

The environmental exposure limits designed to protect against contaminants may be in the form of regulatory standards (e.g., maximum contaminant levels (MCLs) for drinking water), action standards (e.g., soil lead levels exceeding 500 ppm), or risk-based standards (e.g., a 10^-4 or 10^-6 excess cancer risk). Environmental standards are often based on retrospective studies of worker exposure (a natural experimental model) or on laboratory studies using animals. A large degree of uncertainty exists when extrapolating from safe levels of exposure for workers based on an 8 hour period within a work site to ambient levels of residential exposure that may occur 24 hours a day outside the worksite (and away from safety systems such as exhaust ventilation). An even greater level of uncertainty and complexity results when studies of small laboratory animals exposed to large quantities of a single substance over a brief period of time are used as the basis for projecting health risk to humans, who are typically exposed to small quantities of multiple substances over extended periods of time.

Air pollution—both indoor and outdoor—raises another set of environmental hazards. Over 50 percent of the U.S. population lives in areas where the outdoor air did not meet EPA standards for contaminants (e.g., ozone, nitrogen dioxide, sulfur dioxide, particulates, and lead) at some time during the previous 12 months (DHHS, 1990). Most Americans spend the majority of their time indoors, either at home, school, or the workplace, where most of the exposure to foreign proteins via inhalation occurs. A large proportion of asthmatics are allergic to indoor allergens, including foreign proteins, and exposure to these allergens can be reduced or minimized through various measures. According to the IOM, improved public and professional education are essential for the prevention and control of indoor allergic disease. Nursing education should emphasize the importance of recognition and proper management of these diseases (IOM, 1993). Paralleling increased pollution of both indoor and outdoor air, the incidence of childhood asthma has risen sharply in the last 2–3 decades. For some age groups (e.g., girls aged 5–14 years) the incidence has doubled or tripled (Yunginger, 1992). In addition, adverse health effects associated with indoor and outdoor air pollution disproportionately affect some populations; asthma mortality rates among African Americans are 3–5 times greater than among Caucasians (IOM, 1993).

Pesticide residues on fruits and vegetables, and the bioaccumulation of chemicals in fish and seafood are additional concerns: it is estimated that 25 percent of all rivers, lakes, and streams in the United States cannot support "beneficial uses," including fishing and swimming, due to widespread pollution (DHHS, 1990). Contaminants with the potential to adversely affect human health include polychlorinated biphenyls (PCBs) and mercury. Disadvantaged populations who consume larger quantities of contaminated fish caught in local waters experience a greater burden of exposure than members of other socioeconomic groups. Nurses working in community and public health settings could assist in educating the public about the hazards (or safety) of diets that consist of fish and seafood taken from local waterways and by explaining appropriate measures for rinsing pesticide residues from fruits and vegetables.

The Workplace Environment

The workplace is an important setting to consider when studying environmentally related illness; environmental hazards and exposures can be substantial in occupational settings. At present, workplace injuries and fatalities are the most well-documented indices of adverse effects of the environment on health. More than 2.25 million work-related illnesses and injuries were reported to the U.S. Department of Labor in 1993 (BLS, April 26, 1995). Three primary occupations with at least 100,000 cases involving work absences²—truck drivers, nonconstruction laborers (except farm), and nursing aides and orderlies—had larger shares of the injury and illness case total for 1993 than their share of the total workforce (BLS, May 15, 1995). Sprains and strains were by far the leading type of injury, and the parts of the body most often affected were the back, shoulder, and other areas of the upper trunk. The three most common injuries or illnesses in terms of number of lost work days were carpal tunnel syndrome (median = 30 lost days), amputation (median = 22 lost days), and fractures (median = 20 lost days). Men accounted for a larger share (two-thirds) of the survey-wide total absences due to injuries and illnesses than their share (55 percent) of total employment. Women injured on the job accounted for a larger share of repetitive motion disorders (64 percent) and injuries from violent acts (57 percent) than their share of total employment (45 percent).

The costs to employers and society of these injuries are high and can be measured in lost work days: 20 percent of injured people were absent from work for 31 days or more. There were 117,000 absences in 1993 from work due to work-related illnesses, including carpal tunnel syndrome and long-term latent diseases, such as skin cancer following exposure to arsenic or ionizing radiation. The incidence of occupational diseases is believed to be understated in the survey because of: (1) the difficulty in relating these illnesses to the workplace, and (2) the failure of health care providers to recognize and report such conditions as being work related (BLS, April 26, 1995).

The Global Environment

In addition to exposures at home, in the workplace, and in the community, global environmental conditions may also adversely affect human health. Global warming trends over the last century may have numerous untoward health effects should they continue. For example, it is estimated that mortality during prolonged heat waves may increase 30 percent-50 percent in U.S. cities if warming trends continue (Kilbourne, 1990). Increases in temperature may adversely affect people with a number of major categories of disease, particularly cardiovascular, cerebrovascular, and respiratory diseases (Haines, 1993). Cardiovascular mortality associated with heat waves of 41°C may be due to a rise in heart rate of about 30 beats per minute and a fall in blood pressure that has been demonstrated under such conditions (Keatinge et al., 1986). Morbidity and mortality due to in infectious diseases may also increase, as some organisms now restricted to tropical areas could invade densely populated areas further north as the planet warms (Chiras, 1994).

Depletion of stratospheric ozone by the release of chlorofluorocarbons (CFCs), which has occurred over the Arctic as well as the Antarctic, leaves large populations worldwide at risk for adverse health effects from overexposure to ultraviolet radiation. On a seasonal basis, ozone-depleted vortices (large air streams) break into clumps and flow from the Antarctic over highly populated areas of Australia, New Zealand, South America, and Africa; from the Arctic, ozone-depleted air flows southward over North America and Europe. During these periods, which last for several months, ultraviolet radiation can increase by as much as 20 percent. Exposure to ultraviolet radiation is associated with a variety of adverse health effects (Miller, 1993). The incidence of melanomas has already increased by 83 percent in the United States during the period from 1982 through 1989, and the incidence of skin cancer will continue to increase with continued depletion of the ozone layer (CDC, 1995; Chivian et al., 1993; Longstreth, 1990). Low-intensity ultraviolet radiation (UV-B) from sunlight also alters T-lymphocyte function, thus suppressing cellular immunity and increasing susceptibility to carcinogenic and infectious agents (Daynes, 1990; Hersey et al., 1983). Studies of fishermen on the Chesapeake Bay have demonstrated an increased risk for cataracts associated with exposure to sunlight, an outcome believed to be related to oxygen free radicals generated by UV-B (Chivian et al., 1993; Hu, 1990; Jacques and Chylack, 1991; Rosenthal et al., 1988; Taylor, 1990).

A number of global environmental conditions have the potential for untoward effects on health, and further research is needed to illuminate these potential outcomes. Nurses who are knowledgeable about global environmental conditions, such as ozone depletion, can educate the public about measures to reduce or eliminate their exposure to such hazards, (e.g., by limiting direct exposure to the sun and through the use of sunglasses that limit transmission of ultraviolet radiation) and measures to limit further global changes that may have adverse effects on human health (e.g., by using public transportation or car-pooling when possible to reduce the production of greenhouse gases).

Vulnerable Populations

Individuals vary widely in their susceptibility to adverse health effects following exposure to toxic substances. Personal characteristics such as age, gender, weight, genetic composition, nutritional status, physiologic status (including pregnancy), preexisting disease states, behavior and lifestyle factors, and concomitant or past exposures may all affect human responses to environmental conditions. The manner in which these characteristics may enhance or decrease susceptibility to environmental hazards is in some cases fairly obvious, while in others it is less so. The relationship of age and genetic factors to one's susceptibility to adverse effects from environmental hazards are perhaps least obvious to clinicians. Table 2.3 summarizes some of the major genetic factors that may be associated with enhanced susceptibility to chemicals in the environment (Tarcher, 1992). The unique vulnerabilities of individuals at the two extremes of the life cycle, that is, young children and the aged, are similar in many ways due either to the immaturity or normal decline in functioning of major physiologic processes.

TABLE 2.3

Genetic Factors and Susceptibility to Occupational and Environmental Chemicals.

Although there are wide individual variations, elderly populations have progressively decreasing function of cardiac, renal, pulmonary, and immune system processes (Tarcher, 1992, p. 198). As a result of these changes—most of which have been documented in the study of drug therapies in the aged—elderly individuals may have impaired host defenses, impaired immune system function, and changes in their ability to detoxify chemicals. Changes in the stratum corneum of the skin can increase the percutaneous absorption of chemicals. Structural and functional changes that occur in the lung with advanced age, including loss of elasticity and impaired ciliary action, can result in more rapid absorption and decreased clearance of foreign substances in the lung. A decline in the metabolic clearance of certain drugs that require oxidative mechanisms for biotransformation has been noted in aged populations that may also result in a decreased ability to detoxify environmental toxins. Declines in blood flow to both liver and kidney, in part due to declining cardiac output estimated at 1 percent annually after the age of 30, may result in a decreased ability to detoxify and eliminate toxic substances from the body among aged populations. Immune system function is also impaired with aging, including a reduction in cell-mediated immunity and T lymphocytes. Finally, a change in body composition occurs with aging; there is a marked increase in adipose tissue mass with a decline in lean body mass. As a result of changes in body composition, water soluble drugs and chemicals have a smaller volume of distribution and greater serum levels, while lipid-soluble substances have an increased volume of distribution. This spectrum of physiologic changes in the aged may increase or decrease both their susceptibility to, and the magnitude of, adverse health outcomes associated with exposure to environmental hazards.

Children are also uniquely susceptible to environmental hazards. They have a higher basal metabolic rate than adults, which affects the absorption and metabolism of toxicants. Children also have a different breathing zone than adults; they are closer to the floor, where dust, dirt, and toxic heavy metals such as lead are deposited. The rapid growth and differentiation of cells in young children leaves them more susceptible to genetic alterations associated with many chemical exposures. An increased rate of cell proliferation can indirectly lead to carcinogenesis by increasing the likelihood that spontaneous mutation will occur or by decreasing the time available to repair DNA damage (NRC, 1993b). Moreover, the normal hand-to-mouth activity of toddlers increases the likelihood of exposure through ingestion of toxic substances. Because some toxicants are retained in ''biologic sanctuaries" (e.g., lead in bone and polycyclic aromatic hydrocarbons in fat), they can cause low-dose chronic exposure for a much longer period of time than would be experienced by exposed adults. Nurses caring for children in any setting—inpatient pediatric units, well-child clinics, home health agencies, and prenatal health centers—need to understand these factors if they are to detect, or more importantly, prevent adverse environmental exposures in children.

It is estimated that 3–4 million U.S. children have blood lead levels above the defined toxic level of 10 mcg/dl, a level known to cause irreversible deficits in attention and IQ scores (ATSDR, 1988; CDC, 1991a; Needleman et al., 1979, 1990). Although lead was banned from household paint in 1971, almost all houses built before 1960 and 20 percent of those built between 1960 and 1974 contain leaded paint (Needleman and Landrigan, 1994). Children at greatest risk for lead poisoning are those living in poorly maintained, substandard housing (e.g., those living in poverty-level conditions). Nurses, including nurse practitioners, must be alert to the risk factors for lead poisoning in young children and aware of measures to reduce those risks. As recommended by the CDC, nurses and other health care providers need to phase-in virtually universal screening of children for blood lead levels (CDC, 1991a). Other environmental hazards in the home that are of concern to both children and adults include radon, environmental tobacco smoke (DHHS, 1986; NRC, 1986), pesticides (Environmental Studies Board, 1988; Miller, 1993; Moses, 1993; Sherman, 1988; Tarcher, 1992), carbon monoxide and airborne particulates from wood-burning stoves (American Thoracic Society, 1990; Samet et al., 1987; Tarcher, 1992), nitrogen dioxide from natural gas stoves (Samet et al., 1987; Tarcher, 1992), formaldehyde and other chemicals that are released as "off-gases" from new carpets, blown-in foam insulation, and synthetic materials covering the indoor surfaces of many mobile homes (Leikauf, 1992; Needleman and Landrigan, 1994; Sherman, 1988; Tarcher, 1992).

Environmental Health Priorities

Priority environmental hazards and environmentally related illnesses have been established by various public and private-sector organizations, including EPA, NIOSH, and the Agency for Toxic Substances and Disease Registry (ATSDR). A description of priority health conditions that were established by ATSDR is presented here as an example.

ATSDR is an agency of the U.S. Public Health Service responsible for investigating health effects related to hazardous wastes. ATSDR (Lybarger et al., 1993) classifies hazardous substances according to adverse health outcomes associated with a substance; their priority health conditions include:

birth defects and reproductive disorders,
cancer,
immune function disorders,
kidney and liver dysfunction,
lung and respiratory diseases, and
neurotoxic disorders.

ATSDR uses their priority health conditions to guide the use of resources in the evaluation of community health risks, in establishing health education programs, and in preventing or mitigating adverse health effects resulting from exposure to hazardous environmental agents. ATSDR's 10 leading priority environmental hazards are listed in Table 2.4.

TABLE 2.4

Agency for Toxic Substances and Disease Registry 1993 Priority List of Rank Ordered Top 10 Hazardous Substances.

Conclusion

In conclusion, a large spectrum of environmental agents are potential health hazards. Some of these are common, others are not; some are apparent, others are not. All are important, however, and nurses need to be aware of them in their daily practice to improve the level of health care they provide. To this end, the remainder of the report addresses various aspects of enhancing environmental health in nursing practice, education, and research.

1: Superfund sites are hazardous waste sites designated by the U.S. Environmental Protection Agency (EPA) as a threat to human health. These areas may include leaking underground storage tanks or inactive hazardous waste sites such as municipal dumps and contaminated factories or mines and mills (Chiras, 1994).
2: An "absence" is defined as one or more work days lost due to a single episode of occupational injury or illness. Thus, five lost work days due to a sprained ankle equals one absence.