Environmental illnesses

DEFINITION: Ailments caused by exposure to chemical agents, radiation, physical hazards, and nature’s reactions to invasions by humankind

With growing awareness of the illnesses that can be caused by exposure to certain elements in the environment have come the passage of legislation and increasing support for regulations designed to protect human health. Workplace-related environmental illnesses have come under particular scrutiny in the United States.

Environmental illnesses—a category of ailments that includes occupational illnesses—are noninfectious and infectious diseases caused by environmental exposures, in addition to injuries caused by physical hazards considered beyond the immediate control of the individual. Nonoccupational environmental diseases identified by the US Department of Health and Human Services include asthma, heatstroke, hypothermia, heavy metal poisoning, pesticide poisoning, carbon monoxide poisoning, acute chemical poisoning, and methemoglobinemia.

Physicians in ancient Egypt noted environmental conditions that had negative impacts on health, and some historians believe that lead poisoning was a strong contributor to the fall of the Roman Empire in 476 CE. Awareness of environmental illnesses intensified during the Industrial Revolution with the realization that some diseases were strongly associated with specific occupational settings. Some early examples include silicosis, a lung disease contracted by large numbers of industrial workers, miners, and potters who were exposed to silica dust, and a delayed form of bone disease in laborers working within manufacturing plants that contained phosphorus.

Most industrialized countries had implemented early forms of environmental protection laws by the 1920s, but the increased use of caustic chemicals and radioactive materials made research involving ecology (scientific study of how living organisms are affected by their environment) increasingly complex. The ecology of infection involves interactions among the climate (as shown by the seasonal increases in influenza and pneumonia); contaminated air, water, and food; and nature itself, with many serious diseases such as tuberculosis, cholera, malaria, and typhoid fever significantly decreasing in incidence upon implementation of appropriate changes within the environment.

Environmental illnesses can affect every organ and system of the body in both mild and severe forms, with diagnosis made more difficult when specific exposures cannot be identified or when symptoms of the illness are delayed. The onset of some disease symptoms occurs immediately, but many symptoms do not appear until long after exposure; some forms of cancer, for example, have latency periods exceeding thirty years. Epidemiological studies of exposed populations are complicated by the fact that clinical features are often nonspecific. Furthermore, many illnesses can be enhanced by both the environment and personal habits, such as smoking and medication abuse.

Chemical Agents

Environmental hazards that influence health and disease processes include natural stressors such as heat, cold, altitude, relative humidity, and wind speed. Unnatural environmental illnesses are created by humans rather than by nature and are generally caused by one of three factors: chemical agents, radiation, or human-made physical hazards. Exposure routes include direct or indirect contact with toxins and contaminated air, water, and food. Risk is greatly increased when multiple toxic agents act together, as illustrated by the increased risk of lung cancer in asbestos workers who also smoke or inhale secondhand smoke. Toxic waste dumps pose considerable environmental risks, as they can expose people to multiple hazardous chemicals simultaneously. Thousands of hazardous chemicals have been introduced into the environment with advances in industry; common inorganic examples include Dichloro-diphenyl-trichloroethane (DDT), vinyl chloride, and polychlorinated biphenyls (PCBs), and common organic examples include asbestos, mercury, lead, and arsenic.

The pesticide DDT is the most widely referenced example of the danger of introducing synthetic compounds into the environment before long-term effects have been researched. Used for years following World War II, DDT contributed to significant declines in malaria worldwide. The compound is not easily biodegradable, however, and persists in the environment for years. The use of DDT was eventually banned in nearly all developed countries following the detection of the chemical in essentially every living organism tested. Many other agricultural pesticides are designed to deter or eliminate weeds, insects, fungi, or rodents that pose a threat to crops. When these toxins drift with the wind or are absorbed into the crops they are designed to protect, illnesses such as cancer and congenital anomalies can result, with their extent related to dosage and exposure duration. Many chemicals and chemical combinations have the potential to produce delayed forms of cancer. For example, exposure to asbestos may lead to lung cancer and mesothelioma, vinyl chloride may cause liver cancer, and benzene may cause leukemia. The expression of diseases that come from chemical agents and radiation depends on agent entry into the body, metabolic processes within the body, routes by which the body attempts to excrete the substance, and medical treatments.

Airborne pollutants have a much greater influence on the body during physical exertion than during rest because the increased rate and depth of breathing during exertion exposes more particulate matter to the delicate tissues of the lungs. Physical work requires a transition from nose breathing to mouth breathing, with inhaled air thus bypassing the body’s natural air-purifying system in the nasal hairs and mucous membranes, which are generally very effective at removing pollutants at low ventilation rates. Tiny particulates are more dangerous than larger particles because they are not trapped in the upper respiratory tract, they attach solidly to alveoli in the lungs, and they cannot be effectively exhaled.

Ozone is extremely toxic to humans, causing lung irritation, chest pain, bronchospasm, headaches, and nausea. Long periods of breathing ozone combined with hydrocarbons, aerosols, and sulfur and nitrogen dioxide are contributing factors to allergies, asthma, cardiovascular disease, emphysema, bronchitis, and lung cancer. Temperature inversions in cities located at high altitudes and in basins surrounded by mountains that block winds and trap pollutants produce a greenhouse effect. Temperature inversions cause a reversal of the normal atmospheric temperature gradient, which heats the harmful chemicals, thus enhancing their effects on the body. For example, the strong eastern winds blowing toward Denver, Colorado, trap a brown cloud of pollutants against the Rocky Mountains, requiring the daily broadcasting of air-quality reports for sensitive persons, such as older adults and people with cardiorespiratory conditions, who are often advised to stay indoors when the air quality is poor.

Radiation, Physical Hazards, and Nature

Ever since the 1945 atomic bomb attack on Hiroshima, Japan, scientists have become increasingly concerned about the health effects of radioactive pollution. Even small-scale testing of nuclear weapons directly affects the environment, a realization that led the United States, Great Britain, and the Soviet Union to sign the Limited Test Ban Treaty in 1963. Both ionizing and non-ionizing radiation can cause acute and chronic health problems, such as chromosome damage, with workers continually exposed to radioactive metals and X-rays being most susceptible. The 1986 Chernobyl nuclear plant malfunction in the Soviet Union, among the worst peacetime nuclear disasters in history, caused cancer, congenital anomalies, and skin disease among those exposed to radiation. The disposal of nuclear wastes also poses health concerns, given that many radioactive substances have a half-life of more than ten thousand years. Similarly, radioactive particles polluted the water and air following Japan's 2011 nuclear accident at the Fukushima Daiichi nuclear plant. Though this incident was not as deadly as Chernobyl, it significantly influenced discussions regarding radiation safety.

The predominant source of physical hazards that cause environmental illnesses is human-made environments that increase the incidence of traumatic injuries and create noise pollution. Accidents occurring in unsafe work surroundings account for a large proportion of preventable injuries. Noise in the workplace can cause hearing loss, the most prevalent occupational impairment, which can progress to permanent hearing loss. Health problems related to noise pollution have increased over time among musicians and their audiences, as well as in urban environments where the constant din of traffic and construction contributes to illnesses such as headaches, depression, and insomnia.

Nature can also cause illnesses as it responds to ecological imbalances introduced by human beings; examples are rabies, giardiasis, Rocky Mountain spotted fever, Lyme disease, and the diseases caused by hantaviruses. Hantaviruses do not cause obvious illness in their rodent hosts, but their effects are transmitted to humans who inhale dust or mist containing dried traces of the urine or feces of infected animals. Hantaviruses are distant cousins of the fearsome Ebola virus, and hantavirus outbreaks must be handled much like outbreaks of hepatitis. Rabies is transmitted to humans through bites or scratches containing the saliva of rabid animals such as infected dogs or bats. The disease attacks the nervous system. Giardiasis is a nonbacterial intestinal illness caused by a parasite found in untreated or improperly treated surface water taken from streams and lakes. Symptoms of infection include diarrhea, nausea, reduced appetite, abdominal cramps, bloated stomach, and fatigue.

The symptoms of Rocky Mountain spotted fever, an infection caused by a dog tick, are fever, headache, rash, and nausea. As the infection progresses, the original red spots may change in appearance to look more like bruises or bloody patches under the skin. Lyme disease was classified following a mysterious juvenile arthritis outbreak. Spread exclusively through bites from infected ticks, its early stages are marked by fatigue, malaise, chills, fever, headaches, muscle and joint pain, swollen lymph nodes, and skin rashes. Later stages may include arthritis, nervous system abnormalities, and heart conduction disturbances.

Climate change is having an impact on human health. Extreme weather events such as heatwaves and floods have become more common. These events increase the risk of food-borne and water-borne diseases. For example, coastal flooding often results in many cases of malaria. According to the World Health Organization (WHO), 600 million people contract food-borne illnesses annually. Furthermore, climate change affects the availability, diversity, and quality of food available to populations, which can lead to malnutrition and increase individuals' susceptibility to illness.

Agencies and Legislation

Agencies that have federal authority to investigate environmental issues related to disease in the United States include the Department of Labor, under which fall the Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA), and the Department of Health and Human Services, under which fall the Food and Drug Administration (FDA), the National Institutes of Health (NIH), the Centers for Disease Control and Prevention (CDC), and the Health Resources and Services Administration (HRSA). The National Institute for Occupational Safety and Health (NIOSH) conducts ongoing research to identify hazards and develop safety standards, and many large companies now employ industrial health advisers.

The World Health Organization (WHO), founded in 1948 as an agency of the United Nations, provides international coordination regarding environmental and occupational health concerns. WHO is extremely active in developing countries as industrialization, poverty, and population growth continue to increase. Its broad scope of activities includes controlling widespread diseases such as malaria and tuberculosis, establishing purified water supplies and sanitation systems, and providing health education and health planning assistance.

During the 1960s, the US Congress increasingly took up legislation intended to regulate workplace practices and sources of pollution that could lead to environmental illnesses. Federal laws that remain the most relevant include the Occupational Safety and Health Act of 1970, the Federal Environmental Pesticide Control Act of 1972, the Toxic Substances Control Act of 1976, the Resource Conservation and Recovery Act of 1976, and the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA; also known as Superfund). In 1985, several “right to know” laws went into effect; these laws require the managers of manufacturing plants to supply employees with health and safety information regarding toxic materials.

To further protect Americans from environmental illnesses, the EPA enacted the 2021 PFAS (Per- and Polyfluoroalkyl Substances) Strategic Roadmap, which detailed a plan to address PFAS between 2021 and 2024. The same year, the PFAS Action Act created incentives and requirements to limit PFAS use and contamination.

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