6 Environmental Toxins: What are you Exposed to!
Types of environmental hazards:
Environmental health is defined as the assessment of environmental factors that influence human health and quality of life, and steps taken to avoid environmental hazards or minimize its effects. There are 4 major types of environmental hazards:
- Physical e.g. Earthquakes, volcanoes, fires, floods, droughts, lightning, hurricanes, landslides,
- Chemical synthetic (man-made) (e.g. pesticides, disinfectants, pharmaceuticals) or natural chemicals (e.g. venom from cobras, urushiol in poison ivy)
- Biological e.g. bacterial infections from E. coli, parasites like malaria, viruses like the flu
- Cultural lifestyle based e.g. smoking, diet and nutrition, activity level
Environmental Toxicology
Environmental toxicology is the scientific study of the health effects associated with exposure to toxic chemicals and systems occurring in the natural, work, and living environments; the management of environmental toxins and toxicity; and the development of protections for humans, animals, and plants (Table below).
The table below lists top 20 substances, in order of priority, which are determined to pose the most significant potential threat to human health.This priority list is not a list of “most toxic” substances, but rather a prioritization of substances based on a combination of their frequency, toxicity, and potential for human exposure at various sites.
| 2013 RANK |
NAME |
|---|---|
| 1 | ARSENIC |
| 2 | LEAD |
| 3 | MERCURY |
| 4 | VINYL CHLORIDE |
| 5 | POLYCHLORINATED BIPHENYLS |
| 6 | BENZENE |
| 7 | CADMIUM |
| 8 | BENZO(A)PYRENE |
| 9 | POLYCYCLIC AROMATIC HYDROCARBONS |
| 10 | BENZO(B)FLUORANTHENE |
| 11 | CHLOROFORM |
| 12 | AROCLOR 1260 |
| 13 | DDT, P,P’- |
| 14 | AROCLOR 1254 |
| 15 | DIBENZO(A,H)ANTHRACENE |
| 16 | TRICHLOROETHYLENE |
| 17 | CHROMIUM, HEXAVALENT |
| 18 | DIELDRIN |
| 19 | PHOSPHORUS, WHITE |
| 20 | HEXACHLOROBUTADIENE |
Routes of Exposure to Chemicals
In order to cause health problems, chemicals must enter your body. There are three main “routes of exposure,” or ways a chemical can get into your body.
- Breathing (inhalation): Breathing in chemical gases, mists, or dusts that are in the air.
- Skin or eye contact: Getting chemicals on the skin, or in the eyes. They can damage the skin, or be absorbed through the skin into the bloodstream.
- Swallowing (ingestion): This can happen when chemicals have spilled or settled onto food, beverages, cigarettes, beards, or hands.
Once chemicals have entered your body, some can move into your bloodstream and reach internal “target” organs, such as the lungs, liver, kidneys, or nervous system.
What Forms do Chemicals Take?
Chemical substances can take a variety of forms. They can be in the form of solids, liquids, dusts, vapors, gases, fibers, mists and fumes. The form a substance is in has a lot to do with how it gets into your body and what harm it can cause. A chemical can also change forms. For example, liquid solvents can evaporate and give off vapors that you can inhale. Sometimes chemicals are in a form that can’t be seen or smelled, so they can’t be detected.
Detecting some forms of chemicals can be difficult. Solids and liquids are easier to recognize since they can be seen. Dusts and mists may or may not be visible, depending upon their size and concentration. Fumes, vapors, and gases are usually invisible.
What Health Effects Can Chemicals Cause?
An acute effect of a contaminant (The term “contaminant” means hazardous substances, pollutants, pollution, and chemicals) is one that occurs rapidly after exposure to a large amount of that substance. A chronic effect of a contaminant results from exposure to small amounts of a substance over a long period of time. In such a case, the effect may not be immediately obvious. Chronic effect are difficult to measure, as the effects may not be seen for years. Long-term exposure to cigarette smoking, low level radiation exposure, and moderate alcohol use are all thought to produce chronic effects.
For centuries, scientists have known that just about any substance is toxic in sufficient quantities. For example, small amounts of selenium are required by living organisms for proper functioning, but large amounts may cause cancer. The effect of a certain chemical on an individual depends on the dose (amount) of the chemical. This relationship is often illustrated by a dose-response curve which shows the relationship between dose and the response of the individual. Lethal doses in humans have been determined for many substances from information gathered from records of homicides and accidental poisonings.
Much of the dose-response information also comes from animal testing. Mice, rats, monkeys, hamsters, pigeons, and guinea pigs are commonly used for dose-response testing. A population of laboratory animals is exposed to measured doses under controlled conditions and the effects noted and analyzed. Animal testing poses numerous problems, however. For instance, the tests may be painful to animals, and unrelated species can react differently to the same toxin. In addition, the many differences between test animals and humans makes extrapolating test results to humans very difficult. A dose that is lethal to 50 percent of a population of test animals is called the lethal dose-50 percent or LD-50. Determination of the LD-50 is required for new synthetic chemicals in order to give a measure of their toxicity. A dose that causes 50 percent of a population to exhibit any significant response (e.g., hair loss, stunted development) is referred to as the effective dose-50 percent or ED-50. Some toxins have a threshold amount below which there is no apparent effect on the exposed population.
Some scientists believe that all toxins should be kept at a zero-level threshold because their effects at low levels are not well known. That is because of the synergy effect in which one substance exacerbates the effects of another. For example, if cigarette smoking increases lung cancer rates 20 times and occupational asbestos exposure also increases lung cancer rates 20 times, then smoking and working in an asbestos plant may increase lung cancer rates up to 400 times.
Environmental Contaminants
The contamination of the air, water, or soil with potentially harmful substances can affect any person or community. Contaminants (Table below) are often chemicals found in the environment in amounts higher than what would be there naturally. We can be exposed to these contaminants from a variety of residential, commercial, and industrial sources. Sometimes harmful environmental contaminants occur biologically, such as mold or a toxic algae bloom.
| Contaminant | Definition |
|---|---|
| Carcinogen | An agent which may produce cancer (uncontrolled cell growth), either by itself or in conjunction with another substance. Examples include formaldehyde, asbestos, radon, vinyl chloride, and tobacco. |
| Suspect Carcinogen | An agent which is suspected of being a carcinogen based on chemical structure, animal research studies, or mutagenicity studies. |
|
Confirmed Animal Carcinogen with Unknown Relevance to Humans |
An agent that is carcinogenic in experimental animals at a relatively high dose, by routes of administration, at sites, or histologic types, or by mechanisms that may not be relevant to worker exposure. Available epidemiologic studies do not confirm an increased risk of cancer in exposed humans. Available evidence does not suggest that the agent is likely to cause cancer in humans except under uncommon or unlikely routes or levels of exposure. |
| Teratogen |
A substance which can cause physical defects in a developing embryo. Examples include alcohol and cigarette smoke. |
| Mutagen | A material that induces genetic changes (mutations) in the DNA. Examples include radioactive substances, x-rays and ultraviolet radiation. |
| Neurotoxicant | A substance that can cause an adverse effect on the chemistry, structure or function of the nervous system. Examples include lead and mercury. |
|
Endocrine disruptor |
A chemical that may interfere with the body’s endocrine system and produce adverse developmental, reproductive, neurological, and immune effects in both humans and wildlife. A wide range of substances, both natural and man-made, are thought to cause endocrine disruption, including pharmaceuticals, dioxin and dioxin-like compounds, arsenic, polychlorinated biphenyls (PCBs), DDT and other pesticides, and plasticizers such as bisphenol A (BPA). Endocrine disruptors may be found in many everyday products– including plastic bottles, metal food cans, detergents, flame retardants, food, toys, cosmetics, and pesticides. Research shows that endocrine disruptors may pose the greatest risk during prenatal and early postnatal development when organ and neural systems are forming. |
The following are some environmental contaminants that can affect a community or an individual’s health.
Arsenic is a naturally occurring element that is normally present throughout our environment in water, soil, dust, air, and food. Levels of arsenic can vary from place to place due to farming and industrial activity as well as natural geological processes. The arsenic from farming and smelting tends to bind strongly to soil and is expected to remain near the surface of the land for hundreds of years as a long-term source of exposure. Wood that has been treated with chromated copper arsenate (CCA) is commonly found in decks and railing in existing homes and outdoor structures such as playground equipment. Some underground aquifers are located in rock or soil that has naturally high arsenic content.
Most arsenic gets into the body through ingestion of food or water. Arsenic in drinking water is a problem in many countries around the world, including Bangladesh, Chile, China, Vietnam, Taiwan, India, and the United States. Arsenic may also be found in foods, including rice and some fish, where it is present due to uptake from soil and water. It can also enter the body by breathing dust containing arsenic, or through the skin, though this is not a major route of exposure. Researchers are finding that arsenic, even at low levels, can interfere with the body’s endocrine system. In several cell culture and animal models, arsenic has been found to act as an endocrine disruptor, which may underlie many of its health effects. Arsenic is also a known human carcinogen associated with skin, lung, bladder, kidney, and liver cancer.
Polychlorinated biphenyls, commonly called PCBs, are mixtures of up to 209 chlorinated compounds that do not occur naturally. They have no taste or smell. PCBs are persistent organic pollutants (POPs) and endocrine disruptors. The manufacture of PCBs was stopped in the U.S. in 1977 because of evidence they build up in the environment and can cause harmful health effects. But, before 1977, PCBs were used as insulation, as plasticizers, and in surface coatings, sealants, fire retardants, glues, inks, pesticides, and carbonless copy paper. PCBs don’t break down easily in the environment and may remain there for very long periods of time. Studies indicate that PCBs are associated with certain kinds of cancer in humans. Women who were exposed to relatively high levels of PCBs in the workplace or ate large amounts of fish contaminated with PCBs had babies that weighed slightly less than babies from women who did not have these exposures.
Per- and Polyfluoroalkyl Substances (PFAS)
Per- and polyfluoroalkyl substances (PFAS) are a diverse group of thousands of chemicals used in hundreds of types of products. PFAS in the environment can enter the food supply through plants and animals grown, raised, or processed in contaminated areas. It is also possible for very small amounts of PFAS to enter foods through food packaging, processing, and cookware. And most recently, PFAS have been detected in most of the U.S. water supply ( see chapter Water: Necessary for Life).
However, A recent investigation by the Food and Drug Administration found toxic per- and poly- fluoroalkyl substances, or PFAS, in food, including meat, seafood and dairy products; sweet potatoes; pineapples; leafy greens, and chocolate cake with icing. Exposure to PFAS chemicals is associated with serious health risks, including cancer, reproductive harm, developmental harm, high cholesterol, damage to the immune system, hormone disruption, and liver and kidney damage. (ewg)
Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS), for example, are two of the most widely used and studied chemicals in the PFAS group. PFOA and PFOS have been replaced in the United States with other PFAS in recent years. One common characteristic of concern of PFAS is that many break down very slowly and can build up in people, animals, and the environment over time.
PFAS can be present in our water, soil, air, and food as well as in materials found in our homes or workplaces, including:
- Drinking water – in public drinking water systems and private drinking water wells.
- Soil and water at or near waste sites – at landfills, disposal sites, and hazardous waste sites such as those that fall under the federal Superfund and Resource Conservation and Recovery Act programs.
- Fire extinguishing foam – in aqueous film-forming foams (or AFFFs) used to extinguish flammable liquid-based fires. Such foams are used in training and emergency response events at airports, shipyards, military bases, firefighting training facilities, chemical plants, and refineries.
- Manufacturing or chemical production facilities that produce or use PFAS – for example at chrome plating, electronics, and certain textile and paper manufacturers.
- Food – for example in fish caught from water contaminated by PFAS and dairy products from livestock exposed to PFAS.
- Food packaging – for example in grease-resistant paper, fast food containers/wrappers, microwave popcorn bags, pizza boxes, and candy wrappers.
- Household products and dust – for example in stain and water-repellent used on carpets, upholstery, clothing, and other fabrics; cleaning products; non-stick cookware; paints, varnishes, and sealants.
- Personal care products – for example in certain shampoo, dental floss, and cosmetics.
- Biosolids – for example fertilizer from wastewater treatment plants that is used on agricultural lands can affect ground and surface water and animals that graze on the land.
Due to their widespread production and use, as well as their ability to move and persist in the environment, surveys conducted by the Centers for Disease Control and Prevention (CDC) show that most people in the United States have been exposed to some PFAS. Most known exposures are relatively low, but some can be high, particularly when people are exposed to a concentrated source over long periods of time. Some PFAS chemicals can accumulate in the body over time.
Current research has shown that people can be exposed to PFAS by:
- Working in occupations such as firefighting or chemicals manufacturing and processing.
- Drinking water contaminated with PFAS.
- Eating certain foods that may contain PFAS, including fish.
- Swallowing contaminated soil or dust.
- Breathing air containing PFAS.
- Using products made with PFAS or that are packaged in materials containing PFAS.
Current scientific research suggests that exposure to certain PFAS may lead to adverse health outcomes. However, research is still ongoing to determine how different levels of exposure to different PFAS can lead to a variety of health effects. Research is also underway to better understand the health effects associated with low levels of exposure to PFAS over long periods of time, especially in children.
What We Know about Health Effects
Current peer-reviewed scientific studies have shown that exposure to certain levels of PFAS may lead to:
- Reproductive effects such as decreased fertility or increased high blood pressure in pregnant women.
- Developmental effects or delays in children, including low birth weight, accelerated puberty, bone variations, or behavioral changes.
- Increased risk of some cancers, including prostate, kidney, and testicular cancers.
- Reduced ability of the body’s immune system to fight infections, including reduced vaccine response.
- Interference with the body’s natural hormones.
- Increased cholesterol levels and/or risk of obesity.
Scientists at EPA, in other federal agencies, and in academia and industry are continuing to conduct and review the growing body of research about PFAS. However, health effects associated with exposure to PFAS are difficult to specify for many reasons, such as:
- There are thousands of PFAS with potentially varying effects and toxicity levels, yet most studies focus on a limited number of better known PFAS compounds.
- People can be exposed to PFAS in different ways and at different stages of their life.
- The types and uses of PFAS change over time, which makes it challenging to track and assess how exposure to these chemicals occurs and how they will affect human health.
Adults
Some people have higher exposures to PFAS than others because of their occupations or where they live. For example:
- Industrial workers who are involved in making or processing PFAS or PFAS-containing materials, or people who live or recreate near PFAS-producing facilities, may have greater exposure to PFAS.
- Pregnant and lactating women tend to drink more water per pound of body weight than the average person and as a result they may have higher PFAS exposure compared to other people if it is present in their drinking water.
Children
Because children are still developing, they may be more sensitive to the harmful effects of chemicals such as PFAS. They can also be exposed more than adults because:
- Children drink more water, eat more food, and breathe more air per pound of body weight than adults, which can increase their exposure to PFAS.
- Young children crawl on floors and put things in their mouths which leads to a higher risk of exposure to PFAS in carpets, household dust, toys, and cleaning products.
Breast milk from mothers with PFAS in their blood and formula made with water containing PFAS can expose infants to PFAS, and it may also be possible for children to be exposed in utero during pregnancy. Scientists continue to do research in this area. Based on current science, the benefits of breastfeeding appear to outweigh the risks for infants exposed to PFAS in breast milk. To weigh the risks and benefits of breastfeeding, mothers should contact their doctors.
Mercury is a naturally occurring metal, a useful chemical in some products, and a potential health risk. Mercury exists in several forms – the types people are usually exposed to are methylmercury and elemental mercury. Elemental mercury at room temperature is a shiny, silver-white liquid, which can produce a harmful odorless vapor. Methylmercury, an organic compound, can build up in the bodies of long-living, predatory fish. To keep mercury out of the fish we eat and the air we breathe, it’s important to take mercury-containing products to a hazardous waste facility for disposal. Common products sold today that contain small amounts of mercury include fluorescent lights and button-cell batteries.
Although fish and shellfish have many nutritional benefits, consuming large quantities of fish increases a person’s exposure to mercury. Pregnant women who eat fish high in mercury on a regular basis run the risk of permanently damaging their developing fetuses. Children born to these mothers may exhibit motor difficulties, sensory problems and cognitive deficits. The poster below (published by the Maine Center for Disease Control & Prevention) identifies the typical (average) amounts of mercury in commonly consumed commercial and sport-caught fish.
Bisphenol A (BPA) is a chemical produced in large quantities for use primarily in the production of polycarbonate plastics and epoxy resins. Polycarbonate plastics have many applications including use in some food and drink packaging, e.g., water and infant bottles, compact discs, impact-resistant safety equipment, and medical devices. Epoxy resins are used as lacquers to coat metal products such as food cans, bottle tops, and water supply pipes. Some dental sealants and composites may also contribute to BPA exposure. The primary source of exposure to BPA for most people is through the diet. Bisphenol A can leach into food from the protective internal epoxy resin coatings of canned foods and from consumer products such as polycarbonate tableware, food storage containers, water bottles, and baby bottles. The degree to which BPA leaches from polycarbonate bottles into liquid may depend more on the temperature of the liquid or bottle, than the age of the container. BPA can also be found in breast milk.
What can I do to prevent exposure to BPA?
Some animal studies suggest that infants and children may be the most vulnerable to the effects of BPA. Parents and caregivers, can make the personal choice to reduce exposures of their infants and children to BPA:
- Don’t microwave polycarbonate plastic food containers. Polycarbonate is strong and durable, but over time it may break down from over use at high temperatures.
- Plastic containers have recycle codes on the bottom. Some, but not all, plastics that are marked with recycle codes 3 or 7 may be made with BPA.
- Reduce your use of canned foods.
- When possible, opt for glass, porcelain or stainless steel containers, particularly for hot food or liquids.
- Use baby bottles that are BPA free.
Dioxins are a class of chemical contaminants that are formed during combustion processes such as waste incineration, forest fires, and backyard trash burning, as well as during some industrial processes such as paper pulp bleaching and herbicide manufacturing. The highest environmental concentrations of dioxin are usually found in soil and sediment, with much lower levels found in air and water. We are primarily exposed to dioxins by eating food contaminated by these chemicals. Studies have also shown that chemical workers who are exposed to high levels of dioxins have an increased risk of cancer. Other studies of show that dioxins can cause reproductive and developmental problems, and an increased risk of heart disease and diabetes.
Phthalates are a group of chemicals used to soften and increase the flexibility of plastic and vinyl. Polyvinyl chloride is made softer and more flexible by the addition of phthalates. Phthalates are used in hundreds of consumer products. Phthalates are used in cosmetics and personal care products, including perfume, hair spray, soap, shampoo, nail polish, and skin moisturizers. They are used in consumer products such as flexible plastic and vinyl toys, shower curtains, wallpaper, vinyl miniblinds, food packaging, and plastic wrap. Exposure to low levels of phthalates may come from eating food packaged in plastic that contains phthalates or breathing dust in rooms with vinyl miniblinds, wallpaper, or recently installed flooring that contain phthalates. We can be exposed to phthalates by drinking water that contains phthalates. Phthalates are suspected to be endocrine disruptors.
Lead is a metal that occurs naturally in the rocks and soil of the earth’s crust. It is also produced from burning fossil fuels such as coal, oil, gasoline, and natural gas; mining; and manufacturing. Lead has no distinctive taste or smell. The chemical symbol for elemental lead is Pb. Lead is used to produce batteries, pipes, roofing, scientific electronic equipment, military tracking systems, medical devices, and products to shield X-rays and nuclear radiation. It is used in ceramic glazes and crystal glassware. Because of health concerns, lead and lead compounds were banned from house paint in 1978; from solder used on water pipes in 1986; from gasoline in 1995; from solder used on food cans in 1996; and from tin-coated foil on wine bottles in 1996. The U.S. Food and Drug Administration has set a limit on the amount of lead that can be used in ceramics.
Lead and lead compounds are listed as “reasonably anticipated to be a human carcinogen”. It can affect almost every organ and system in your body. It can be equally harmful if breathed or swallowed. The part of the body most sensitive to lead exposure is the central nervous system, especially in children, who are more vulnerable to lead poisoning than adults. A child who swallows large amounts of lead can develop brain damage that can cause convulsions and death; the child can also develop blood anemia, kidney damage, colic, and muscle weakness. Repeated low levels of exposure to lead can alter a child’s normal mental and physical growth and result in learning or behavioral problems. Exposure to high levels of lead for pregnant women can cause miscarriage, premature births, and smaller babies. Repeated or chronic exposure can cause lead to accumulate in your body, leading to lead poisoning.
Polyvinyl chloride (PVC) is an odorless and solid plastic. It is most commonly white but can also be colorless or amber. It can also come in the form of white powder or pellets. PVC is made from vinyl chloride. PVC is made softer and more flexible by the addition of phthalates. Bisphenol A (BPA) is also used to make PVC plastics. PVC contains high levels of chlorine. PVC is used to make pipes, pipe fittings, pipe conduits, vinyl flooring, and vinyl siding. When softened with phthalates, PVC is used to make some medical devices (including intravenous (IV) bags, blood bags, blood and respiratory tubing) and consumer products (raincoats, toys, shower curtains, furniture, carpet backing, plastic bags and credit cards). Most vinyl chloride produced in the United States is used to make PVC.
Exposure to PVC often includes exposure to phthalates, which are used to soften PVC and may have adverse health effects. Because of PVC’s heavy chlorine content, dioxins are released during the manufacturing, burning, or landfilling of PVC. Exposure to dioxins can cause reproductive, developmental, and other health problems, and at least one dioxin is classified as a carcinogen. Dioxins, phthalates, and BPA are suspected to be endocrine disruptors, which are chemicals that may interfere with the production or activity of hormones in the human endocrine system.
Formaldehyde is a colorless, flammable gas or liquid that has a pungent, suffocating odor. It is a volatile organic compound, which is an organic compound that easily becomes a vapor or gas. It is also naturally produced in small, harmless amounts in the human body. The primary way we can be exposed to formaldehyde is by breathing air containing it. Releases of formaldehyde into the air occur from industries using or manufacturing formaldehyde, wood products (such as particle-board, plywood, and furniture), automobile exhaust, cigarette smoke, paints and varnishes, and carpets and permanent press fabrics. Nail polish, and commercially applied floor finish emit formaldehyde.
In general, indoor environments consistently have higher concentrations than outdoor environments, because many building materials, consumer products, and fabrics emit formaldehyde. Levels of formaldehyde measured in indoor air range from 0.02–4 parts per million (ppm). Formaldehyde levels in outdoor air range from 0.001 to 0.02 ppm in urban areas.
Radiation
Radiation is energy given off by atoms and is all around us. We are exposed to radiation every day from natural sources like soil, rocks, and the sun. We are also exposed to radiation from man-made sources like medical X-rays and smoke detectors. We’re even exposed to low levels of radiation on cross-country flights, from watching television, and even from some construction materials. You cannot see, smell or taste radiation. Some types of radioactive materials are more dangerous than others. So it’s important to carefully manage radiation and radioactive substances to protect health and the environment.
Radon is a colorless, odorless radioactive gas. It comes from the natural decay of uranium or thorium found in nearly all soils. It typically moves up through the ground and into the home through cracks in floors, walls and foundations. It can also be released from building materials or from well water. Radon breaks down quickly, giving off radioactive particles. Long-term exposure to these particles can lead to lung cancer. Radon is the leading cause of lung cancer among nonsmokers, according to the U.S. Environmental Protection Agency, and the second leading cause behind smoking.
Risk Assessment and Management
Risk assessment is a scientific process used by federal agencies and risk management decision-makers to make informed decisions about actions that may be taken to protect human health by ascertaining potential human health risks or health hazard associated with exposure to chemicals in the environment. Some of the real-world examples of risk assessment includes: establishment of national ambient air quality and drinking water standards for protection of public health (e.g. ozone, particulate matter in outdoor air; chromium, chloroform or benzene in water); establishment of clean-up levels for hazardous waste site remediation; development of fish consumption advisories for pregnant women and general population (e.g. PCBs, mercury); assessment of risks and benefits of different alternative fuels for sound energy policy development (e.g. oxygenated gasoline, biodiesel); and estimation of health risks associated with pesticide residues in food. The estimated risk is a function of exposure and toxicity. The regulatory risk assessment follows a four-step paradigm using qualitative and/or quantitative approaches. In quantitative risk assessment using either deterministic or probabilistic approaches, the risk estimates pertaining to an exposure scenario is particularly useful when comparing a number of exposure or risk reduction measures among one another as an optimization protocol to determine the best economically viable option for protection of public health and the environment. The four steps of risk assessment are i) hazard identification; ii) toxicity (or dose-response) assessment; iii) exposure assessment; and iv) risk characterization, which are described below in detail. The emphasis is given in documenting the resources necessary to successfully perform each step.
- In the hazard identification step, a scientific weight of evidence analysis is performed to determine whether a particular substance or chemical is or is not causally linked to any particular health effect at environmentally relevant concentrations. Hazard identification is performed to determine whether, and to what degree, toxic effects in one setting will occur in other settings. The evidence comes from human but also animal studies.
- Toxicity or dose-response assessment takes the toxicity data gathered in the hazard identification step from animal studies and exposed human population studies and describes the quantitative relationship between the amount of exposure to a chemical (or dose) and the extent of toxic injury or disease (or response). Generally, as the dose of a chemical increases, the toxic response increases either in the severity of the injury or in the incidence of response in the affected population.
- The magnitude of exposure is determined by measuring or estimating the amount of an agent to which humans are exposed (i.e. exposure concentration) and the magnitude of dose (or intake) is estimated by taking the magnitude, frequency, duration, and route of exposure into account. Exposure assessments may consider past, present, and future exposures.
- In the last step, a hazard quotient (HQ) as an indicator of risks associated with health effects other than cancer and excess cancer risk as the incremental probability of an exposed person developing cancer over a lifetime, are calculated by integrating toxicity and exposure information.
The improvement in the scientific quality and validity of health risk estimates depends on advancements in our understanding of human exposure to, and toxic effects associated with, chemicals present in environmental and occupational settings. Risk assessments are important for informed regulatory decision-making in environmental sustainability and to ensure that costs associated with different technological alternatives are scientifically justified and protest public health. Risk assessment helps federal agencies and risk management decision makers arrive at informed decisions about actions to take to protect human health from environmental hazards. Although significant uncertainties remain, this risk assessment methodology has been extensively peer-reviewed, is widely used and understood by the scientific community, and continues to expand and evolve as scientific knowledge advances.
Risk management (Figure below) is distinct from risk assessment, and involves the integration of risk assessment with other considerations, such as economic, social, or legal concerns, to reach regulatory decisions regarding the need for and practicability of implementing various risk reduction activities.
Finally, risk communication consists of the formal and informal processes of communication among various parties who are potentially at risk from or are otherwise interested in the threatening agent/action. It matters a great deal how a given risk is communicated and perceived: do we have a measure of control, or are we subject to powerful unengaged or arbitrary forces?
Toxic Substances Control Act (TSCA)
Information on all chemical substances and the control of any of these substances which may have an unreasonable health risk has been granted to the EPA through the Toxic Substances Control Act (1976). The manufacturer or the importer of a new chemical must provide information on the identity and hazard, use, production volume and disposal characteristics of the chemical to the EPA. Toxicological tests and unpublished health and safety studies on listed chemicals may be required by the EPA. The EPA may approve, prohibit, or limit the manufacture and sale of the listed chemicals, or may require special labeling. Since some chemical substances such as pesticides, tobacco products, nuclear materials, pharmaceuticals and cosmetics substances are regulated under other acts, they are exempted from TSCA regulations.
The production and distribution of polychlorinated biphenyls (PCBs) are prohibited through TSCA. PCBs are synthetic organic compounds that were manufactured to be used as electrical transformer oil; exposure to PCBs increases the risk of cancer, and may affect the reproductive and nervous systems. The EPA enforces the handling and disposal of PCBs based on established regulations on PCBs, in addition to management of PCBs found at hazardous waste sites. After the amendments of 1986 and 1990, TSCA through the Asbestos Hazard Emergency Response Act requires that all public and commercial buildings identify, control and mitigate the asbestos hazard in these buildings.
Furthermore, the TSCA provides EPA with authority to require reporting, record-keeping and testing requirements, and restrictions relating to chemical substances and/or mixtures. Certain substances are generally excluded from TSCA, including, among others, food, drugs, cosmetics and pesticides.
Section 8 (b) of the Toxic Substances Control Act (TSCA) requires EPA to compile, keep current and publish a list of each chemical substance that is manufactured or processed, including imports, in the United States for uses under TSCA. Also called the “TSCA Inventory” or simply “the Inventory,” it plays a central role in the regulation of most industrial chemicals in the United States.
The initial reporting period by manufacturers, processors and importers was January to May of 1978 for chemical substances that had been in commerce since January of 1975. The Inventory was initially published in 1979, and a second version, containing about 62,000 chemical substances, was published in 1982. The TSCA Inventory has continued to grow since then, and now lists more than 86,000 chemicals.
TSCA defines a “chemical substance” as any organic or inorganic substance of a particular molecular identity, including any combination of these substances occurring in whole or in part as a result of a chemical reaction or occurring in nature, and any element or uncombined radical.
Chemicals substances on the Inventory include:
- Organics;
- Inorganics;
- Polymers; and
- Chemical substances of unknown or variable composition, complex reaction products, and biological materials (UVCBs).
Chemical substances not on the Inventory are those with uses not regulated under TSCA. The use of these chemical substances is governed by other U.S. statutes on, for example:
- Pesticides,
- Foods and food additives,
- Drugs,
- Cosmetics,
- Tobacco and tobacco products,
- Nuclear materials, or
- Munitions.
For purposes of regulation under TSCA, if a chemical is on the Inventory, the substance is considered an “existing” chemical substance in U.S. commerce. Any chemical that is not on the Inventory is considered a “new chemical substance.”
In addition to defining whether a specific substance is “new” or “existing,” the Inventory also contains “flags” for those existing chemical substances that are subject to manufacturing or use restrictions.
Determining if a chemical is on the Inventory is a critical step before beginning to manufacture (which includes importing) a chemical substance. Section 5 of TSCA requires anyone who plans to manufacture a new chemical substance for a non-exempt commercial purpose to provide EPA with a Premanufacture Notice (PMN) at least 90 days before initiating the activity.
TSCA addresses the production, importation, use, and disposal of specific chemicals including polychlorinated biphenyls (PCBs), asbestos, radon and lead-based paint.
https://www.epa.gov/laws-regulations/summary-toxic-substances-control-act
Regulatory and Guidance Information by Topic: Toxic Substances
U.S. Environmental Protection Agency (EPA)
Under a broad range of federal statutes, EPA gathers health, safety and exposure data; requires necessary testing; and controls human and environmental exposures for numerous chemical substances and mixtures. EPA regulates the production and distribution of commercial and industrial chemicals, in order to ensure that chemicals for sale and use in the United States do not harm human health or the environment.
Food and Drug Administration (FDA)
The FDA helps to safeguard the food supply by evaluating the use of chemicals as food ingredients and substances that come into contact with food, such as through food packaging, storage or other handling to ensure these uses are safe. The FDA also monitors the food supply for chemical contaminants and takes action when we find that the level of a contaminant causes a food to be unsafe.
- Read more from the US Food and Drug administration (FDA) website about Food Chemical Safety – https://www.fda.gov/food/food-ingredients-packaging/food-chemical-safety
REACH Regulation – European Union Law
The REACH Regulation (EC 1907/2006) entered into force in 2007 and has since evolved to reflect the advancement of knowledge regarding various chemicals and their properties.
The Regulation on the registration, evaluation, authorisation and restriction of chemicals (REACH) is the main EU law to protect human health and the environment from the risks that can be posed by chemicals. This is done by better and earlier identification of the intrinsic properties of chemical substances and by taking measures, such as phasing out or restricting substances of very high concern. REACH also aims to enhance innovation and the competitiveness of the EU chemicals industry.
Under REACH, consumers have the right to know whether the products they buy contain harmful chemicals. These substances are found in everyday products, and they have been linked to serious and often irreversible effects on health or the environment.
REACH places responsibility on industry to manage the risks from chemicals and to provide safety information on the substances. To that end, manufacturers and importers are required to gather information on the properties of their chemical substances and to register that information in a central database in the European Chemicals Agency (ECHA). The Agency is the central point in the REACH system: it manages the databases necessary to operate the system, coordinates the in-depth evaluation of the information provided on chemicals and runs a public database where consumers and professionals can find hazard information.
The REACH Regulation aims to:
- ensure a high level of protection of human health and the environment against harmful substances
- assess the safety of chemical substances in use in the EU
- promote innovation and competitiveness
- promote alternative (non-animal) methods for the assessment of the hazards of substances
For more information visit https://environment.ec.europa.eu/topics/chemicals/reach-regulation_en#related–links
Comprehensive Environmental Response, Composition, and Liability Act (CERCLA)
The CERCLA (1980) also known as ‘Superfund” aims to provide for liability, compensation and the cleanup of inactive or abandoned hazardous waste disposal sites, and for emergency response to releases of hazardous materials into the environment. CERCLA gives the EPA the power and the funding to clean up abandoned hazardous waste sites and to respond to emergencies related to hazardous waste releases. The Superfund Amendments and Reauthorization Act (SARA) of 1986 solidified many of the provisions of CERCLA such as increasing the authority of the EPA to respond to remediation of hazardous waste sites with a faster startup for cleanup of contaminated sites, and greatly increased the available trust fund for cleanup.
The EPA uses the National Priority List (NPL) to identify contaminated sites that present a risk to public health or the environment and that may be eligible for Superfund money. A numeric ranking system known as the Hazard Ranking System (HRS) has been established to determine the eligibility of contaminated sites for Superfund
money, where sites with high HRS scores are most likely to be added to the NPL. The National Contingency Plan (NCP) provides guidance for the initial assessment and the HRS ranking of contaminated sites. After the initial assessment of a contaminated site, a remedial investigation is carried out where the NCP provides for a detailed
evaluation of the risks associated with that site. A remedial investigation results in a work plan, which leads to the selection of an appropriate remedy referred to as a feasibility study. The feasibility study assesses several remedial alternatives, resulting in Record of Decision (ROD) as the basis for the design of the selected alternative. The
degree of cleanup is specified by the NCP in accordance with several criteria such as the degree of hazard to the public health and the environment, where the degree of cleanup varies for different contaminated sites.
Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA)
Insecticides, fungicides and rodenticides are compounds that are employed to control or eliminate pest populations (pesticides). The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) of 1972 with several subsequent amendments set guidelines for the use of pesticides in the United States. All manufacturers or importers must
register their pesticide products with the EPA, where registration is allowed for a pesticide whose application does not have unreasonable adverse effects on the environment. Industries such as the agricultural sector employ pesticides to control vermin and other pests in industrial processes and in the workplace.
Occupational Safety and Health Act (OSHA)
The Occupational Safety and Hazard Act (OSHA) of 1970 and its amendment of 1990 aim to ensure safe and healthful working conditions for workers through enforcement of standards developed under OSHA, and to provide for research, training and education in the field of occupational safety and health. The standards for occupational health and safety are established by the Occupational Safety and Health Administration and its state partners, which are enforced through inspections of industry and providing guidance on better operating practices. The National Institute for Occupational Safety and Health (NIOSH) was established to recommend occupational safety and health standards based on extensive scientific testing, which are afterwards enforced by OSHA. Those industries which have followed OSHA standards have experienced a decline in overall injury and illness rates, where the costs due to worker injuries, illnesses and compensation associated with occupational safety are a major loss for industry. The OSHA standards for worker health and safety are recommended to be used in conjunction with various industrial pollution prevention programs.
Case Study – The Love Canal Disaster
One of the most famous and important examples of groundwater pollution in the U.S. is the Love Canal tragedy in Niagara Falls, New York. It is important because the pollution disaster at Love Canal, along with similar pollution calamities at that time (Times Beach, Missouri and Valley of Drums, Kentucky), helped to create Superfund, a federal program instituted in 1980 and designed to identify and clean up the worst of the hazardous chemical waste sites in the U.S.
Love Canal is a neighborhood in Niagara Falls named after a large ditch (approximately 15 m wide, 3–12 m deep, and 1600 m long) that was dug in the 1890s for hydroelectric power. The ditch was abandoned before it actually generated any power and went mostly unused for decades, except for swimming by local residents. In the 1920s Niagara Falls began dumping urban waste into Love Canal, and in the 1940s the U.S. Army dumped waste from World War II there, including waste from the frantic effort to build a nuclear bomb. Hooker Chemical purchased the land in 1942 and lined it with clay. Then, the company put into Love Canal an estimated 21,000 tons of hazardous chemical waste, including the carcinogens benzene, dioxin, and PCBs in large metal barrels and covered them with more clay. In 1953, Hooker sold the land to the Niagara Falls school board for $1, and included a clause in the sales contract that both described the land use (filled with chemical waste) and absolved them from any future damage claims from the buried waste. The school board promptly built a public school on the site and sold the surrounding land for a housing project that built 200 or so homes along the canal banks and another 1,000 in the neighborhood (see Figure below). During construction, the canal’s clay cap and walls were breached, damaging some of the metal barrels.
Eventually, the chemical waste seeped into people’s basements, and the metal barrels worked their way to the surface. Trees and gardens began to die; bicycle tires and the rubber soles of children’s shoes disintegrated in noxious puddles. From the 1950s to the late 1970s, residents repeatedly complained of strange odors and substances that surfaced in their yards. City officials investigated the area, but did not act to solve the problem. Local residents allegedly experienced major health problems including high rates of miscarriages, birth defects, and chromosome damage, but studies by the New York State Health Department disputed that. Finally, in 1978 President Carter declared a state of emergency at Love Canal, making it the first human-caused environmental problem to be designated that way. The Love Canal incident became a symbol of improperly stored chemical waste. Clean up of Love Canal, which was funded by Superfund and completely finished in 2004, involved removing contaminated soil, installing drainage pipes to capture contaminated groundwater for treatment, and covering it with clay and plastic. In 1995, Occidental Chemical (the modern name for Hooker Chemical) paid $102 million to Superfund for cleanup and $27 million to Federal Emergency Management Association for the relocation of more than 1,000 families. New York State paid $98 million to EPA and the US government paid $8 million for pollution by the Army. The total clean up cost was estimated to be $275 million.
The Love Canal tragedy helped to create Superfund, which has analyzed tens of thousands of hazardous waste sites in the U.S. and cleaned up hundreds of the worst ones. Nevertheless, over 1,000 major hazardous waste sites with a significant risk to human health or the environment are still in the process of being cleaned.
Biomagnification of Toxins
- Some toxicants can be excreted or metabolized, but fat-soluble toxicants (e.g. heavy metals) are stored in fatty tissues
- Bioaccumulation: toxicants build up in animal tissues
- Biomagnification: toxicants concentrate in top predators
- The result of biomagnifications include:
- Near extinction of peregrine falcons, bald eagles, and brown pelicans
- High PCB levels in polar bears
- Mercury in humans from fish consumption (mercury is released into the environment from various sources e.g. from mines, burning of fossil fuels)
- Figure on the right shows bioaccumulation of PCBs and mercury
- PCB or Polychlorinated biphenyls is used in coolants, paints, cements, PVC plastic etc.
Chemicals are an unavoidable part of modern day life for people living in many parts of the world. The problem is that many nations use the innocent until proven guilty principle when it comes to allowing a new chemical to be sold to the public as paints, cosmetics, pesticides, insecticides, plastics, furnishings, electronics etc.
- This means that most of the chemicals we use today have not been tested for toxicity to humans and other living things.
- The threat of lawsuits and scandal will prevent manufacturers from selling chemicals that have immediate toxic effects (acute exposure) (e.g. if you became very ill after painting your house)
- But nothing stops them from selling chemicals that have less obvious long-term toxicity (chronic exposure) because it would be hard to trace this type of toxicity back it its sources. (e.g. if the paint in your house contains lead and it slowly poisons you so that after 20 years you suffer from liver failure, it is not obvious to you that your illness was caused by the paint)
- Therefore it is important to educate ourselves about these environmental hazards and take steps to minimize our exposure and risk.
Summary
Environmental health is concerned with preventing disease, death and disability by reducing exposure to adverse environmental conditions and promoting behavioral change. It focuses on the direct and indirect causes of diseases and injuries, and taps resources inside and outside the health care system to help improve health outcomes. Environmental health risks can be grouped into two broad categories. Traditional hazards related to poverty and lack of development affect developing countries and poor people most. Modern hazards, caused by development that lacks environmental safeguards, such as urban (outdoor) air pollution and exposure to agro-industrial chemicals and waste, prevail in industrialized countries, where exposure to traditional hazards is low. Each year contaminated water and poor sanitation contribute to 5.4 billion cases of diarrhea worldwide and 1.6 million deaths, mostly among children under the age of five. Indoor air pollution—a much less publicized source of poor health—is responsible for more than 1.6 million deaths per year and for 2.7 percent of global burden of disease. Emerging and reemerging diseases have been defined as infectious diseases of humans whose occurrence during the past two decades has substantially increased or threatens to increase in the near future relative to populations affected, geographic distribution, or magnitude of impacts. Antibiotic resistance is a global problem. New forms of antibiotic resistance can cross international boundaries and spread between continents. Environmental toxicology is the scientific study of the health effects associated with exposure to toxic chemicals and systems occurring in the natural, work, and living environments; the management of environmental toxins and toxicity; and the development of protections for humans, animals, and plants. Environmental contaminants are chemicals found in the environment in amounts higher than what would be there naturally. We can be exposed to these contaminants from a variety of residential, commercial, and industrial sources.
Attributions
This chapter is composed of text taken from the following sources:
Libre Texts Engineering. Environmental Engineering is shared under a CC BY-NC Links to an external site.license and was authored, remixed, and/or curated by LibreTexts.
https://eng.libretexts.org/Bookshelves/Environmental_Engineering_(Sustainability_and_Conservation)/Book%3A_Essentials_of_Environmental_Science_(CK-12)/08%3A_Untitled_Chapter_8/8.03%3A_New_PageLinks to an external site.
Love Canal Case Study – A Comprehensive Foundation. Book: Sustainability – A Comprehensive Foundation (Cabezas)Links to an external site. is shared under a CC BY Links to an external site.license and was authored, remixed, and/or curated by Heriberto CabezasLinks to an external site. (GALILEO Open Learning MaterialsLinks to an external site.) .
Introduction to Environmental Science CK-12 Chapter 11 licensed under CK-12. Created by: Michelle R. © CK-12 Foundation 2023. https://www.ck12.org/user:bwvzdgfibguzn2vkdubnbwfpbc5jb20./book/introduction-to-environmental-science/
Sustainability – A Comprehensive Foundation (Cabezas) is shared under a CC BY license and was authored, remixed, and/or curated by Heriberto Cabezas (GALILEO Open Learning Materials) .
European Commission REACH Regulation. https://environment.ec.europa.eu/topics/chemicals/reach-regulation_en#related–links
References for PFAS
Federal Government Resources
- U.S. Environmental Protection Agency (EPA)
- Agency for Toxic Substances and Disease Registry (ATSDR)
- National Institutes of Health (NIH)
- Food and Drug Administration (FDA)
- United States Department of Defense (DOD)
- United States Navy
- United States Air Force, Civil Engineering Center
-
Our Current Understanding of the Human Health and Environmental Risks of PFAS
- https://www.epa.gov/pfas/our-current-understanding-human-health-and-environmental-risks-pfas