Endocrine Disrupting Chemicals and Environmental Toxicology
Environmental toxicology is a multidisciplinary field of science concerned with the study of the harmful effects of various chemical, biological, and physical agents on living organisms. Environmental toxicologists study the effects of toxicants at various concentrations in labs and try to understand the potential for the bioaccumulation in food webs, including our own food supply. Harmful effects of chemicals like DDT and pollutants, insecticides, pesticides, and fertilizers have been found to affect organisms and their communities by reducing species diversity and abundance. These changes in population dynamics then affect the ecosystem by reducing its productivity and stability.
The Growth of Environmental Toxicology and the EPA
The growth of environmental toxicology as a distinct field began with Rachel Carson in 1962 with the publication of her book Silent Spring, which covered the effects of uncontrolled pesticide use. The book was based on reports by Lucille Farrier Stickel on the ecological effects of the pesticide DDT. The increase in understanding of environmental impacts of pollutants, coupled with the 1969 Cuyahoga River Fire in Cleveland, caused national uproar which led the US Congress enacting the National Environmental Policy Act of 1969 to help protect the public from environmental pollutants. The EPA was created the following year and was tasked with the responsibility of maintaining and enforcing national standards created by various environmental policy laws such as the Clean Air Act, the Clean Water Act, and Toxic Substances Control Act. In addition to federal regulations, each state also has separate regulations and agencies designed to help regulate and enforce environmental policy.
Endocrine Disruptor Screening
A growing section of research in environmental toxicology is on chemicals that carry the potential to greatly impact the endocrine system. Collectively referred to as endocrine-disrupting chemicals (EDCs), these compounds include bisphenols, phthalates, parabens, and others share some physicochemical properties with natural hormonal ligands. This allows them to bind to nuclear receptors such as the estrogen, androgen, and thyroid receptors to either activate or inhibit their action. Depending on the type and outcome, EDCs can impact puberty, immune function, stress, weight, bone health, and more in humans and wildlife.
Because of this, the EPA created the Endocrine Disruptor Screening Program (EDSP), which screens pesticides, chemicals, and environmental contaminants for their potential effect on estrogen, androgen, and thyroid receptors. The EDSP subjects’ compounds to two tiers of testing, to evaluate if they are EDCs. Tier 1 screens chemicals that have the potential to interact with the endocrine system through in vitro assays and in vivo animal models, and Tier 2 involves more in-depth testing of chemicals flagged in Tier 1.
Research on EDCs continues to grow, and the EPA and environmental toxicologist are looking to understand where EDCs get into the environment and how to prevent ecological events, such as those seen with DDT. Landfills, solid waste sites, wastewater, biosolids, and animal feeding operations are assessed and studied for these purposes. Through close examination of suspected EDCs, as well as potential environmental indicators for EDC interaction, we can better understand the ability that these compounds have and how they may impact us and the environment.