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Chemicals
Land Chapter
- Introduction
- Overview
- List of Questions
- Introduction
- Overview
- Discussion
- HD National Trend
- List of Indicators
- References
Chemicals
- Maricruz MaGowan
Office of Environmental Information
roe@epa.gov
Chapters
What are the trends in chemicals used on the land and their effects on human health and the environment?(Chemicals to include toxic substances, pesticides, fertilizers, etc.)
Many chemicals and chemical products are considered essential to modern life because of the benefits they provide. Some break down quickly, while others persist for long periods of time in the environment and may bioaccumulate in the food chain (e.g., persistent, bioaccumulative, and toxic chemicals [PBTs]).
Introduction of chemicals into the environment occurs through acts of nature (e.g., volcanoes, hurricanes), spills on land, emissions to air, and discharges to water. Chemicals can be released through large- and small-scale industrial and manufacturing activity, in the production and storage of food and consumer products, in efforts to manage or eradicate insect-borne diseases (e.g., West Nile virus, Lyme disease), or through personal actions such as the use and improper disposal of household products (e.g., lawn care materials, pharmaceuticals, cleaning products, batteries, paint, automotive products) or wastes. Deliberate application of chemicals to the land is widespread in agricultural production to increase crop yields and control fungi, weeds, insects, and other pests.
Tracking trends in the use and disposition of chemicals in the U.S. is important to better understand the potential for those chemicals to affect human health and the environment. Many chemicals pose little known hazard to human health or environmental condition, while others pose risk. Many chemicals are recognized as carcinogens.22 The effects of chemicals on human health and other ecological receptors through environmental exposure can be acute and very toxic, subtle and cumulative over time, or nonexistent. Chemicals can be of concern because of their pervasiveness, potential to accumulate, possibilities of interaction, and often long-term unknown effects on people and the environment (e.g., cancer, mercury in fish). Humans and wildlife may be affected by certain chemicals through direct exposure, including accidental ingestion or inhalation, accumulation and uptake through the food chain, or dermal contact.
Similarly, ecosystems and environmental processes may be compromised or contaminated through the migration and accumulation of chemicals (e.g., via uptake by plants, fugitive dust and volatilization, and migration to water supplies). For example, excessive nutrient loading from over-fertilization can result in runoff that causes adverse effects in aquatic ecosystems.23 Widespread exposure to, or misuse of, pesticides can harm non-targeted plants and animals (including humans), as well as lead to development of pesticide-resistant pest species.
It is difficult to make generalizations about the effects of chemicals and chemical usage, not only because there are thousands of chemicals, but also because individual chemicals have unique ways of being absorbed and handled by living organisms. The risks associated with chemicals are dependent on many factors, including exposure and toxicity—which can be acute or chronic, and can occur at multiple stages of the chemical life cycle. Different stages in the life cycle of chemicals, such as manufacturing, transport, application or use, runoff, or accumulation, pose different hazards to humans and the environment.