Chemicals Used on Land
What are the trends in chemicals used on land and their effects on human health and the environment?
Use and Disposition
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 in the environment and may bioaccumulate in the food chain (e.g., persistent, bioaccumulative, and toxic chemicals).
Chemicals are introduced into the environment through acts of nature (e.g., volcanoes, hurricanes), spills on land, emissions to air, and discharges to water. For example, 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).
- 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.
- Through deliberate application of chemicals to the land 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 United States is important to better understand the potential for those chemicals to affect human health and the environment.
- 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 (chronic), 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.2
- 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.
While chemicals in soil or on plants may be an initial pathway into the environment, it is the movement and concentration of chemicals through the food chain that are often of greatest concern, as well as exposures from other media such as contaminated water or air.
The indicators provide information on a relatively small universe of toxic chemicals and only limited information on the potential exposures humans may experience as a consequence of chemical use.
For example, the Pesticide Residues in Food indicator provides information on one aspect of the potential for human exposure from pesticides (dietary intake from the commercial food supply), but does not provide a complete picture of all the ways in which humans can be exposed to pesticides, which include contaminated drinking water, pesticide drift, and dermal contact.
With regard to the two pesticide-related indicators, no existing reporting system currently provides information on the volume, distribution, and extent of pesticide use in the United States. Estimates for these indicators were developed based on information available through a variety of reports from multiple governmental and non-governmental entities on pesticide sales, crop profiles, and expert surveys.
 U.S. Department of Health and Human Services. 2005. Report on carcinogens. Eleventh edition. Washington, DC: Public Health Service, National Toxicology Program.
 U.S. Environmental Protection Agency. 2010. Nutrients in estuaries: A summary report of the National Estuarine Experts Workgroup 2005-2007. Washington, DC.