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
Effects
ROE Indicators

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), or through human activities such as:

Through deliberate application of chemicals to the land in agricultural production to increase crop yields and control fungi, weeds, insects, and other pests.
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.

Tracking trends in chemicals used on land in the United States is important to better understand the potential for those chemicals to affect human health and the environment.

Effects

Some chemicals pose little risk to human health or environmental condition, while others, such as known carcinogens,¹ pose serious risks when sufficient exposure occurs.

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.

The risks associated with chemicals depend 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.

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.

ROE Indicators

The ROE presents four indicators to describe trends in chemicals used on land: Agricultural Fertilizer, Pesticide Exposure in Food Pesticide Incidents, and Pesticide Residues in Food. Indicator-specific limitations are discussed in the descriptions of these indicators.

With regard to the pesticide incidents and residues in food 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. The pesticide exposure in food indicator represents an exposure index that shows relative changes in exposure to two selected pesticide groups in children compared to a base year and takes into account the relative toxicities of these pesticides.

References

^[1] U.S. Department of Health and Human Services. 2021. Report on carcinogens, Fifteenth edition. Research Triangle Park, NC: Public Health Service, National Toxicology Program.

^[2] U.S. Environmental Protection Agency. 2022. Nutrient Pollution.