Factsheet on Ecological Risk Assessment for Pesticides

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Key Terms

  • Ecological Risk Assessment: Evaluation of the likelihood that a pesticide will harm wildlife or the environment.
  • Ecosystem: The complex of a community of organisms and its environment functioning as an ecological unit.
  • Environmental Fate: What happens to the pesticide in soil, water, and air after being released into the environment.
  • Non-target species: Organisms other than that which the pesticide is intended to kill.
  • Target species: The organism the pesticide is intended to kill.
  • Toxicology: The harmful effects of a poison on living systems.

EPA conducts ecological risk assessments to determine what risks are posed by a pesticide and whether changes to the use or proposed use are necessary to protect the environment.

Many plant and wildlife species can be found near or in cities, agricultural fields, and recreational areas. Before allowing a pesticide product to be sold on the market, we ensure that the pesticide will not pose any unreasonable risks to wildlife and the environment. We do this by evaluating data submitted in support of registration regarding the potential hazard that a pesticide may pose to non-target fish and wildlife species. The following are some answers to frequently asked questions about the way we evaluate ecological risk.

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What is An Ecological Risk Assessment?

In an ecological risk assessment, we evaluate the likelihood that exposure to one or more pesticides may cause harmful ecological effects. The effects can be direct (e.g., fish die from a pesticide entering waterways, or birds do not reproduce normally after ingesting contaminated fish), or indirect (a hawk becomes sick from eating a mouse dying from pesticide poisoning).

We determine the likelihood of harmful effects based on scientific measurements and on scientific judgement. Our risk assessments are prepared by scientists trained in wildlife ecology, population dynamics, physiology, and environmental chemistry. An ecological risk assessment employs the most current scientific methods to determine if a pesticide meets the requirements for registration and will not significantly harm wildlife.

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How Does The Process Work?

To propose a pesticide for registration in the United States, the manufacturer must conduct many scientific studies according to EPA's requirements. The manufacturer then submits the data to us, where we review it and determine the pesticide's potential to cause problems. In some cases, we may require additional data to resolve questions which arise during our initial evaluation. The final step is our decision to approve or deny registration.Ecological risk assessments are one of several tools we use to evaluate new pesticides and re-evaluate old ones. In April 1998, EPA established Guidelines for Ecological Risk Assessment that describe the risk evaluation process and present a methodology that EPA can use when investigating environmental problems. This ensures that our risk assessments are consistent throughout EPA.

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What Kind of Studies Does EPA Look At For Environmental Risks?

Ecological Data Requirements for Pesticide Registration

  • Wildlife and aquatic organisms: How the pesticide affects various animal species.
  • Plant protection:How the pesticide affects various plant species.
  • Environmental Fate: What happens to the pesticide in soil, water, and air after being released into the environment.
  • Non-target insect: How the pesticide affects insects other than the ones the pesticide is intended to kill.
  • Environmental fate: What happens to the pesticide in soil, water and air after being released into the environment.
  • Residue chemistry: How much pesticide remains after application over time. Helps determine how much pesticide is present in the environment over time.
  • Spray drift: How much the pesticide drifts off-site when sprayed from the air. Helps determine exposure of non-target organisms.

The studies we use in our ecological risk assessments define the chemical properties of the pesticide, how the pesticide behaves in the environment, and its impact on plants and animals not targeted by the pesticide.

Wildlife/Plant Toxicity

Toxicology studies are carried out on plants and animals that have been chosen for testing because they broadly represent non-target organisms (living things the pesticide is not intended to kill). The animals and plants are exposed to different amounts of pesticide to determine short- and long-term responses to varying concentrations. Some of the impacts we look at on animals are the short- and long-term effects of varying amounts of pesticide exposure to insects and other invertebrates, fish, and birds. For plants, we look at how poisonous the pesticide is to plants, how the pesticide affects a seed's ability to germinate and emerge, as well as how healthy and vigorous the plant grows up.

Toxicological testing and scientific measurements are conducted under strict guidelines and approved methods. Exacting standards are necessary for consistency in evaluations of pesticide safety and for comparisons among chemicals.

Environmental Fate

Other studies measure the interaction of pesticides with soils, air, sunlight, surface water, and ground water. Some of the basic questions that must be answered in these studies are: (1) How fast and by what means does the pesticide degrade? (2) What are the breakdown chemicals?(3) How much of the pesticide or its breakdown chemicals will travel from the application site, and where will they accumulate in the environment? These tests include how the pesticide breaks down in water, soil, and light; how easily it evaporates in air; and how quickly it travels through soil. EPA uses these tests to develop estimates of pesticide concentrations in the environment.

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Putting the Pieces Together

To evaluate a pesticide's environmental risks, we look at all the data together. The process of comparing toxicity information and the amount of the pesticide a given organism may be exposed to in the environment is called risk assessment.

A pesticide can be toxic at one exposure level, and have little or no effect at another. Thus, the risk assessor's job is to determine the relationship between possible exposures to a pesticide and the resulting harmful effects.

If the ecosystem will not be exposed to levels of a pesticide shown to cause problems, EPA concludes that the pesticide is not likely to harm plants or wildlife. On the other hand, if the ecosystem exposure levels are suspected or known to produce problems, we will then work to better understand the risks and reduce the risks to acceptable levels.

If the risk assessment indicates a high likelihood of hazard to wildlife, we may require additional testing, require that the pesticide be applied only by specially-trained people, or decide not to allow its use. Decisions on risk reduction measures are based on a consideration of both pesticide risks and benefits.

When we issue a registration for a pesticide, we make sure that we comply with all health and safety requirements, including that use according to label directions will not cause unreasonable harmful effects on wildlife or the environment.

Find the EPA Guidelines for Ecological Risk Assessment on EPA's website or from the National Technical Information Service (NTIS), telephone: (703) 487-4650; fax (703) 321-8547. Please provide the NTIS publication number (PB98-117849).

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More Information

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