Pesticide Risk

For the discussion of pesticides, environmental and human health, Risk can be defined as:

The chance (i.e., potential) of harmful effects to human health or to ecological systems resulting from exposure to an environmental stressor. Environmental stressors is a broad term referring to any substance or lack of substance (e.g., dissolved oxygen in a pond) that can potential knock an ecosystem out of balance. Pesticides act as potential environmental stressors because of their inherent properties and intended uses. If the hazard (relative toxicity of a chemical compound) is high and exposure (the duration an organism is in contact with a hazard) is high, then the potential effects are also high. If something is very hazardous, but little to no exposure occurs, then the potential effects are low. Lastly, if a compound is moderately hazardous, but long-term exposure occurs, effects may also be high then as well.

Risk = Potential Exposure × Potential Hazard


Risk Assessment Paradigm

By their very nature, most pesticides create some probability (or potential) of adverse impacts on non-target species because they are designed to kill or otherwise adversely affect living organisms considered to be nuisance species. In order to determine if a pesticide poses an unacceptable risk (i.e., the environmental or human health risk outweigh the societal and economic benefits)3 the EPA’s Office of Pesticide Programs (OPP) completes a risk analysis for each registered pesticide that involves risk assessment, risk evaluation, and risk management. Risk communication to the public must also occur once the EPA reaches a registration decision for a pesticide.

The technical components of risk analysis occurs during the risk assessment phase whereby technical information is established regarding acceptable levels of risk for an individual, group, society, and the environment.10 The risk evaluation is considered a component of risk assessment in which judgments are made about the significance and acceptability of risk.10 The final stage of the risk analysis process is risk management, whereby a decision is made as to what action should be taken based on the consideration of the risk assessment information and other non-technical information for each pesticide.4

Flow diagram of the risk analysis for decision-making for pesticides from the technical to non-technical aspects of the process:

Risk Analysis Flow Diagram

The role of science in risk assessment is to ensure that the actions implemented by risk managers achieve the goals and objectives defined by our society.11 Several factors ultimately influence the final determination during the risk management process including economic factors (i.e., costs of risks and/or mitigation), laws and legal decisions, socioeconomic factors, technological factors (i.e., the feasibility of risk management), political factors (i.e., local, state, and federal levels), and lastly public values and attitudes towards perceived risk.12 Perceived risk and actual risk may be very different in some cases. This is where risk communication comes into play ( If the public is misinformed about potential adverse effects of a compound then perceived risk can be very different from actual risks that compound may pose. The risk communicator must then try to properly inform the public at large. Conversely, when a compound causes a crisis situation, the risk communicator must reassure the public that everyone is working together to get through the crisis. Often, information that is presented to the public at large is from news media - not from the EPA or company manufacturing a product leading to controversy and sometimes litigation. Therefore, sometimes information may be skewed to promote agendas. If the public is pushing for more information to be gathered or for a certain pesticide to be phased out, the EPA will frequently form a Scientific Advisory Panel (SAP) made of various stakeholders and experts within the field. Then a final decision about the compound will be made by the SAP panel. modern risk communication

Societal Risk vs. Benefit:

At what point does the use of a pesticide exceed societal benefit? This is a question is posed by the EPA and pesticide manufacturers must ask This question can be re-phrased into when are risks too high and benefits too low, and how long will it take for benefit to occur? Often, there is no concise answer to this question and compounds fall into a moderate category, whereby the question is then often answered in an economical way using a Risk-Cost-Benefit-Analysis (RCBA) and societal input about the compound. RCBA answers the question by estimating Net Present Value (NPV) through a series of calculations looking at the potential benefit of a product (profit from a product), the potential cost associated with the risk and mitigation efforts if needed over a period of time.

risk analogy

The relative cumulative ranking system values were obtained during the risk assessment process (middle row of proceeding diagram). It is the goal of to maintain consistency with values used during regulatory decision-making to maintain consistency with the present risk framework. This will allow residents to make informed decisions about what pesticide (if any) is best to use depending on the scenario, and if in some cases, an alternative treatment option is the safest option. The toolbox ultimately allows you to use technical data from the risk assessment process in order for you to also make your own informed decisions.

Diagram illustrating the interface between research, risk assessment, and risk management and the components of each that plays a role in determining how the EPA makes a final decision about a pesticide (Pautsenbach, 2010, NRC, 2009).

Risk Assessment Paradigm

Simple Risk Paradigm

The EPA implements the National Research Council’s (NRC) four-step process for risk assessment:

  1. Hazard Identification measures the toxicity of the pesticide
  2. Dose-Response Assessment measures the amount of a substance a organism could potentially be exposed to and is as important as how toxic the chemical might be
  3. Exposure Assessment analyzes the effects of different types of exposure (ingestion, inhalation) to a pesticide (focuses on human health risk)
  4. Risk Characterization combines the hazard, dose-response and exposure assessments to describe the overall risk from a pesticide.

US EPA's Ecological Risk Assessment Framework and Phases:

When conducting an ecological risk assessment (in diagram form below), before the hazard identification, dose-response assessments, and exposure assessments begin, much planning - and then problem formulation - must be completed. Once certain questions are devised, then the analysis phase begins and technical information is gathered through hazard identification, etc. For the Decision-Making Toolbox for pesticides, data gathered during the analysis phase is used to relatively rank the compounds covered. The final phase of ecological risk assessment is risk characterization, whereby risk estimations and descriptions are determined. With risk estimation, there are assumptions built into the process and uncertainties that remains. Given the multitude of compounds on the market, ideally implementation of a high through-put bioassay that minimizes the number of test subjects and maximizes the data output would act as an initial screening process, thereby allowing reallocation of resources to compounds that need further data collected. This would both decrease overall cost and time of assessing risk while simultaneously increasing the attention given to potentially higher risk compounds.

assessment framework

All figures above courtesy of Dave Volz, Ph.D., Department of Environmental Health Sciences, University of South Carolina

Learn about a Brief History of US Pesticide Use