Toxic Tuesdays

CHEJ highlights several toxic chemicals and the communities fighting to keep their citizens safe from harm.

Risk Assessments

It is difficult to interpret health risks when people are exposed to toxic chemicals. This is largely driven by the lack of information about what happens to people when they are exposed to toxic chemicals.  

In the face of this uncertainty, the government, primarily the USEPA, developed the process called “risk assessment” as the means for evaluating health risks. This approach calculates the probability that exposure to a single toxic chemical, considered in isolation, will result in a specific level of harm to people. And, if the calculated probability falls below a targeted risk level defined by the government as “acceptable” (say one cancer in 100,000 individuals exposed for a lifetime), then that exposure is considered acceptable.

Risk assessment was developed in the 1970s and soon became the “go to” approach for evaluating health risks resulting from exposure to toxic chemicals, whether setting cleanup standards at Superfund sites, regulating toxic air emissions or waste water discharges, or for determining safe levels of contaminants in food. But instead of protecting or even prioritizing public health, the use of risk assessment has resulted in our regulatory system allowing broad-scale contamination of the planet by defining “acceptable” levels of contamination and exposure to toxic chemicals.

The risk assessment process has improved over the years, but it still suffers many critical limitations that make it inadequate and inappropriate for assessing public health risks. These limitations begin with a primary focus on cancer, ignoring reproductive, nervous system, immune, and other noncancer effects. This narrow focus also fails to consider the likelihood of getting rashes, headaches and dizziness, breathing disorders, allergies, liver and kidney effects, etc.

Another major limitation is the consideration of exposure to only one chemical at a time. This approach ignores the multiple chemicals that people are realistically exposed to at a contaminated site, or from an industrial source, as well as from other sources that contribute to a person’s overall toxic body burden including drinking water, ambient air, and food sources. It also ignores the additive, cumulative, and synergistic effects that result from exposures that occur daily and over time from all sources combined.

There is also great uncertainty in what we know about the toxicity of most chemicals. We actually know very little about the toxic effects of most chemicals. We have good toxicity information on only about 8% of the more than 65,000 chemicals in use. Lastly, people vary greatly in genetic characteristics, age, sensitivity and pre-existing conditions that all influence how a person responds to exposures to toxic chemicals. And, we have no way to characterize or predict this response.

To address these limitations and shortcomings, Peter Montague published  a number of explicit warnings that should accompany every formal risk assessment. These warnings include the following:

  • Assessing the risks to a hypothetical “most exposed individual” has led to a world contaminated by the cumulative effects of millions of low-level discharges and small stresses.
  • Risk assessors should acknowledge that most people are routinely exposed to mixtures of chemicals (pharmaceuticals, food additives, pesticides, secondhand smoke, vehicle exhaust, disinfectants, cleaning agents, fine particle pollution, pollutants in drinking water, and releases from consumer products (among others).
  • Risk assessments can mislead, confuse and exclude the public, thereby diminishing democratic participation.
  • Risk assessments are not scientific in the sense that they often are not reproducible when different people assess the same risks. Conclusions can vary dramatically (by a factor of 1,000 or more), depending on who’s doing the assessment.   
  • The selection of data determines the conclusions. The selection and use of particular data should be explained and defended as should the exclusion of particular data.
  • Informed consent is ethically essential. For the past 50 years, the general public and environmental justice communities in particular, have been subject to chemical exposures and other stressors without their informed consent. They suffer the consequences with their health.

While these warnings are important and could help people read and use risk assessments in reduce the danger of misusing or misunderstanding the results of the risk assessment process, they don’t address a critical question posed by people exposed to toxic chemicals: How will my health, or the health of my children, family, or community, be affected?

Risk assessment cannot answer this question, no matter how well done or how much context is provided to help reduce misuse and misunderstanding. People exposed to toxic chemicals suffer for years as scientists do health studies, health assessments, data evaluations, and risk estimates. In the end, the risk assessment process typically shows that the levels of toxic chemicals people were exposed to are not likely (or some similar caveat) to cause any adverse health effects. 

No matter how well designed, risk assessments cannot answer this question. Instead, we need to think of another way to provide relief for people who suffer from toxic chemical exposures. 

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