The dose makes the poison is the most basic principle of toxicology. The first chapter in every toxicology textbook discusses how the response to a poison depends on how much of the poison you are exposed to (often referred to as the “dose”). This principle assumes that chemicals act by overwhelming the body’s defenses at higher doses. It also assumes that at some lower dose, there is no harm or no effect.

But this basic principle may no longer hold true as what we know about exposures to toxic chemicals is changing. Some time ago, Linda Birnbaum, former director of the National Institute for Environmental Health Sciences, wrote an overview paper on the changing science in the field of environmental health. She wrote in this paper that the antiquated perception of how chemicals act is being replaced by a “better understanding of the actual characteristics of modern environmental chemicals.”

These characteristics include the timing and vulnerability of exposure, exposures to mixtures, effects at low doses, and genetic alterations called “epigenetics.” Birnbaum addressed each of these frontiers of toxicology and discussed how each affects our understanding of the link between the environment and public health.  

It’s clear now that the body’s response to toxic chemicals is complex and not as predictable as classic toxicology would lead us to believe. Chemicals such as bisphenol A (BPA) and dioxin cause adverse effects at low doses, not predictable by classic toxicology. No longer can you safely assume that at some low dose there is no harm. Birnbaum makes it clear that within traditional toxicity “… [testing] of effects at some high doses are no longer adequate to [determining] the full spectrum of response from a given chemical.” What’s more, the effects observed at low doses may be different than those observed at higher doses.

We also now know that there are critical “windows of exposure” during development that determine effects – the same exposure at different times can result in different effects. There are also enhanced periods of vulnerability during prenatal development that “program” the bodies’ physiology leading to diseases in later life. According to Birnbaum, this phenomenon has been demonstrated for hypertension, coronary heart disease, and neurological and cognitive development.

Another advance in our understanding of toxicology comes from the field of epigenetics, or the study of changes in DNA expression that are independent of the DNA sequence itself. We now know that exposures to chemicals can alter the normal triggering mechanism that turns genes on or off that determines a person’s observable traits, such as blue eyes or susceptibility to diabetes or other illnesses. Says Birnbaum, “[We’re] born with our genes, but epigenetic changes occur because of environmental influences during development and throughout life.”

These advances in toxicology raise many questions about the adequacy of traditional methods of assessing the impact of exposure to chemicals like BPA or dioxin, not to mention mixtures. Regulatory agencies have not integrated this new science into the methods they use to assess public health risks and it’s likely to take some time before traditional toxicologists accept this new thinking and integrate it into their methods for assessing public health risks. In the meantime, recognize that some of what public health officials are telling you is antiquated and no longer applicable to the world we live in.

It’s common to think that in science and technical information lies the answer to the many questions people ask about exposures to toxic chemicals. At CHEJ, we have not found this to be the case. While science and technical information is very important, by itself it cannot answer most of the questions people raise about exposure to toxic chemicals. People want answers and they want action to address the contamination in their community. Science and technical information can play a vital role in helping to achieve community goals, but identifying this role and learning how to use scientific and technical information is critical to the success of a local group. 

Many assume that if you hire the best scientists and engineers and make solid technical arguments, the government will do the right thing. It rarely works that way. It’s not because people who work for government don’t care, it’s just that the science is not there for government to justify acting. This is primarily because of the lack of scientific knowledge and understanding of how exposures to toxic chemicals lead to health outcomes in people. Scientists know little about the adverse health effects resulting from exposure to combinations of chemicals at low levels. As a result, when politicians and bureaucrats look for answers, the scientists usually don’t have them. 

At first glance, this may not make sense. We know so much about many toxic chemicals, like lead and dioxins, for example. But when it comes right down to it, we know very little about what happens to people when they are exposed to low level mixtures of toxic chemicals, even those that include lead and dioxins.

We can estimate risks and talk about the hazards associated with exposure, but we just don’t know much about the mechanisms of how chemicals damage the human body, especially in low level mixtures over long periods of time. This is because in most cases, there is very little information about what a person is exposed to, the concentration they are exposed to, and for how long. A person’s health conditions and prior exposures to toxic chemicals also play a role. In addition, there is no way to distinguish or fingerprint an exposure with a health outcome. 

Most scientists are reluctant to discuss how little is known about the link between health outcomes and exposures. Instead, the tendency is to discuss the “risks” of exposure which eventually leads to a debate over what’s an “acceptable” risk. This process hides the fact that scientists don’t know what happens to people who are exposed to low levels of a mixture of toxic chemicals. 

Because of this lack of scientific clarity, bureaucrats and politicians use “science” cloaked in uncertainty, not facts, to justify decisions which are based on the political and economic pressures they face. It is naïve to think that science and the many uncertainties resulting from exposures to toxic chemicals can serve as anything but a tool used by politicians and corporations to do what they want. 

In the face of these uncertainties, government sees as its main role and primary responsibility to maintain control of a situation and to assure the public that everything is fine, whether it is or not. The government cannot afford to say what it really knows about a situation, which often, is very little. If they did that, then the public would demand action that they could not scientifically justify taking. 

Despite these realities, there is a critically important role for science and information to play in addressing exposures to toxic chemicals. This role is to document the exposures and risks posed by these exposures and to support the arguments of activists and people exposed to toxic chemicals. The role of science and technical information is to be part of a larger strategic plan to help the community and the individuals who have been exposed to toxic chemicals achieve their goal, whether it’s to be relocated, or to achieve cleanup of a contaminated site. It’s important to recognize what science and technical information can tell you and what it can’t. 

Community leaders are constantly asking government officials and scientists to explain the risks of being exposed to toxic chemicals. The answers they get are typically all over the place. Often people hear that you don’t have to worry, that the risks from living near a toxic contamination problem is no different than smoking cigarettes, eating a peanut butter sandwich, or living in an urban area. Government and industry further argue that it has never been proven that the health of the people at Love Canal was damaged by the chemicals leaking from the landfill, that the dangers of dioxin are overstated, and that people become “hysterical” just because they have been exposed to toxic chemicals.

No question people are upset. But they’re not upset because they can’t understand complicated risk assessments or detailed toxicity information. They are upset because government and industry trivialize their concerns, because they can’t get good information on the toxicity of chemicals, and no one will give them an honest answer about potential health effects caused by exposure to toxic chemicals.

There is no question that toxic chemicals can cause adverse health effects. What’s not so clear is how chemicals cause adverse health effects in people. Part of the reason for this is that for most chemicals, there is not enough information on what happens to people when they are exposed while eating contaminated food, drinking polluted water, or breathing toxic air. A classic 1984 National Academy of Sciences report found that we had good information on only 8% of over 65,000 chemicals in use. Not much has changed since then.

While most of the information on toxicity of chemicals comes from animal studies, the workers who manufacture toxic chemicals are the greatest source of information on the toxicity of chemicals. From their experience, we found that dusty air causes lung cancer, benzene causes leukemia, radioactive paint, bone cancer, vinyl chloride, liver cancer, and certain pesticides, muscle weakness and paralysis.

In the community, an association between health problems and exposure has been harder to “prove”, but still many examples exist, especially among children who are highly susceptible to toxic chemicals. At Love Canal, children who were born and raised next to the canal had higher rates of birth defects; in Tucson, AZ, children whose parents drank water contaminated with trichloroethylene (TCE) were born with 2-1/2 times more heart defects than normal; and in Santa Clara County, CA, state health researchers found an “unequivocal excess” of miscarriages and birth defects in a San Jose neighborhood where trichloroethane (TCA) and other toxic chemicals were found in the drinking water.

Despite these and other findings, scientists still find it extremely difficult to tell exactly what health effects will occur following exposure to toxic chemicals. There are a number of reasons for this. First, many factors determine what happens when a person is exposed to chemicals, including how an individual body responds to exposure (this varies widely from person to person), how long exposures occur, how many chemicals you’re exposed to and their toxicity. Without knowing these variables, it’s difficult to predict what will happen when a person is exposed (in most instances, most of these factors are unknown).

A second factor is that many symptoms or diseases are not specific to a particular chemical. In most instances, there can be many causes of the symptoms that people are having. And since few physicians have any experience with exposures to toxic chemicals, rarely do they look at chemicals as a possible explanation. For example, many physicians will diagnose a person who is fatigued, moody and without appetite as “depressed”, likely to have a problem at home or at work. Seldom is exposure to toxic chemicals considered, even if it’s raised by the patient.

Another problem is determining what the “normal” rate of illness or disease is in a community. Scientists simply can’t decide amongst themselves what is normal, in large part because of the many uncertainties we’ve already discussed.

As a result, interpretation of the risks posed by exposures to toxic chemicals is largely a matter of opinion, not fact. Government and industry may criticize people for being “hysterical” or emotional when trying to explain health risks. But without clear information and explanations, people are pretty much out in the cold. Scientists need to be more honest about what is known and what’s not known about low level exposures to mixtures of chemicals. Once people have this information, they may not be fully satisfied, but at least they have a good sense of what’s known and what’s not. Then people are in a better position to decide what action they need to take.

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.