One of the hardest things for a public health scientist to do is to link a specific health problem that a person is suffering from to a specific exposure to a toxic chemical(s). People who have been exposed to toxic chemicals, whether they lived at Love Canal, NY, Flint, MI or East Palestine, OH, want to know if their cancer, diabetes or other illness was caused by exposure to toxic chemicals. This is a reasonable question for people to ask, and it is one we hear all the time from people in the communities we work with. Unfortunately, the answer is not so clear. 

The problem is that scientists know very little about how and why the body responds to toxic chemicals the way it does. While we know a great deal about the mechanism of action for some chemicals such as dioxin and lead, we do not know what is going to happen to an individual who is exposed to 5 parts per trillion (ppt) of dioxin in their food. Or to a child who eats lead paint chips for 3 months. In some cases, scientists can predict what symptoms to expect, but it is rare that they can confidently link specific health outcomes to specific exposures even in obvious situations like the drinking water disaster in Flint, MI.

In fact, there are only two chemicals – asbestos and vinyl chloride – out of the more than 80,000 chemicals in use today, that scientists have been able to clearly link between exposure and specific health problems. In the case of asbestos, if you were exposed to asbestos in the shipping industry and develop a rare cancer of the outer lining of the lungs called mesothelioma, scientists are 99% confident (as close to certain as one can get) that the asbestos caused your lung cancer. In the case of vinyl chloride, if you were exposed to vinyl chloride in a PVC manufacturing plant and develop a rare cancer of the liver called angiosarcoma, scientists are 99% confident that the vinyl chloride caused your liver cancer. In both cases, it was an observant clinician who noticed that the people with these rare cancers all worked at the same place and had similar exposures.   

There are several factors that determine what happens when a person is exposed to chemicals. These factors include an individual’s susceptibility (this varies greatly from person to person), how long exposures occur, how many chemicals a person is exposed to, the concentration of these chemicals, and the toxicity of the chemicals. Add in the reality that people are often exposed to more than one chemical at a time and often repeatedly over time, then the certainty over what is known becomes significantly less. Even if you knew all these factors (which is rare), it is still almost impossible to predict what will happen when a person is exposed. We’ve touched on many of these factors in previous issues of Toxic Tuesday.

In addition, there is no way to fingerprint an exposure to tie it to a specific health outcome. And 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 few physicians have experience with exposure to toxic chemicals. Meaning they cannot distinguish whether the headache you are suffering from resulted from the chemicals you were exposed to or whether you had a hard day at work. Often this inexperience leads to blaming the victim for their situation rather than looking at chemicals as a possible explanation. Another problem is determining what the “normal” rate of illness or disease is in a community. Scientists simply cannot decide what is normal. This is in large part because of the many uncertainties already discussed.

Despite the many scientific uncertainties, linking cause and effect has become the standard to achieve before government will take action to address a pollution problem or protect a  community. Over the years, this has meant endless studies and years of research gathering data that has resulted in little or no action on the part of government to protect people and communities exposed to toxic chemicals. This has been the government’s approach since before Love Canal more than 40 years ago. This is what is happening now in East Palestine, OH. This is no longer reasonable nor acceptable.

It is time to acknowledge that scientists do not know very much about how or why exposure to toxic chemicals, especially at low-level mixtures, leads to adverse health outcomes. Instead of trying to link cause and effect, which is virtually impossible to achieve because of the lack of information and understanding, it is time to consider whether there is enough information and evidence about exposure and adverse health problems in a community to take action to protect people exposed to toxic chemicals.