Dioxin: A difficult-to-define molecule entangled in hypothetical fears

I've dedicated my life to public health, working to protect the citizens of our community. As a public health official and someone who has had significant education in the sciences, I deal with as much factual information as possible and interpret data based on its own merits.

Take, for instance, the class of synthetic chemicals attacked on a regular basis for causing cancer or other maladies in humans. Synthetic chemicals are produced in a laboratory. Then there are nature's chemicals, those that occur naturally in the environment. Rarely do you read about these chemicals causing any harm to humans, even though they have the potential to do so.

Probably the easiest illustration of possible cancer-causing substances and risk is to look at how research defines it. The EPA elects to base its estimates of toxicity risks on high-dose animal experiments, usually in rats. Rats are subjected to very high exposure levels of a chemical daily over the course of their lives and the data are then used to assess what can possibly happen to humans at typical environmental exposure, which are often thousands to millions of times less.

This is one reason why we have an absence of human evidence for harmful effects. Other reasons include the possibility that animals don't predict human response, the high doses used to overwhelm normal defense mechanisms that protect the animal or that a threshold for adverse effects might actually exist. It's not for the lack of trying to find evidence of adverse effects. In addition to animal studies, the federal government as well as private groups have studied a large number of populations of people who have been or might have been exposed to dioxin and other chemicals in the workplace or environment without identifying significant medical findings. Chloracne, which is a skin rash, was found at comparatively high exposures after occupational exposure to dioxin.

Consider nature's chemical factory. The cup or two of coffee you may have had for the past many years for instance? Consider that coffee, among other natural compounds, contains benzo pyrene (considered by EPA to be a mutagen and rodent and human carcinogen), benzaldehyde (EPA rodent carcinogen), benzene (rodent and human carcinogen), caffeic acid (EPA rodent carcinogen), hydrogen peroxide (EPA mutagen and rodent carcinogen).

This is just a small sample of the types of natural chemicals found in food and beverages, but of the hundreds or thousands of compounds labeled carcinogens by regulatory agencies, only about 25-30 are recognized as causing cancer in humans.

Contrary to common perception, 99.99 percent of the chemicals humans ingest are natural. The amounts of synthetic pesticide residues in plant foods, for example, are extremely low compared to the amounts of natural pesticides produced by plants themselves (i.e., isothiocyanates in celery or cardiac glycosides in potatoes).

But don't become paranoid about these chemicals, for you would have to consume more than most elephants would consume over a period of years to have any chance of negative effects. And if you look at America's longevity, it continues to rise as each decade passes. We must be doing something right.

Then there is dioxin. A complex, difficult-to-define molecule that resulted in a billion-dollar industry measuring its toxicity, assessing its risk and cleaning it up.

A tremendous amount of money has been spent for research, meetings, lawsuits and environmental cleanup of this chemical by the government, both federal and local, and many scientists and lawyers have made a lifelong commitment to chasing dioxin. However, we should ask ourselves: What are we gaining from all this activity, aside from people making a lot of money?

If the public is proven to be at risk and is particularly vulnerable to trace levels of dioxin or any environmental chemical for that matter, then we need to promote the appropriate restrictive regulatory policies regardless of cost.

If, however, the science leads us to the conclusion that our public is not more vulnerable to this or any of these synthetic chemicals, then the justification for such expenditures evaporates, and expending our limited resources on purely hypothetical, unscientific forms of protecting the public would only distract us from policies that focus on real health threats to our community. And we have plenty on which to focus.

Risk is the key term here. Risk involves exposure and a dose that is capable of causing harm. There is a level of exposure and given dose of a substance whereby there is no adverse health effect on humans. And then there is a level above which an effect may become apparent. Without either exposure or toxicity, or if one or the other or both are very small, risk is low or nonexistent.

Almost everything we do involves some sort of risk; some are quite small, such as being hit by lightning (two per 100,000 people per year), or the unlikely risk of dying as a result of a commercial plane crash (six per 100,000 people per trip), or even dying from a simple vaccination (three per 100,000 people per year).

The main emphasis here is to ask the question: What is an acceptable or reasonable level of risk, because risk in our lives is a daily event. Do you feel safe flying in a commercial airline, given the above level of risk?

Nobody is arguing that TCDD (dioxin) is not toxic (all chemicals are toxic, even water, depending on dose as mentioned previous) and can cause certain problems in animals at high levels.

There is much that can be said about the recent and significant University of Michigan study (umdioxin.org) by Dr. David Garabrant and his group. One noteworthy factor is that the people who live in the Tittabawassee River floodplain have only 7 parts per trillion (ppt) higher median TEQ levels in their blood than those living in Jackson/Calhoun counties, as well as the entire nation. The difference of 7 ppt is so small that it is negligible.

Does this 7 ppt difference just happen to exceed the health threshold between a diagnosed and confirmed related ailment or not? Are these people in all reality at more risk than people in the control counties or the nation? Of course they are not.

This very small difference is due to the age and body mass of the population (dioxin and related compounds increase as we age), the long half life of these compounds in the body, past exposures to high levels in the workplace or local environment, and the large number of people studied that enables us to detect this difference.

The University of Michigan Dioxin Exposure Study found little or no evidence of any impact of the specific dioxins and furans in area soils and local game and fish on blood levels of these specific compounds in local residents. These findings do not support the common regulatory human health risk assessment assumption that soil (or house dust) are significant sources of exposure to these environmental residues, nor do they support the conclusion that consumption of local game, deer, and fish have resulted in increases in the blood levels of dioxins and furans beyond those associated with consumption of these foods from any other source.

A part per trillion (ppt) is approximately equivalent to one second in 317 centuries of time, or 1 inch in over 657 trips around the Earth's equator.

Science and our understanding of it change as we complete new studies and develop new technology, and our government agencies must also change as new information becomes available. What was acceptable as precaution in the absence of knowledge 30 years ago no longer has the same relevance.

Not accepting sound science and change is a disservice to not only our valuable industrial base in this state, but to all the community as well. If these same agencies do not change their methods based on sound scientific studies, then our elected officials must intervene.

Environmental cleanup levels set in the past were not based on any or all of the data available for dioxin, for instance, and should be changed.

This is critical so as to not expend unnecessary resources financial or otherwise on processes that are based on little or no scientific data and provide no additional safety for the public.

- Chuck Lichon is Midland County Environmental Health Services director. He has a bachelor's degree in Environmental Health from Ferris State University and a master's in Public Health from the University of Michigan, as well as being registered with the State of Michigan as an environmental health specialist. He is a lifelong Tri-Cities resident, a hunter, fisherman and has been instrumental in raising a quarter-million dollars for waterfowl and wetlands restoration in the Saginaw River Watershed.