I highly recommend reading this article from last week’s Scientific American.

It’s an interview with Linda Birnbaum, the toxicologist who leads the National Institute of Environmental Health Services (NIEHS) and the National Toxicology Program (NTP).

She makes some interesting statements.

How much of human disease is due to environmental exposures?
The estimates vary, and it depends on how you define environment. People often say it’s about 30 percent. I think that’s defining environment fairly narrowly, considering only environmental chemical exposures, but your environment includes the food you eat, the drugs you take, the psychosocial stress you’re exposed to and so forth. After all, what’s the difference between a drug and an environmental chemical? One you intentionally take and the other one you don’t. Considering all that, I would say then the environment is much more than 30 percent.

Why has it been so difficult to link environmental exposures to specific health consequences?
Nobody is exposed to one chemical at a time, right? I mean we live in a soup of chemicals and we live in a soup of exposures. Here, I’m having a lemonade. Well, it’s not only lemon in here. I’m sure there’s some sugar. There might be a preservative or something. I don’t know what’s in this. So think of all those things interacting, but when we test chemicals in the lab we tend to test them one at a time.

I guess we don’t consider these other types of exposures.
Right. A high-fat diet, for example, can completely change the way your body handles chemicals. Exposure to a certain chemical may lower your ability to respond to an infection. At EPA we did a lot of studies exposing rats and mice to air pollutants and then to bacterial infections or influenza infections. Those who were exposed to pollution were more likely to die, whereas those in clean air recovered.

PCBs are considered likely carcinogens, but they are also endocrine disruptors, like bisphenol A or dioxin, which is something we’ve heard a lot about in the media lately. What is your definition of an endocrine disruptor?
An endocrine disruptor is anything that affects the synthesis of a hormone, the breakdown of a hormone or how the hormone functions. We used to think it had to bind with a hormone receptor but endocrine disruptors can perturb hormone action at other stages in the process.

Why are they such a big deal?
They’re all around us, and I think they can affect us at very low levels. Our hormones control our basic homeostasis, our basic physiology. If you alter your hormone levels, you’re not going to behave the same way physiologically, and that includes mentally and everything else. I think that there’s growing evidence that some of the chemicals to which we are exposed are doing that to the population right now.

How has spending 33 years studying toxic chemicals affected your outlook on the environment?
We do know that there are many chronic health conditions, non-communicable health conditions, which have increased too rapidly in the last 20 to 40 years. These are things like autism, ADHD and, of course, obesity and diabetes. We have identified chemicals clearly at play in the obesity epidemic. I am not in any way saying to people you can stop exercising and you don’t have to watch what you eat, but the question I have is: Are we setting people up to fail because they’re exposed to something that alters their ability to metabolize fats or sugars?

Source: Scientific American: Chemical “soup” Clouds Connection ebtween Toxins and Poor Health

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