Understanding Toxicity

Toxicologist Gary Perdew explains why it’s difficult to measure the impact of toxic exposure on human health.

illustration of skull and crossbones with rulers as crossbones on red background by Richard Mia


“Most of us don’t live in hermetically sealed, controlled environments. Consequently, we’re continually and increasingly exposed to a multitude of chemicals. I study the long-term health effects of dioxin, a synthetic chemical and a carcinogen. In the rodent models we use, continual exposure seems to participate in the development of cancer. We’re trying to understand biologically how that happens and what doses of exposure are significant.

“Clearly, it’s important to limit one’s exposure to carcinogens and other toxic chemicals. People who live close to industrial situations, like the residents of East Palestine, Ohio, where a train derailed in February, don’t have a choice, of course. The decision to burn vinyl chloride in the aftermath of that derailment was, in my opinion, a good decision. Vinyl chloride is a carcinogen, so not only would high-dose exposure have immediate adverse effects on the population in the vicinity, there could also be long-term effects, including increased risk of cancer. The chemicals present after burning have their own toxicity, but that will disappear. Vinyl chloride is much more persistent.

“Still, doing a robust epidemiological study is hard. Epidemiological studies work best on homogenous populations, but heterogenous populations are the reality, so it becomes a trade-off, as homogenous study groups may give accurate cause-and-effect data at the expense of real-world situations. Properly studying the long-term health impact of toxic exposure to synthetic chemicals also means understanding the meaning of the word ‘toxic.’ Saying something’s toxic doesn’t have much meaning until you talk about amounts. The dose you’re exposed to makes the difference.”