But even at these low levels, scientists are seeing evidence of serious health effects. Humans don't respond to dioxin at the same level as all test animals, but these results certainly urge caution when it comes to this chemical. Especially when you consider that some people have much higher dioxin levels than the average for the general population. People who are subsistence fishers, or who fish regularly from a water source with elevated dioxin levels can have very high levels. And people who work in dioxin-generating industries may have higher exposure as well.
Fish are also very sensitive to dioxin.
The species found to be most sensitive are lake trout native to the Great Lakes. Their eggs begin to show significant mortality at dioxin doses as little as 40 parts per trillion. And all of their eggs die by 100 parts per trillion. It attaches to cell receptors that are designed for regulatory hormones and enzymes. It entered our environment in significant amounts with industrial expansion and the post-World War II explosion of the chlorine and petrochemical industries.