Therefore a short period of exposures exceeding the accepted limit values ten or even hundred times, would not remarkably change our body burden accumulated during the previous decades. Presently the effects have been proven only in the case of chloracne. The effect that has caused the greatest public concern is cancer, and IARC recently classified TCDD as a human carcinogen. Another concern in the society is the possible developmental effects. There is some data that dioxin exposure from breast milk is associated with abnormal development and mineralization of teeth.
Risk assessment is tricky.
A problem in dioxin risk assessment is to evaluate the actual effect of the very low concentrations in the environment of these very toxic compounds. There is wealth of information on environmental concentrations, levels in humans, epidemiological studies with indirect exposure information, effects after different exposures in animals, and on certain aspects of biochemical pathways. However, there are very few studies that are fully relevant for human risk assessment. Therefore the scientific community remains divided in the issue of the true risk of the present environmental concentrations of dioxins, and recommendations for tolerable daily intake values have varied even thousandfold between countries. There is, however, a fair agreement that the risk of cancer, while probably true at very high industrial or accidental exposures, is not very high.