While the toxic effects of certain substances have been clearly established at high doses, the question of identifying harmful effects linked to long-term hormonal disturbance, or even across several generations, and potentially at low doses remains currently posed.
The low exposure dose
Usually, below a certain level of exposure, the body’s defense mechanisms prevent the onset of health effects. This is called a threshold effect. For certain dangerous substances such as carcinogenic molecules, we observe that there is sometimes no threshold effect, at least on the scale of a population therefore, of possible effects even at low doses. Endocrine disruptors are suspected of acting in the same way.
Non-monotonic dose-response relationships
Traditionally, the harmful effects of chemicals are described in toxicology studies as proportional to the dose tested. Typically, a low dose produces no effect, the middle dose produces weak toxic effects while the high dose tested induces more pronounced or more deleterious effects. But, toxicologists have noticed that certain chemical substances can follow inverted curves, that is to say have greater effects at low doses (even opposite) to those observed at high doses, we then speak of non-response dose. -monotone.
“Exhibition Windows”
Sensitivity to endocrine disruptors can vary according to the periods of life. This is particularly the case of the period of fetal-embryonic development, early childhood, which present an increased sensitivity to some of these substances. The onset of puberty is also a sensitive period during which a hormonal imbalance can irreversibly alter certain functions of the body.
« Effets cocktails »
Understanding the effects of endocrine disruptors also requires taking into account the exposure of the individual to a mixture of chemical substances and understanding their interactions within the human body over the long term, from the period of fetal-development. embryonic.
Faced with this complexity, knowledge of the effects of endocrine disruptors at the concentration levels observed in the environment comes up against the limits of conventional toxicology and the usual methods of risk assessment. The question is therefore to develop new ones, adapted to the specificities of these compounds. Understanding the potential effects of the environment on the health of populations requires that research projects consider the potential synergistic effects of mixtures of environmental contaminants.