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Should a potency cut-off be included in the criteria for identification of EDCs?

Certain industry sectors support a potency cut-off as a filter mechanism to be included as part of the EDC criteria so that only highly potent EDCs would be regulated. However, setting a “potency cut-off” at the identification stage would be arbitrary and have no scientific justification.

Knowledge on potency is dependent on:

a) the type of test system and observed effect;

b) the organism/species used in the test system;

c) the observed life-stage (pregnancy, late life);

d) the specific mode of action in question

Studies have shown that BPA is a very weak estrogen in some test systems, but it is reported to be equipotent with oestradiol (E2) with respect to the induction of insulin in mice [i]. If current toxicity tests examine endpoints that may be insensitive measures of hormone disruption, chemicals may be wrongly assigned as weakly potent. Therefore comparing relative potencies of chemicals can be very misleading.

A potency cut-off would also mean that weak EDCs with very high exposures could slip through the regulatory net. Even a weak EDC can interfere prenatally with hormones which are crucial for the long term development of the child [ii].

Missing weak EDCs is in particular a problem because of known combination effects which have been demonstrated in laboratory experiments. The general population is exposed to many substances from many different sources such as food, water and indoor air, which makes up a chronic cocktail of exposure.

Potency considerations do not play a role in the existing processes for identification of carcinogens and reprotoxic substances (e.g. phthalates), so they should not play a role in the identification of EDCs.

Equally, there is no potency element in the WHO/IPCS definition of EDCs. If at a later stage after identification has taken place, some priority setting is needed, differences in potency can be used as one of the elements to consider. See also CHEM Trust/HEAL briefing on EDC criteria.

This page is part of CHEM Trust’s Hormone Disrupting Chemicals FAQ – Full list of questions here.

The next question is “Are the effects of EDCs seen in the laboratory reversible?“.

 

[i]. Paloma Alonso-Magdalena, Sumiko Morimoto, Cristina Ripoll, Esther Fuentes, and Angel Nadal: The Estrogenic Effect of Bisphenol A Disrupts Pancreatic beta-Cell Function In Vivo and Induces Insulin Resistance, Environ Health Perspect 114:106–112 (2006). doi:10.1289/ehp.8451 available via http://dx.doi.org/

[ii]http://endocrinedisruption.org/prenatal-origins-of-endocrine-disruption/critical-windows-of-development/timeline-test/