Published: 10-06-2013 00:00 | Updated: 23-02-2014 14:33

Safer risk assessment of endocrine disruptors

A new doctoral thesis from Karolinska Institutet shows that it is important to enhance the usefulness of academic research (non-standardised research studies) for risk assessment of endocrine disruptors. Traditionally, less importance is often attached to research studies than to standardised tests in risk assessment. However, according to the current thesis, academic studies may be better designed to investigate sensitive effects of these substances.

Health risk assessment aims to identify the negative effects that can be caused by a substance and the levels at which harmful effects may occur. Essentially, the endocrine system regulates all the organs, tissues and cells in the body and controls vital functions such as reproduction, growth and development. The foetal period, when various organs and tissues develop, is particularly critical.

There is much uncertainty with respect to risk assessment of endocrine disruptors. It is known that these substances affect the functions of the endocrine system and can cause effects at very low doses. However, they can also cause different - and even opposing - effects at high and low doses in animal studies. The effects are often very subtle and sometimes do not appear until long after exposure to the substance has ceased. These properties contradict a number of the toxicological assumptions and principles on which risk assessment is traditionally based.

In the risk assessment process, e.g. in accordance with the EU's chemical regulation REACH, the authorities often attach the greatest importance to toxicity studies carried out in accordance with internationally agreed and standardised tests, which are considered to be very reliable. However, these tests can miss the effects specific to endocrine disruptors, such as delayed effects and effects at very low doses.

"We humans are exposed to a large number of chemicals every day. Many of these have proven to be capable of disrupting the regular function of the endocrine system in experiments," says Anna Beronius, doctoral student at the Institute of Environmental Medicine at Karolinska Institutet. "A number of links have been reported between endocrine disruptors and hormone-related diseases in humans over the past few decades, which may indicate that our methods for risk assessment and regulation of chemicals to date have been insufficient to protect human health."

The purpose of the thesis work was to examine how the scientific uncertainty concerning the toxicity of endocrine disruptors can be reduced or handled in order to make health risk assessment more reliable. The thesis work has examined the risk assessment process for endocrine disruptors within the EU, along with the toxicity data available to risk assessors and how the use of all available toxicity data can be improved. The much debated substance bisphenol A (BPA) has been used as a case study for much of this work.

The results show that non-standardised research  that is to say, studies generated within academic research not conducted according to standardised test guidelines  contributes information which could result in safer risk assessment for endocrine disruptors. The thesis work has also developed methods for enhancing the usefulness of academic research studies in the health risk assessment of chemicals.

This research has been financed by the Formas research council and the CASCADE Network of Excellence research network within the EU's sixth framework programme. Professor Annika Hanberg has supervised the work. Defence of the thesis will take place on 31 May 2013.

Doctoral thesis

Risk Assessment of Endocrine Disrupting Compounds
Anna Beronius
Institute of Environmental Medicin, May 2013, ISBN 978-91-7549-144-8