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It is one of the most debated questions in chemical risk assessment: can exposure to chemicals such as pesticides cause ill health in humans?

Scientists currently rely on experimental toxicology evidence, such as animal or cell studies, to assess their safety. A new approach proposed by EFSA will help further our understanding by making better use of epidemiological studies on human health.

Human epidemiological studies have suggested an association between exposure to certain chemicals and human diseases. However, as an association does not necessarily prove a cause-and-effect link, firm conclusions cannot easily be drawn from epidemiological studies. This means that such studies are in many cases of limited use in determining whether a chemical can ultimately represent a risk factor for a disease.

In 2013 EFSA published the results of a literature review on epidemiological studies linking exposure to pesticides and health effects. Since then the Authority’s pesticide experts have been exploring how results from epidemiological studies can be integrated into pesticide risk assessments. Although this work is relevant for all chemicals, it is particularly important for EFSA’s assessments of applications for approval of pesticides, as EFSA is obliged by EU regulations to evaluate epidemiological findings.

As part of this effort, EFSA’s Panel on Plant Protection Products and their Residues has tested a method that could enable risk assessors to establish a biological cause-and-effect link between exposure to chemicals such as pesticides and ill health. Dr. Susanne Hougaard Bennekou, chair of the working group that developed the method, and Dr. Andrea Terron, an EFSA staff scientist specialising in pesticides, explain the significance of the work.

What was the aim of the project?

Pesticide risk assessors want to make better use of the information contained in epidemiological studies. To do this, we need to find a way of confirming – or not confirming – the associations suggested by the studies. This task is particularly difficult when the data relate to complex human diseases. Sometimes there are so many factors involved that it is just not possible to confirm the chemical-disease associations suggested in epidemiological studies.

In our Scientific Opinion we have applied a framework that could establish whether there is a plausible link between the cause – a chemical coming into contact with and affecting an organism at cellular level – and a subsequent chain of events leading to the effect i.e. disease. In other words, to establish whether a specific sequence, or pathway, of events represents a human health hazard – and consequently identify chemicals that need to be considered as potential risk factors for the disease.

This conceptual framework is known as the adverse outcome pathway (AOP). It was developed by the scientific community and implemented through the OECD to improve understanding of how chemicals induce adverse effects, but this is the first time that it has been adapted specifically for improving the use of epidemiological data in risk assessment.

Source: European Food Safety Authority

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