Diane Benford

Implementing systematic review techniques in chemical risk assessment: Challenges, opportunities and recommendations

Systematic review (SR) is a rigorous, protocol-driven approach designed to minimise error and bias when summarising the body of research evidence relevant to a specific scientific question. Taking as a comparator the use of SR in synthesising research in healthcare, we argue that SR methods could also pave the way for a step change in the transparency, objectivity and communication of chemical risk assessments (CRA) in Europe and elsewhere. We suggest that current controversies around the safety of certain chemicals are partly due to limitations in current CRA procedures which have contributed to ambiguity about the health risks posed by these substances. We present an overview of how SR methods can be applied to the assessment of risks from chemicals, and indicate how challenges in adapting SR methods from healthcare research to the CRA context might be overcome. Regarding the latter, we report the outcomes from a workshop exploring how to increase uptake of SR methods, attended by experts representing a wide range of fields related to chemical toxicology, risk analysis and SR. Priorities which were identified include: the conduct of CRA-focused prototype SRs; the development of a recognised standard of reporting and conduct for SRs in toxicology and CRA; and establishing a network to facilitate research, communication and training in SR methods. We see this paper as a milestone in the creation of a research climate that fosters communication between experts in CRA and SR and facilitates wider uptake of SR methods into CRA.

Risk--what is it?

Risk has been defined by the World Health Organization International Program on Chemical Safety as the probability of an adverse effect in an organism, system or (sub) population caused under specified circumstances by exposure to an agent. This article addresses some of the key components of this definition. Determining risk is dependent on expert judgement of the overall body of evidence relating to adverse effects or hazards. Such evidence can come from a range of experimental and observational studies and reports. Ideally determining risk to humans would be based upon evidence from humans rather than from experimental animals but this is generally not feasible. Even when epidemiological studies are available there can be difficulties in ascribing a disease to a causal chemical agent, and there are inevitable limitations in assessing exposure. Whilst probability refers to a mathematical or statistical quantification of the proportion of a population at risk of adverse effects, it is more common to compare point estimates of exposure with health-based guidance values.