Estimation of the health impact of environmental pollution and quantitative health risk assessment.
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The quantitative health risk assessment (QHRA) was developed in the early 1980s by the Academy of Sciences in the USA. This is a method put forward to shed light on risk management, aiming to provide an estimation of the human health risk in a context of scientific uncertainty, particularly as regards chronic exposure of low intensity to hazardous agents in the environment. In France and abroad, its scope is extending. |
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The two immediate results of a QHRA are the excess of individual risk (EIR) and the hazard quotient (HQ). Using what is known about the numbers of people exposed, a number of expected cases of disease and/or percentage of the population likely to fall ill can be calculated; they represent a population expression of the health consequences of the exposure considered, still known as health impact. This expression is increasingly used for communication and backing up decisions, whether this involve for example appreciating the extent of the public health problem, adjusting a polluting emission authorisation or analysing the relevance of setting up an epidemiological study. The challenge is therefore to effectively identify and determine the purpose of the QHRA conducted.
This methodological approach was implemented in 2002 to study the health impact of the household waste incineration plant in Angers. Controversy broke out after the announcement of 18 predicted cases of cancer over the next 70 years in the population exposed for 25 years to the atmospheric emissions of this plant. Accordingly, in 2002, the Director General for Health (DGS) asked the French Institute for Public Health Surveillance (InVS) and the French Agency for Environmental Health (Afsse) to draft “a report on the use of the risk assessment method so that professionals and parties concerned can identify the objectives and approach and understand and use its results more effectively.” The main French public agencies and institutes specialising in the expert assessment and watch of environmental health and safety and implementing or teaching quantitative health risk assessment were invited to contribute.
In 2002, the DGS asked the InVS and Afsse to work together on the drafting of “a report on the use of the risk assessment method so that professionals and parties concerned can identify the objectives and approach and understand and use its results more effectively.” The main French public agencies and institutes specialising in the expert assessment and watch of environmental health and safety and implementing or teaching quantitative health risk assessment were invited to contribute.
Working method (procedure):
During this project, the members of the working group (WG) created sought to lay the conceptual and methodological foundations to give a unified insight into the QHRA exercise, beyond the circumstances in which it is applied. The WG mainly endeavoured to reveal the validity and appropriateness of calculating the health impact when the hazard concerns carcinogenic potential. However, it did not want to go into aspects concerning the perception and communication of QHRA results, for which the group would have required other skills, particularly in human and social sciences. Lastly, all of the WG members agreed that it was not about producing a practical guide for applying the QHRA approach.
As requested by the DGS, this report was drawn up to address all sorts of people: health risk assessors, risk management professionals such as civil servants and study commissioners (manufacturers, local authorities, etc.). It was organised in such a way that each person could find the ideas necessary for taking action.
This document is a provisional version available for public comment from all readers.
Comments can be sent to the following email addresses: impact-sanitaire@afsset.fr or impact-sanitaire@invs.sante.fr
Following this public revision, the working group that drafted this document will study all of the comments made with a view to drawing up the definitive version of the document.
During this project, the members of the working group (WG) created sought to lay the conceptual and methodological foundations to give a unified insight into the QHRA exercise, beyond the circumstances in which it is applied. The working group was formed on this basis. From the occupational context to non-occupational environments (“natural environments shaped by man” or the field of consumer products), from the field of ionising radiation to the vast register of toxic risks and to that of infection risks, QHRA practices have been developed over time, often simultaneously, due to the low interpenetration of the scientific and professional communities concerned. The analysis conducted revealed that there are real similarities today, despite continuing heterogeneous terms. The radiological risk field was the forerunner, initiating the approach. It is distinctive because its data are often obtained from human epidemiological observations (in the context of war, industrial accidents, occupational epidemiology in the mining environment, radon and in the home). Quantitative hazard estimators for chemical risks come mainly from animal testing today, much less from epidemiology even if this source of knowledge is gradually increasing.
The QHRA approach comprises four stages: (i) hazard identification, (ii) estimation of the dose-response relationship, (iii) estimation of exposure and (iv) risk characterisation. Each stage requires a scientific assessment which aims to summarise the available knowledge, producing a review of what we know, what we don’t know and what remains questionable. The two indicators calculated at the end of this approach are a hazard quotient (HQ) and an excess of individual risk (EIR). These two indicators are used to calculated an actual health impact (HI), with account taken of the population in question.
The critical points, hypotheses and uncertainty of each QHRA stage have been analysed in a report which, in line with the DGS’s request, had to address all sorts of people: health risk assessors, risk management professionals such as civil servants and study commissioners (manufacturers, local authorities, etc.). It was organised in such a way that each person could find the ideas necessary for taking action.
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