QMark: Population and health in EIA

Tara Barrett explains how taking a quantitative approach to health impacts can add value to an EIA

Nearly three years on from the 2017 update to the EIA Regulations, ‘population and health’ remains a poorly understood topic in EIA.

Assessing health in an environmental context is a niche area of expertise, but it is necessary. The lack of clarity around how to assess population and health effects can leave practitioners unsure. This could see the population and health topic fail to effectively mitigate adverse effects on local community health, and consequently be targeted as a weak link in the EIA process.

While population and health explicitly became part of the regulations in 2017, many inter-related technical disciplines, such as air quality and noise, already include protection of human health in their assessments to some extent. After all, the protection of the environment is inherently conducive to protecting human health. 

However, we can go further – and this is where the specific inclusion of population and health in the updated regulations adds value. While potential population and health effects are influenced by a range of environmental, social and economic health determinants, which are scoped on a project-by-project basis, this article will us air quality and noise health determinants to demonstrate how an assessment of population and health adds value, including discussion of how and why quantification of health effects is beneficial. 

Air quality 

Air quality assessment levels (AQALs) form an important part of air quality assessments. Effects on human health receptors are judged based on whether AQALs are predicted to be exceeded, how close air quality concentrations are to the AQAL, and the change in concentration as a percentage of the AQAL. While AQALs are set to protect the environment and health, health effects may be experienced at concentrations below these limits; based on available evidence, there may not be a concentration threshold below which no adverse health effects occur. 

The relationship between exposure to air pollution and specific health outcomes is well understood and the evidence base is robust. As such, the application of quantitative assessment methods in these circumstances is beneficial in further communicating the significance of effects on human health. 

Our approach to assessing health effects associated with changes to air quality provides further context and added value to air quality assessment outputs. This is done by drawing from and building upon the absolute change in air quality concentrations to calculate predicted changes in specific health outcomes (such as emergency hospital admissions) for the local population. Specifically, we apply concentration response functions detailed in various consensus assessments, such as the World Health Organization Health Risks of Air Pollution in Europe exercise, UK advisory group the Committee on the Medical Effects of Air Pollutants, and/or Kings College London’s Environmental Research Group.

With the weight of globally recognised concentration response functions and assessment methods, a quantitative population and health assessment can refine the health assessment, better inform the application, and more effectively respond to and address community concerns and risk perceptions. 


The noise health evidence base is more complex than for air quality, as there are both toxicological and subjective parameters that can influence population and health outcomes. Unlike the air quality evidence base, there is an absence of consensus assessments on the effects of noise exposure on health outcomes. This makes it far more complex and diverse to source information to apply in quantitative assessments. Furthermore, it may be beneficial not to use the WebTAG noise appraisal method of quantifying the health impacts of noise exposure, which assigns a monetary value to each disability-adjusted life year lost or gained, because in many cases it is not necessary to monetise health outcomes – which should have substantial weight on their own.  

While factors such as absolute change in noise exposure and number of people affected may be taken into consideration somewhat by the noise assessment, thresholds for the lowest observed adverse effect level (LOAEL) and significant observed adverse effect level (SOAEL) generally form the basis of the noise assessment. 

Where considered proportionate, RPS’s Health Impact team will apply quantitative assessment methods in assessing health effects associated with changes in noise exposure (generally for aviation projects). A quantitative approach provides further context and added value to noise assessment outputs by using the absolute change noise exposure, above a defined LOAEL, to calculate predicted changes in specific health outcomes (such as stroke incidence and mortality) for the local population.

As changes in noise exposure are complex and their impact on health can be influenced by a range of factors (not just being above or below the LOAEL), the application of quantitative assessment methods to assess population and health effects from changes in noise exposure is particularly beneficial to further communicate the significance of effect on human health.


While there is a lack of clarity on how to assess population and health effects, the demonstrable success of the RPS Health Impact team in delivering population and health assessments since the update to the regulations, using the quantitative methods outlined above, is proof that the topic does not have to be the weak link in an EIA. Overall, the assessment of population and health can provide added value to inter-related topics and help strengthen conclusions using quantitative exposure response calculations to better address community concerns and risk perceptions. 

Tara Barratt is senior health impact assessment consultant at RPS Group

Image credit | iStock
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