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Outdoor workers and regulating air quality

Though outdoor workers face a range of risk-factors to their health, safety and wellbeing, any relative risk associated with ambient air pollution has tended to fall between those responsible for regulating occupational and public health risks.

A Minister for DWP that sponsors the Health and Safety Executive says that it does not regulate environmental exposures and (as of February 2019) is not currently undertaking any research to better understand the effect of polluted ambient air on the health of outdoor workers.

In the workplace, the Control of Substances Hazardous to Health (COSHH) regulations contain much of the legislation used to control harmful inhaled exposures at work. A key tool for managing such risks is the Workplace Exposure Limit (WEL) but given where outdoor workers work, a WEL cannot effectively operate in the ambient environment.

Environmental laws also seek to limit people’s exposure to air pollution. The 2008 ambient air quality directive (2008/50/EC) sets legally binding limits for concentrations in outdoor air of major air pollutants that impact public health such as particulate matter (PM10 and PM2.5) and nitrogen dioxide (NO2).

This Directive was made law in England through the Air Quality Standards Regulations 2010

If we look at the relevant UK Air Quality limit values and compare them (though this is indicative as the reference period varies for these exposures) with Workplace Exposure Limits then we can see how the regulations are potentially failing to address the risk of long-term exposure to ambient air pollution.

Comparing WELs with Air Quality Standards Regulation 2010


UK WELs Limit Value

milligrams per cubic meter (mg/m3)

UK AQS Limit Value

milligrams per cubic meter (mg/m3)

WHO limits

Nitrogen dioxide (NO2)

0.96 mg/m3 for an 8 hour TWA reference period


1.91 mg/m3 for a 15-minute reference period

0.2 mg/m3 for 1- hour mean


0.04 mg/m3 for annual mean

0.2 mg/m3 for 1-hour mean



0.04 mg/m3 for annual mean

Ozone (O3)

0.4 mg/m3 for a 15-minute reference period

0.1 mg/m3 for 8- hour mean

0.1 mg/m3 for 8-hour mean

Particulates PM10


0.05 mg/m3 for a 24-hour mean


0.04 mg/m3 for an annual mean

0.05 mg/m3 for a 24-hour mean


0.02 mg/m3 for an annual mean

Particulates PM2.5

Carbon Black[1]  has a WEL of 7 mg/m3 for a 15-minute reference period

0.025 mg/m3 for an annual mean

0.01 mg/m3 for an annual mean


0.025 mg/m3 for a 24-hour mean

We can see in the table above, for example, how the limit value for nitrogen dioxide under workplace regulations is nearly 5 times higher than the environmental limit.

For those whose place of work is the ambient environment, they will never, in all likelihood, face exposures that exceed limits set by COSHH. Yet with all the evidence on the health impacts of air pollution, are we really saying that the ambient environment presents little or no risk and that exposure to ambient air pollution doesn’t need to be monitored or controlled?

[1] Carbon Black is a major component of PM2.5 and is associated with road traffic emissions, see Defra Air Quality Expert Report, 2012