The significance of the WHO air quality guideline values 2021 for the Swiss Ordinance on Air Pollution Control
To protect the population and the environment from excessive air pollution, the Ordinance on Air Pollution Control (OAPC) of 1985 set ambient air quality guidelines (AQG) for a number of pollutants and complemented them in 1998 and 2018. National and international research over the last 20 years has now shown that adverse health effects can also occur at significantly lower concentrations of air pollutants. Therefore, after a comprehensive review of the current state of knowledge, the WHO lowered the guideline values in 2021 in the new Global Air Quality Guidelines.
Based on the current state of knowledge and taking into account the new WHO guideline values the FCAH recommends adapting the OAPC and thus lowering or supplementing the AQG for the six pollutants sulphur dioxide SO2, nitrogen dioxide NO2, carbon monoxide CO, ozone O3, particulate matter PM10 and PM2.5. The other AGQ are to remain unchanged. The FCAH is not currently recommending AQG for air pollutants that have not yet been regulated. However, it supports the good practice statements about soot and ultrafine particles UFP formulated in the WHO's 2021 air quality guidelines. These emissions must be avoided as far as possible.
Measurement and health risks of suspended particulates and fine particulate matter
To protect the public against excessive exposure to particulates in ambient air, air quality standards for "total suspended particulate matter" were specified in the Ordinance on Air Pollution Control (OAPC) of 1985.
In the following years studies showed that health effects occur even when these limits are complied with, and that respirable particles with a diameter of less than 10 microns (PM10) are key indicators for assessing the impact of air pollution on human health.
The FCAH therefore recommended that the Federal Council should revoke the standards specified in the OAPC for "total suspended particulate matter" and replace them with standards for PM10. The proposed values were adopted when the OAPC was amended in 1998.
In 2013 the Swiss Federal Commission for Air Hygiene has summarized and evaluated the latest research findings on adverse effects of ambient particulate matter on human health. In its report it recommends incorporating an additional ambient air quality standard for smaller particulate matter (PM2.5) into the Ordinance on Air Pollution Control (OAPC).
Despite considerable reductions in emissions of ozone precursors - nitrogen oxides and volatile organic compounds (VOCs) - exposure to photochemical smog in Switzerland during the summer months often, and for lengthy periods, exceeds the ambient air quality standards specified in the OAPC. This may adversely affect the health of sensitive individuals and also damage vegetation.
To ensure effective protection, further measures are required to reduce exposure levels, with the emphasis being clearly placed on measures with lasting effects. The approach defined in the Federal Council’s report on federal and cantonal air pollution control measures should be adopted as rapidly as possible. While emergency measures can help to alleviate overall exposure, they are no substitute for measures of lasting efficacy.
At the beginning of the ozone season and whenever limits are exceeded, the public should be appropriately informed about the ozone issue, possible effects and measures to prevent excessive exposure.
Air pollutants containing nitrogen
In Switzerland, levels of air pollution with nitrogen oxides and ammonia are clearly too high. In its status report, the FCAH calls for a 50% reduction in emissions of nitrogen oxides and ammonia. It recommends that the best available technology for reducing emissions should be consistently applied nationwide.
There is a particular need for remedial action in the agricultural sector, since insufficient use is made of low-emission techniques in the management of manure from livestock farming. Nitrogen oxides and ammonia are harmful to near-natural ecosystems and human health. The application of known measures could help to achieve the goal of reducing emissions to a level that is acceptable from a health and environmental viewpoint.
The FCAH examined options enhancing the implementation of emission reductions in agriculture. The possibility to use critical loads for nitrogen – in special cases critical levels for ammonia as well - as assessment criteria should be mentioned explicitly in the OAPC. These internationally approved values are based on criteria equivalent to those of the Swiss Environmental Protection Act, having therefore the same significance as air quality standards.
Risk of cancer from diesel and petrol engine exhaust emissions
Diesel engines not fitted with efficient filters emit 100 to 1000 times more fine soot particles than petrol engines. Of particular concern from a health perspective are the respirable solid particles contained in the emissions. In cities and built-up areas, diesel soot particles account for up to 70% of the cancer risk attributable to air pollution.
According to the Environmental Protection Act and the Air Pollution Control Ordinance (OAPC), emissions of carcinogenic air pollutants are to be minimized in order to protect public health.
Benzene, a carcinogenic air pollutant
Benzene is released in emissions from cars with petrol engines, from two-stroke engines and petrol pumps with defective vapour recovery. At the end of 2000, the EU specified a limit value for benzene concentrations in ambient air.
In the light of the EU proposal, the FCAH position paper reviews air pollution control regulations for benzene in Switzerland and proposes further action. According to the analysis by the FCAH, the EU limit value for benzene does not fulfil the requirements of the Swiss Environmental Protection Act; a more ambitious emission target should stimulate additional measures to reduce exposure to benzene and ensure long-term protection of the public.