The Working Group on Effects
under the UNECE Air Convention

WGE studies air pollution effects in the pan-European area and in North America based on international cooperation on research, monitoring, modelling and mapping.

Air pollution effects on nature, materials, and human health

The Working Group on Effects provides information on the degree and geographic extent of the impacts of major air pollutants, such as sulphur and nitrogen oxides, ozone, volatile organic compounds, persistent organic pollutants, heavy metals, particulate matter, including black carbon, and ammonia on human health and the environment. The Working Group on Effects provides information on policy-relevant user-friendly indicators to evaluate air pollution effects on the environment and health.

About Working Group on Effects

WGE manages six International Cooperative Programmes (ICP) and a joint Task Force on Health with the World Health Organization (WHO). For selected air pollutants they carry out:

  • Long-term monitoring of ecosystems and materials at thousands of sites
  • Intensive monitoring for research and modelling at selected sites
  • Trend exposure programme for materials and case studies at cultural heritage sites
  • Assessment of relationships between pollutant load and impacts
  • Studies on modelling and mapping of critical loads and levels for acidification, eutrophication and ground-level ozone impacts
  • Evaluation of air pollution effects on human health

Key issues/main messages

In acid-sensitive soils, lakes and streams in Europe and North America, sulphate concentrations have decreased on average 45-55% since 1988 as a result of a decrease in sulphate deposition. This has led to a widespread chemical and some, but slower, biological recovery of surface waters and soils. In 2020, critical loads were exceeded at 4% of ecosystem areas. Still, full ecosystem recovery may not occur until long after non-exceedance.

In year 2020, about 64% of the European terrestrial ecosystem area was not protected from eutrophication. Nitrogen deposition alters plant species diversity (briophytes, fungi, vascular plants), nutrient cycling, and forest growth, and interacts with climate-stressors. Although nitrogen retention in ecosystem is still high, nitrate loss to the groundwater has risen.

Human health and vegetation (including crops, trees, and semi-natural vegetation) remain currently at considerable risk of adverse impacts of ground-level ozone. Both rising background ozone concentrations from intercontinental transport and local peak episodes of ozone can cause adverse effects. Ozone impacts on vegetation are wide-ranging and include visible injury on leaves, reduced photosynthesis, reductions in crop quality and yield, impacts on whole-tree growth and productivity, and changes in community composition and reduced flower number for semi-natural vegetation.

Corrosion of all materials has decreased substantially in Europe and roughly halved compared to values measured in 1987. These reductions are a result of decreasing levels of acidifying pollutants, mainly SO2. Since the turn of the Century, however, the improvements are minor. The main challenge today is the effect of particulate matter, an important pollutant for both corrosion and soiling of materials.

Declining emissions and subsequent depositions have led to a reduction in heavy metal concentrations in mosses, with a reduction of 82% for lead (Pb), 63% for cadmium (Cd), 57% for vanadium (V) and 30% for copper (Cu) for the period 1990 – 2015. For mercury (Hg), the concentration in mosses declined by only 2% between 1995 and 2015. Mercury pollution remains a problem of global concern. The 2015 survey of heavy metals in mosses showed that the lowest concentrations of heavy metals in mosses were generally found in northern and western Europe and the highest concentrations in (south-)eastern Europe, resulting in a north-west to south-east gradient.

Reductions in total deposition of Pb, Cd and Hg between 1990 and 2012 in Europe were 78%, 53% and 23%, respectively. Cd and Pb concentrations are progressively declining in the upper layers of soils (but increasing in the lower), while Hg concentrations are increasing in some sites. Exceedance of critical loads of mercury puts ecosystems at risk. There are still sites where mercury in freshwater fish exceeds WHO and WFD environmental quality standards.

7 % of the urban population in the EU-28 was exposed to levels above the EU limit value for PM2.5, and approximately 82 % was exposed to concentrations exceeding the stricter WHO AQG value for PM2.5 in 2015.

Last updated: 2023-09-06