recent years, although mean daily concentrations of smoke still exceed WHO guidelines.
Lead concentrations in air do not exceed WHO guidelines and have decreased since control measures prohibited leaded petrol sales in Moscow. A decrease in carbon monoxide concentrations has been observed between 1975 and 1990. However, carbon monoxide maximum concentrations frequently exceed WHO guidelines. In addition, concentrations of nitrogen oxides have increased significantly between 1986 and 1990 as a result of increased vehicle traffic and power generation.
Source: UNEP/WHO, 1992
Figure 10.4 - Annual mean concentration of smoke, CO and NO2, Moscow, 198090