ABSTRACT
Measuring air quality is a precise science that must, by its nature, be carried out under imprecise and unpredictable conditions. Standardized international measurements are only available for a scattering of cities, and drawing comparisons from city data is difficult because of wide variations in place, time and the frequency of air monitoring samples. Sometimes, indeed, monitoring is only carried out at sites where there is a
This map depicts urban levels of three major air pollutants-sulphur dioxides, nitrogen oxides, and particulates (‘dust and dirt’). Ninety percent of anthropogenic sulphur dioxide emissions are from the burning of certain fossil fuels; nitrogen oxides come primarily from car and truck emissions; and particulates from both cars and fossil fuel combustion. All three contribute to a range of respiratory illnesses, including bronchitis, pneumonia, asthma and lung cancer, although the health effects vary with the intensity and duration of exposures. Both sulphur dioxide and nitrogen oxides are major components of acid rain and nitrogen oxides are also a minor greenhouse gas.
