Atmospheric pollution

Traditional problems related to atmospheric pollution concerned the immediate impact of industrial/domestic processes on the local environment. Very often this meant the impact of smoke resulting from the burning of coal or in earlier times wood. This aspect of atmospheric pollution is important: the average adult male has a daily consumption of:

* 1.2 kg food;

* 2 kg water;

* 13.5 kg air.

Problems are not only the preserve of the modern era. In the early 14th century, Edward I (‘Hammer of the Scots’) forbade coal burning in London while parliament, allegedly on pain of death, although it may have been a severe fine. Eye irritation was first complained of in LA in 1868. Major problems from smog (smoke+fog) were evident in London from the 19th century. This problem arose form the smoke created in the burning of bituminous coal (rich in tarry hydrocarbons; burns readily with a smoky yellow flame) combined with humid conditions. The smoke acted as condensation nuclei for the moisture resulting in thick heavy smog. Below is an extract from the public records office.

In 1954 the Committee on Air Pollution under the chairmanship of Sir Hugh Beaver reported after working for 21 months. In December 1952 London had suffered a serious smog problem resulting in 4000 deaths. The committee said that the problem of having clean air may take as long as 15 years to solve. Although the statistics were not fully available, they stated that there was a clear link between pollution and respiratory diseases. Whilst deaths in Denmark were as low as 2.2 per 100,000 men and 1.9 per 100,000 women, the figures in England and Wales were 107.9 for men and 62.7 for women in the year 1951. Following pressure in Parliament the government legislated for clean air.

Correlation between Deaths during the 1952 London smog episode and SO2 and particle concentrations

The Clean Air Act of 1956 resulted from this Committee’s work and smokeless zones were created that allowed only the use of smokeless fuel (see http://www.coalite.co.uk for information about smokeless fuel). This act has meant that this type of London smog has now been eliminated. SO2 levels – which were also high – did not immediately drop, but their impact on health was reduced, presumably because the particulates in smog help its delivery to the lungs. Subsequently, SO2 emissions have fallen significantly, owing to reduced domestic use of coal and the use of lower-sulphur coals.

The Environment Agency provides information about air quality trends with useful links: http://www.environment-agency.gov.uk/yourenv/eff/air/222825/222869/?lang=_e&theme=&region=&subject=&searchfor=

It is also the case that some aspects of this type of air pollution are natural. San Pedro’s Bay (LA) was named ‘The Bay of Smokes’ in 1542. The blue haze of The Blue Ridge Mountains of Virginia and The Blue Mountains in Australia is due to chemistry similar to that giving rise to Photochemical Smog.

Banjo players in the Blue Ridge Mountains

Photochemical Smog

Photochemical Smog is sometimes known as Los Angeles Smog, as this was where it was first identified. It has now been identified in many cities across the globe. What occurs during the day in a major city is illustrated in the figure.

What happens?

As the morning rush hour starts, NO begins to build up from exhaust emissions. At dawn, NO is converted to NO2 and as the day progresses, oxidants – mainly O3 – are generated. Peroxyacetyl nitrate (PAN), a powerful lchrymator is formed and the air beomes hazy as particulates are generated. At the same time oxidised compounds such as formaldehyde are formed and nitric and sulphuric acid concentrations increase.