Issue link: https://hi.iaq.net/i/670243
Every breath we take: the lifelong impact of air pollution the levels of nitrogen oxides emitted by cars made in 1992, before catalytic converters were required. There have also been huge cuts in CO and hydrocarbons (VOCs) in petrol exhausts. In contrast to petrol engines, the technology applied to clean up diesel vehicles has not yielded significant improvements in emissions of nitrogen oxides, and the proportion of NO 2 in diesel exhaust has actually increased. 9 The types of fuel used to power road transport have changed over the past 20 years. Although heavy vehicles such as lorries and buses have always been powered by diesel, this was not the case for smaller vehicles that predominantly ran on petrol. In 2000, just 14% of new cars were diesel powered, but today this figure has risen to 50%, and almost all light goods vehicles and vans are now powered by diesel too. 10 This increase in diesel vehicles is very much a European phenomenon. Indeed, diesels play almost no role in car markets in the USA or Japan. Although diesel vehicles are marketed on their low carbon dioxide (CO 2 ) emissions, the Japanese car market has reduced CO 2 emission further and faster than Europe by investment in petrol engine technology. 11 The combination of an increased number of diesel vehicles and the technological difficulties in abating their real-world emissions has meant that urban concentrations of airborne particulate matter (PM) and NO 2 have not improved, as had been hoped. European limits for NO 2 were set in the late 1990s, to be met by 2010, but today busy roads in UK urban areas still fall a long way short of meeting these limits; in places, they are being exceeded by up to threefold. 12 In addition to arterial roads, the main problem areas are urban centres that are dominated by diesel vehicles; these include many shopping streets where traffic overwhelmingly comprises buses, delivery vans and taxis. Although tighter approval tests are expected to result in new diesel vehicles producing less pollution, it 6 © Royal College of Physicians 2016 Box 2: Better fuel can mean less pollution In the latter part of the 20th century, petrol was the main source of lead in urban air. Its use as a fuel additive peaked in the 1970s and 1980s. By this time, lead contamination in the environment had reached global proportions. Around the world analysis of ice sheets, lake and marine sediments and peat deposits showed increased concentrations compared with pre-industrial levels. 13 The Royal Commission on Environmental Pollution's 1983 report on lead in the environment 14 was a seminal moment in the recognition of the harm to the population arising from lead exposure. The commission called for a phased end to leaded petrol within 6 years. Today, lead is no longer used in petrol in the UK, but it is disappointing that the UK was one of the last countries in Europe to completely remove lead additive from fuel (in 1999). Since the reduction and eventual ban of its use as a petrol additive, there have been clear changes in lead in children's blood. This has decreased from concentrations in the 1970s that were considered harmful to fetuses and small children. 15 Many improvements have been made to oil-based fuels in recent decades. In addition to the phasing out of lead additives in petrol, the other major change has been the regulated decrease of sulphur in fuels, prompted by the need to control gaseous SO 2 and particulate sulphate pollution, and to enable catalysts and other exhaust-control technologies. The transition to ultra-low sulphur diesel in the UK in 2007 caused a decrease of 30–60% in particle number concentration, 16 a measure of airborne particles that had previously been linked to cardiac hospital admissions and deaths in London. 17 The decrease in the maximum allowed sulphur content in marine fuel in most European waters in 2006 caused a notable improvement in air quality, for example, in the Port of Dover. In Hong Kong, restriction on the sulphur content of heavy fuel oil in 1990 was associated with decreases in all-cause, cardiac and respiratory death rates (by 2–4%). 18