The motor car and public health: are we exhausting the environment?

THE CLASSIC DIVISIONS of environmental health by the vectors food, air and water lend themselves to studies of the causes of disease, but the best approach when looking for environmental health interventions is to focus on the organised areas of human activity that have the greatest impact on the environment — housing, employment, manufacturing and transport. Of all these, transport provides perhaps the greatest potential for health gain, at least in First World countries. The choices we make in transport bear directly on the health of the population. The most familiar risk to health in our car-dominant transport system is road-accident death and injury. In 1999, road accidents resulted in 509 deaths and 12 000 injuries in New Zealand, and, in Australia, 1759 deaths1 and an estimated 30 000 injuries requiring hospital treatment.2 About a third of the deaths occurred among children and adults under 25 years of age.1 In fact, these figures reflect recent declines in road accident fatalities in Australia and New Zealand, and one of the public health success stories of the second half of the 20th century. In both countries, fatality rates more than halved between 1970 and 2000. Road accidents are frequently attributed to speeding, carelessness and risk-taking, but changes in the behaviour of road users do not explain the drop in the road toll: more important factors have been better vehicle design (including seat belts), safer roads and fewer vulnerable road users (such as pedestrians, bicyclists and motorcyclists).3 By the standards of most OECD countries, however, our rates of roadaccident deaths and injuries are still high. In 1999, road deaths per 100 000 were 13.3 (NZ) and 9.3 (Australia), compared with 9.7 (Canada), 6.6 (Sweden) and 6.0 Britain).1 Furthermore, current patterns of industrialisation worldwide suggest that road accidents will become more prominent as a cause of death and injury. Already, more people are killed on the roads each year worldwide than die from malaria (2.3% v 1.9% of the global population).4 By 2020 road accidents are predicted to rank third among the causes of global disability-adjusted life-years lost, after cardiovascular disease and depression, and ahead of cancer. Road accidents are nevertheless just the tip of the transport and health iceberg. The effects of vehicle emissions on public health have been considerably under-rated. New data on the relation between exposure to fine airborne particles and mortality suggest that the burden of disease attributable to traffic pollution may be at least as great as that caused by road accidents. In Europe, the number of premature deaths among adults caused by vehicle emissions was estimated to be more than twice the number of deaths from road accidents, albeit with rather fewer years of life lost.5 Using the same approach, in New Zealand we have estimated that about 400 deaths per year can be attributed to traffic pollution.6 By comparison, about 960 deaths per year in Sydney in 1989–1993 have been attributed to exposure to particulate pollution from all sources.7 Not counted in these analyses are the effects of global air pollution as a result of vehicles, roadbuilding and fuel production. The transport sector is a major contributor to climate change. Transport emissions — already responsible for 28% of total greenhouse emissions in New Zealand8 and 16% in Australia9 — are increasing more rapidly in both countries than those from any other sector (see also the article by McMichael and Woodruff [page 590] on climate change and health10). Perhaps the most serious public health implication of our car-dependent societies is the unprecedented level of sedentariness that this lifestyle encourages. In cities, where the majority of Australians and New Zealanders now live, the proportion of trips made by walking, cycling or using public The motor car and public health: are we exhausting the environment?