Public Health (1991), 105, 217-228

© The Society of Public Health, 1991

Public Health versus Public Policy? An Appraisal of British Urban Transport Policy S. P. WolW and C. J. Gillham 2

1Toxicology Laboratory, Department of Clinical Pharmacology, University College London, 5 University Street. London WC1E 6J J, UK 2Department of Community Health and Nursing Studies, South Bank Polytechnic, Borough Road. London SE10AA

The most visible aspect of the relationship between transport and health is in the realm of road traffic accidents (RTAs). But the effects of transport policy upon the public health are much wider-ranging. They include exacerbation of social and health inequalities, separation from directly health-protective amenities and social isolation, as well as health damage by physico-chemical pollution. It is arguable that these factors may account for more years of life lost annually than do RTAs. The current focus on accident reduction as the sole means of avoiding adverse health effects of transport distracts attention from the wide health erosive effects of road traffic. Universal mobility and accessibility, independent of the car, is required for public health protection and advancement, since private transport carries many external, and poorly recognised health costs.

Car Ownership and Mobility Accessibility to employment, education, shops, recreation, social support networks, health services, and open space is important. ~People walk to such amenities, or need bicycle, bus, train or car. But walking and cycling are feasible only if the amenities are close to residences. In contrast, out-of-town retail developments, such as superstores and shopping malls modelled on N o r t h - A m e r i c a n establishments, have decreased local accessibility 2 as has the trend towards centralised health services, such as large, non-local hospitals and schools. It m a y be easy for car owners to reach a distant hospital or general practice (for purposes o f child immunisation or for some other aspect o f preventative medicine), but for those without a car a trip to the health facility m a y involve a gruelling ordeal, which might well not be undertaken. 2 Similar principles apply to nutrition. F r o m 1971-80 the n u m b e r o f retail outlets in the U K fell by 32%. 3 Surveys of the national diet show that although the diet has improved overall, the i m p r o v e m e n t has occurred overwhelmingly in the better-off. 4 The opening o f centralised, 'out-of-town' retail outlets aimed at the car owner, combined with the closure of smaller, local outlets m a y have the predictable consequence of poorer nutrition for those deprived o f cars and on limited budget. C o n s u m p t i o n of fruit and vegetables has decreased in the lowest income group, 4 and this observation might be related to the resurgence of vitamin C subnutrition in the U K , particularly in the elderly. 5 Those on lower incomes m a y well know what constitutes a healthy diet but appear to be often prevented from obtaining it for reasons o f accessibility. Whereas the car-owning individual can drive to the 'out-of-town' outlet to purchase a wide range of cheap food, the poorer, non-car owner is Correspondence: S. P. Wolff

218

S. P. Wolff and C. J. Gillham

restricted to the rapidly disappearing local shop, with its more limited, more expensive stocks. A 'healthy diet' obtained by the car owner might well cost less than the 'unhealthy' one available to the car-less disadvantaged. This is not a transitory problem. At present, 38% of all households in the U K do not have access to a car. The statistic for those households headed by a professional is 5% but for those headed by an unskilled manual worker it is 62% .6 When all who are capable hold driving licences (the 'capable-drivers saturation level') and possess, or have access, to cars then 35% of the population will still remain dependent upon drivers or public transport. This group consists of those under 17, perhaps half o f those over 65, those with disqualifying medical disorders, alcohol or drug problems, and those who simply find it difficult to drive] Air Pollution

Apart from these considerations of accessibility to health-protective amenities it is clear that public health may be affected directly by motorised traffic since this is the greatest single cause of air pollution) In addition to healthrdamaging noise, 9 m o t o r vehicles are the major source of carbon monoxide (CO), nitrogen oxides (NOx), aldehydes (RCHO) and hydrocarbons (HC). These may be directly health-damaging. NOx, R C H O and H C also contribute to the photochemical formation of ground level (tropospheric) ozone via a complex series o f chemical reactions. Controlled human exposures and field studies at encountered urban levels o f ozone have shown that ozone (even at levels below those laid down as permissible by the US Clean Air Act 1970, 120 parts per billion (120 p.p.b.)) causes transient and possibly, permanent lung function loss in children, adolescents and adults.~W~2 Seasonal fluctuations of ozone appear to have greater adverse impact upon lung function than do chronically elevated levels ~3but when ozone levels increase, so do hospital admissions for pulmonary distress. ~4These adverse effects are more evident in individuals with pre-existent lung conditions. ~5 CO is another potential toxicant. It has been described as a risk for individuals with cardiovascular insufficiency, as well as for foetuses, young children and individuals with haemoglobin abnormalities, such as persistent foetal haemoglobin. ~6 Most of the toxic effects of CO can be ascribed to its ability to bind 200 times more avidly to haemoglobin than oxygen, thus causing a diminished oxygen-carrying capacity o f the blood, but CO may also interfere with other processes by blocking other iron-proteins involved in respiration. ~7"~8 For example, low levels o f CO can diminish the ability o f the heart to recover from transient ischaemic episodes. 19 CO has also been proposed as a risk factor for atherosclerosis 2° and can impair cerebral function, 2~ particularly in individuals with coronary and cerebrovascular disease. 22 Levels of blood carbomonoxyhaemoglobin (COHb) as low as 2 - 3 % are known to interfere with cardiovascular function in individuals who already have a reduced capacity to deliver oxygen to the heart 2~-27but levels of C O H b as high as 5% have been found in non-smoking individuals in cars. 28 The omission of lead from petrol may well eliminate one potential source of hazard to the human health, but many remain. Benzene, present in petrol and also formed as a result of petrol combustion, has recently been implicated as a health hazard putatively responsible for 5000 cancer related deaths per annum in the UK. 29Occupational exposure to benzene at l - I 0 parts per million (p.p.m.) is certainly strongly linked with leukaemia (and less strongly with liver, lung and stomach cancer, as well as death from all causes 3°) but there is controversy about the carcinogenic potential of very low levels of benzene. 3t-33 Nevertheless, in the United States where 70% of benzene in the air is derived from m o t o r

Public Health versus Public Policy?

219

vehicles and refuelling, 34 there are an estimated 100-1000 leukaemia cases resulting from ambient benzene each year. 35 Urban air concentrations o f benzene in Europe can reach 50 p.p.b, and 1 p.p.m, can be reached in cars 36 so adverse effects might certainly be expected. For example, it has been proposed that non-occupational pre- and post-natal exposure to car-derived benzene might account for the leukaemia 'clusters' observed in 'New Towns' and geographically isolated industrial developments such as Sellafield? 7 A greater individual dose of the leukaemogen might be acquired in these areas o f greater car dependency. The 'clusters' might thus be the visible tips o f a much greater underlying problem. One study, for example, has shown that local neighbourhood traffic density is strongly correlated with childhood cancers, particularly leukaemia. 38 Diesel particulate is a risk factor for lung cancer 39 and contains polycyclic aromatic hydrocarbons which are mutagens and/or carcinogens. 4° In Sydney, it is estimated that 30 lung cancers arise each year as a result of traffic-derived benzopyrene, which is another product o f incomplete combustion. 41 Similarly, traffic-derived air pollution has contributed to the increase in lung cancers in Japan 42 and it is estimated that in the United States there are between 586 and 1650 new cancer cases resulting from air pollution each year, based upon the crude risk estimates for the small number o f identified combustion-derived carcinogens. 43 In addition to cancer, rates o f respiratory illnesses and symptoms are elevated among children living in cities with high motor vehicle-derived particle pollution 44 and total exposure to particulates correlates well with the incidence of chronic obstructive lung disease which is a risk for premature mortality, as Total mortality and morbidity from traffic-derived air pollution might thus be very high. Some estimates 46 place the individual risk of death (the annual number o f deaths from a specific cause as a proportion o f the total population) from car pollution in the United States as high as 1.67× 10 -4 (i.e. approximately two people per 10,000 die o f car pollution each year), which is almost twice as high as the individual risk o f death in road traffic accidents in the U K (see below). In California there have been a series of technological advances in vehicle exhaust controls, such as catalytic converters. Yet despite these steps, California's air quality has not improved (indeed worsened), since: (1) the number and length of car trips continue to increase; 47 and (2) 70% o f the hydrocarbons produced by the average Californian car trip are generated in the 'cold start' (the first mile o f travel before catalytic converters work efficiently) and 'hot soak' (evaporative emission after the engine is turned off) phases o f trips. 48 Efforts to improve traffic flows by increasing road traffic capacity have also resulted in more net air pollution by encouraging more driving. 49 Similar problems may occur in the U K where road traffic is projected to increase 83-142% by the year 2025. 50 Increased journey lengths inevitably also mean less reliance on walking, cycling and other less-polluting transport modes as well as decreased health-protective exercise for individuals 51 which may exacerbate pollution-driven health erosion. Increased commuting and congestion also cause higher psychological stress, more health complaints and g r e a t e r absenteeism due to illness, 52 as well as impacting upon the efficiency o f emergency and essential services. Pollution and congestion control efforts should thus focus on promoting mobility/accessibility without c a r u s e . 53

Accidents, Attitudes and Inequalities Motorised private transport also leads to accidents. Road traffic accidents (RTAs) are inevitable since cars are fast, heavy devices piloted by fallible individuals with a natural propensity to take risks on structures and in circumstances where there are many user conflicts. In 1988 5,041 people died in road accidents in Britain. In the same year, at least

220

S. P. Wolff and C. J. Gillham

311,473 were injured; 95,000 involved hospitalization. 54 Uncertainty exists about the true number of individuals injured each year, since injuries (including those which cause long term disability or hasten death) are under-reported 55 or inaccurately recorded. 56 For example, in one study it was observed that in a sample of 70 motorbike accident casualties, 49 were not known to the police (who are responsible for reporting injuries for inclusion in the statistics) and, o f those, 17 were serious as classified by Department of Transport criteria. 57 The under-reporting o f accidents involving vulnerable road-users such as bicyclists and pedestrians is probably much greater. 58 The health cost o f RTAs is high. Since many individuals who die in RTAs are young, each year, over the last five years, about 100,000 years of potential life have been lost as a result o f RTAs in the U K , compared with an estimated 50,000 from lung cancer and 200,000 from coronary heart disease. 59 The individual risk o f death in an R T A is 1.04 x 10 -4 for all ages, with peaks in the 15-19 (2.24 x 10 -4) and 80-84 (2.51 x 10 -4) age groups (Figure 1). 6° The individual risk o f death from an RTA is greater than the risk of death from illness (2.03 x 10 -4) in the former age group. 6° Concern about death and injury on the roads is expressed as efforts designed to improve road safety. This takes the form o f vehicle engineering changes to make them more 'crash-worthy' (such as car 'crumple' zones); the introduction of seat belt and drink-driving laws, speed restrictions and road engineering measures designed to minimise, or obviate, user conflicts. There is, however, controversy concerning the effectiveness of these measures in reducing RTAs, and certainly death and injury rates. Essentially, this controversy centres on the principles of 'risk homeostasis' and 'risk compensation'. 6~,62 According to the risk homeostasis theory everyone has a propensity to tolerate, or even seek, some level of risk and drivers are no exception; individuals adopt different levels o f risk-taking behaviour depending upon their perceived level of danger. If some external measure makes an individual feel safer (such as wearing a seat belt or advertised advances in braking systems), then that individual may behave more recklessly, and vice versa. 63 F o r example, when road conditions are perceived as very bad (snow and ice) then the numbers o f fatal accidents and the severity of accidents fall markedly, since drivers compensate by driving slowly and

Death

in r o a d t r a f f i c a c c i d e n t s

o x 200 >. 150

100

50 cm

0

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

~ / ¢o ,.,/~^." ,.,,/~/ ~b/ ~,.,/f~/ ~ / ~ /

Public health versus public policy? An appraisal of British urban transport policy.

The most visible aspect of the relationship between transport and health is in the realm of road traffic accidents (RTAs). But the effects of transpor...
939KB Sizes 0 Downloads 0 Views