An unhealthy road Focus J. Environ. Monit., 1999, 1 23N With transport now the major source of many air pollutants, scientists need to fill in important gaps in our understanding of associated health risks. Few environmental issues pose such intractable problems as the growth of transport. Across both the developed and the developing worlds, demand for transportation in general, and motor vehicles, in particular, appears insatiable.In many countries, road transport is now the major source of many air pollutants and one of the main contributors of greenhouse gases. In the UK, for example, road traYc is set to increase by up to 50% over the next 20 years.1 Yet in 1995, road transport contributed 22% of national carbon dioxide emissions, up from 17% in 1985. For every 2000 litres of petrol (gasoline) consumed the average car produces: 4720 kg of carbon dioxide (CO2): 188 kg of carbon monoxide (CO); 28 kg of volatile organic compounds (VOCs); and 25.8 kg of nitrogen oxide (NO).2 A 10 mile (16 km) trip in light traYc lasting 11 minutes would produce 2 g of VOCs.2 The same trip in heavy traYc lasting 30 minutes would generate 7 g—a 250% increase in VOC emissions. Of course, we are all to blame.While we notice the deterioration in air quality, especially in cities, and empathise with the need to find more sustainable alternatives, few of us are actually prepared to give up our mobile cocoons. Instead we sit frustrated in traYc queues merrily pumping out pollution. Unpalatable options So what is to be done? Politicians have a variety of instruments at their disposal.Unfortunately, they are mostly expensive, long-term and not voterfriendly. Public transport, such as buses and trams, economic instruments, such as road pricing, and demand management schemes, such as carsharing, are all being muted. While these all have their part to play, experience shows that the incentives (or the sanctions) will have to be extreme to draw most of us away from our beloved cars.In the background, policy-makers always have an eye to the economic importance of the automotive industry. In the short-term, then, (the next 5–10 years at least), internal combustion engines (ICEs), and their associated emissions, will remain a key factor in the environmental equation. As engine technology has advanced, per unit emissions of major pollutants, such as CO2, CO and NO have decreased, mainly due to improvements in combustion eYciency.However, total reductions have been masked by dramatic increases in vehicle numbers and distances travelled. While these ‘traditional’ pollutants will continue to be important (particularly CO2 in the context of global warming), for the most part attention has shifted to other pollutants, such as particulates, VOCs and fuel additives, and their associated health eVects.Problem pollutants Particulates Particulate emissions are now generally measured in terms of PM10. These smaller particle sizes are considered the most representative both of vehicle emissions, and of those particles most likely to cause ill-health. With further advances, it is possible that measures based around even smaller particles (e.g.PM2.5) will become the norm. A high proportion of PM10 comprises fine particles that remain suspended for long periods.3 Concentrations vary seasonally, and are generally highest in the winter months. The variations are less than for other vehicle-related emissions, however, because during the summer months particulate sulfate and nitrate are also produced through photochemical oxidation.In contrast to gaseous pollutants, scientists have not been able to carry out controlled exposures for PM10 as a means of investigating health eVects.3 Thus, risk assessments have had to be based on epidemiological population studies. These pose several problems. Firstly, both particulate concentrations and general health patterns are known to be strongly related to the weather, so it is diYcult to distinguish cause and eVect. Secondly, in urban areas individuals’ exposures to PM10s can vary substantially, whereas air pollution measurements are generally intermittent and highly localised.Thus, the true eVects of low PM concentrations on individuals cannot be determined with confidence from population-based studies.Nevertheless, the evidence of linkages between PMs and human health is mounting. Reviewing the scientific literature, a UK expert panel noted recently that similar results had been found in cities across the world.3 The Panel found increasing evidence of a relationship between the magnitude of the eVect and the concentration of particles to which the population has been exposed.‘Such statistical associations’, they concluded, ‘increase the likelihood that the relationship is causal.’ The Panel also pointed to the lack of reliable evidence on threshold values for health eVects, and called for urgent research. If no threshold level exists then the theoretical basis for PM emission standards is undermined. Volatile organics Road transport is a significant source of VOC’s (also called air toxics), such as benzene, polynuclear aromatic hydrocarbons (PAH’s) and aldehydes.Benzene is a natural constituent of crude oil.2 It acts as an octane enhancer, preventing the fuel from igniting prematurely and causing engine damage. In motor vehicles, benzene arises in exhaust emissions and from evaporation during refuelling. 1,3-butadiene is found in vehicle exhausts.3 Over recent years, the higher olefins, from which it is derived, have been present in petrol in increasing quantities. It is partially removed by catalytic convertors. Many of these species are either suspected or known carcinogens, linked in particular to lymphomas and leukaemias.3 However, much of the24N J.Environ. Monit., 1999, 1 evidence on health eVects is based on a combination of laboratory studies and workplace exposures. Data on ambient exposures and associated health eVects is critically lacking. Fuel additives Following the phasing out of lead, which was used as a fuel additive for over 60 years, the oil industry has developed alternative means of improving fuel quality.2 Oxygenates are oxygen-containing compounds such as alcohols or ethers, which are blended with petrol in small amounts.As well as reducing emissions, some are used as ‘fuel extenders’, allowing other fuels, such as natural gas or biomass, to be added to the crude oil during petrol manufacture. The most common additive today is methyl tertiary butyl ether (MTBE), which is manufactured from a mixture of methanol and isobutylene.In the US, MTBE has been used in petrol since 1979 to reduce emissions of carbon monoxide and hydrocarbons. Despite its clean air benefits, concerns have grown about MTBE’s own environmental impacts, especially in the contamination of surface and groundwater. It is extremely persistent in water and may carry chemicals from petrol along with it into drinking water supplies.In 1998 the US EPA set up a ‘Blue Ribbon Panel’ to address these issues which will report later this year4 [see JEM, 1999, 1 (1) 10N]. EPA has also issued a research strategy, identifying key research and information needs relating to oxygenates in water.5 Topics covered include occurrence, source characterisation, transport, transformation, contaminant removal, exposure, aquatic toxicity and health eVects.To date, MTBE has received little attention in Europe. Denmark, traditionally in the vanguard of European environmental policy, adopted an action plan last year.6 As yet there is little evidence of other European countries following suit, or of action at EU level. Technology options The automotive industry is tackling the emissions issue across a broad front.On the one hand, measures such as engine design, mass reduction and telematics aim towards incremental improvements in fuel eYciency and emission levels. On the other hand, new propulsion systems, such as electric vehicles, fuel cells, LPG and various types of hybrids, aim towards the zeroemission or near-zero emission vehicle.Although steady progress is being made, and many of the advanced propulsion systems are at the demonstration stage, or beyond, future vehicle technology will be evolutionary, rather than revolutionary. Neither manufacturers nor consumers are enthusiastic about change. In any case, experience shows that technological advances are not always beneficial. For example, the widespread switch to diesel, during the early 90’s, is now widely seen as counterproductive.Although using 20–25% less fuel, new diesel vehicles emit 10–15 times more particulates than their petrol equivalents.7 Overall their emissions are estimated to be 3–4 times more carcinogenic. The health consequences of this increasing population of highly polluting diesel vehicles are as yet unknown.Emission benchmarks With limited penetration from other propulsion systems, future emission trends will continue to depend largely on ICE parameters. In particular, fuel eYciency, fuel quality and emission standards will be important benchmarks. Fuel eYciency Improvements in fuel eYciency as a result of technological advances have a knock-on eVect in terms of emissions. As cars burn less fuel, unit emissions of key pollutants also decrease.The European car industry has entered into a voluntary agreement under which CO2 emissions are to be cut by 25% by 2008.8 This will mean producing cars with average emissions of about 140 g km-1. The industry has also committed to commercial production of cars emitting 120 g km-1 during the period 2005–2010. Fuel standards Over recent years fuel has come to be considered with vehicle technology as a potential source of emission reductions.In the US this approach is embodied in the 1990 Clean Air Act, and in the EU in various directives on fuel quality. Under the latest directive, agreed last year, from 2000 sulfur limits in the EU will be set at 350 ppm for diesel and 150 ppm for petrol. Both limits will be tightened to 50 ppm in 2005.The directive also sets allowable levels of aromatics and benzene in 2000 and 2005. As well as fuel quality criteria, the US has promoted the use of reformulated (i.e. oxygenated) petrol and clean vehicle fleets. Starting in 1998, 30% of new vehicles purchased by centrally fuelled fleets in certain cities have been required to use reformulated fuels and to meet emission standards lower than those for other vehicles.The purchase requirement will grow to 70% by 2000. In June last year, more than 30 vehicle manufacturers from Europe, the US and Japan launched the ‘World Fuel Charter’ as the basis for future improvements in fuel quality.9 The Charter sets out fuel specifications and test methods for both petrol and diesel across three market categories.While a watershed in bringing together vehicle manufacturers worldwide, the Charter has not gone down well with the oil industry. It remains to be seen whether, and how soon, the two sides can reach agreement. Emission standards In the US emission standards have been tightened progressively under the so-called tier provisions of the Clean Air Act 1990.New standards for passenger cars and small trucks were fully phased in by 1996. All new vehicles now carry on-board diagnostic systems to alert drivers to malfunctions in emission control equipment. Many cities run mandatory inspection and maintenance programmes to check vehicle emissions on a regular basis. EPA is due to report later this year on whether even tighter standards are needed, technologically feasible and economical.Any further revisions would be introduced from 2004. In the EU, new emission standards were agreed last year that should reduce pollution emissions from new vehicles by up to 70% by 2005. From 2000 new cars will have to comply with their design emission limits for 80 000 km (or five years), rising to FocusJ. Environ.Monit., 1999, 1 25N crowded. As well as environmental regulators and NGOs, industries such as automotive, chemicals, and oil and gas all have an interest. Scientists have a key role to play in bringing together this broad spectrum of opinion, and even in brokering new relationships and partnerships. The breadth of the research issues, and their political and commercial sensitivity, calls for specialised research structures.In the US, the Health EVects Institute, which is funded jointly by government and industry, has contributed important findings on the health eVects of motor vehicle pollution across a variety of areas.10 A similar body is currently being proposed in Europe by ACEA, the European car makers’ association, and others. This, too, would be financed partly by industry and partly by the EU, with a remit to look at vehicle pollution in a European context.The European Commission has recently established its own facility, the Vehicle Emissions Laboratory (VELA), part of its Joint Research Centre, and as yet it is not clear how the two would work together. With research being undertaken worldwide, eVective communication and exchange of information are essential.For particulate research, the US EPA, the European Commission and the UK government have established a Global Information Exchange on Particulate Matter on the Internet.11 This model could be applied eVectively elsewhere. A Mobile Agenda At a technical level, research should focus around the three key pollutants. For particulates, the priorities include:- $ epidemiological and toxicological eVects of ambient particles; $ long-term exposure studies; $ evaluations of particle epidemiology; $ diesel exhaust emissions, including studies of carcinogenicity, eVects of new technologies on size distribution, and quantitative risk assessments.In VOC’s, key concerns include: $ epidemiology of benzene, 1,3-butadiene and aldehydes, to improve extrapolations from high doses to low doses and across species; $ development of biomarkers for use in epidemiological studies; $ extrapolation of health eVects to human populations at ambient exposure levels.Finally, fertile research themes in relation to oxygenates, such as MTBE, include: $ sources and environmental pathways of oxygenates; $ statistically relevant sampling of oxygenate exposures to determine human populations; $ epidemiology and toxicology of oxygenates; $ risk assessments for oxygenates which take account of the above data; $ health eVects of other fuel additives, such as methanol and MMT.Other areas where knowledge is lacking include: $ understanding of the eVects of longterm exposure to ozone; $ combined eVects of exposure to ozone and particles; $ studies of metal-containing additives, such as cerium, to diesel fuel References 1 ENDS Daily, 21/7/98, quoting the UK Sustainable Transport White Paper. 2 Exhaustion: A Guide to T ransportation Emissions, Environment Canada, 1998. Available at www.doe.ca/emission/ toce.html 3 Report of the Expert Panel on Air Quality Standards, The Stationery OYce, London, 1998.Available at www. environment.detr.gov.uk/airq/aqs/ 4 For details of the Panel’s work see www.epa.gov/oms/consumer/fuels/ oxypanel/blueribb.htm 5 Oxygenates in Water: Critical Information and Research Needs, EPA/600/R-98/048, Environmental Protection Agency, Washington D.C., 1998. Available at www.epa.gov/ncea/ oxywtr.htm 6 ENDS Daily, 2/2/98. 7 Based on recent work by the Swedish Environmental Protection Agency. 8 ACEA Press release 29/7/98. For details of the voluntary agreement see ACEA: www.acea.be 9 The Charter, containing detailed fuel specifications, is available at www.acea. be. The oil industry’s views are at www.europia.com 10 For an overview of the Institute’s work and related reports see www.healthe Vects.org 11 For details of the Global Information Exchange Program see www.epa.gov/ oms/interntl/pm/net.htm Mike Sharpe 100 000 km in 2005. On-board diagnostics to monitor emissions will also be mandatory on new petrolengine vehicles from 2000 and on diesel-engine vehicles from 2003.EU countries will be permitted to promote 2005-standard vehicles from 2000 through tax incentives. The legislation is based on the work of the Auto/Oil programme, an extensive technical co-operation between the European Commission and the oil and vehicle manufacturing industries, which is now entering its second phase. The Commission has indicated its intention to incorporate future vehicle emission standards into a unified framework covering all aspects of air quality policy [see p. 26N]. The road for monitoring Clearly, monitoring is central to an informed perspective on transport emissions.The gaps in our knowledge on health eVects are alarmingly large. Standards for fuels and emissions are evolving rapidly, but also diverging. As an increasingly wide range of actors are drawn into the debate, tensions are beginning to grow. All of this calls for a sound underpinning by the analytical sciences. The challenges for the monitoring community are three-fold:- (1) Inform risk assessment and regulation: Governments and industry are eager to apply risk assessment processes to transport emissions, technologies and fuels. Key data is needed to inform these evaluations. In particular, scientists need to address critical gaps in risk assessment for specific pollutants, such as PM10’s and certain VOC’s. (2) Track emerging technologies: With a whole variety of new technologies and fuels being considered, scientists have an important opportunity to lead the debate. Appropriate datasets will be needed to compare the public health risks between new and conventional approaches. For example, as with diesel or MTBE, a new fuel or technology may reduce some pollutants, but increase others or have other unforeseen eVects. Analysts should work with others to identify and assess emerging technologies as early as possible. (3) Build consensus: The vehicle emissions debate is increasingly Focus