Pollutant reductions in vehicular fuels do not necessarily result in clean healthy air: When lead was phased out of gasoline, other octane boosters were added. As a result, benzene, toluene and xylene -- all notorious bad actors --increased from 20% (1970s) to 32% - 40% by 1990. During the same period, gasoline volatility increased because of the addition of butane and other light-end components--and with increased volatility came increased emissions, especially during the summer.
Net result: Less lead, but increased emissions of unhealthy pollutants and smog precursors. From a health perspective, the risk to the public's neurological health from gasoline-borne lead leveled off (lead from past gasoline still persists in the environment). But different risks from the new formulation became more prevalent: benzene, toluene and xylene are carcinogenic, while smog adversely affects people with cardiovascular and respiratory conditions, among others.
The Clean Air Act as amended in 1990 includes mandates to reduce vehicle-related air pollutants by adding oxygenating compounds to gasoline. The first pollutant addressed was carbon monoxide (CO), with oxy-fuels mandated in some areas of the US at the start of winter 1992. Other air pollutants to be reduced were ozone precursors (including volatile organic compounds) in January 1995, and nitrogen oxides, beginning in the year 2000. The oxygenating compounds used to achieve these goals are methyl tertiary butyl ether (MTBE) derived from natural gas, and ethanol, derived from corn.
New additives, new health complaints
No health problems from MTBE or ethanol were anticipated, because both had been used in gasoline for years as octane boosters. The only difference was the increased level of the additives in the new oxy-fuels. MTBE levels increased to 15%, up from 0.2% - 9%, a difference that became important after the new fuels were introduced, because health complaints related to MTBE exposure began to surface almost at once.
They came, not from gasoline workers, but from consumers, who complained of headaches, dizziness, eye irritation and nausea. At first these complaints were thought to be attributable to the odd smell of the new gasoline, which might have given consumers the impression that they were getting higher exposures to gasoline than they actually were getting. EPA noted that "self-selected complaints ... are not useful to predict health risks, although they are invaluable in identifying the need for epidemiological or controlled studies."
MTBE had been tested for acute and chronic health effects under an earlier consent order. Based on this and later research, EPA set an inhalation reference concentration for MTBE that was intended to represent the concentration of MTBE that could be inhaled continuously over a lifetime by people (including sensitive people) without posing an appreciable non-cancer health hazard. Cancer data for MTBE indicated that, at least tentatively, a "possible human carcinogen" classification was "supportable" for MTBE. At the time of increased MTBE use, EPA regarded the cancer data to be "preliminary," but at the same time of questionable relevance to human health.
In the wake of the rising tide of health complaints associated with increased use of MTBE (and the related negative publicity), researchers investigated acute effects of MTBE further. By the end of 1993--a year after the oxy-fuels program took effect--EPA concluded that "the public are unlikely to experience the symptoms of interest (e.g.headache) after a 1 hour exposure to MTBE....However, these studies are limited in that they used MTBE in air [unmixed with either gasoline or other automotive emissions], and did not include representatives of subpopulations who might be more sensitive...." A small study conducted in this timeframe indicated that chemically-sensitive people and those who were ill "may tend to become more symptomatic with MTBE."
The economics -- and politics -- of fuel additives
Predictably, as the furor about MTBE and health grew, promoters of ethanol fuel additives tried to capitalize on their product's renewability, benign record-- and its identity as "not MTBE." Even though MTBE had had the lion's share of the fuel oxygenate market as the clean air fuel program began, the program's effect on ethanol demand increased the value of corn produced in the US by $1.3 to $2.1 billion in 1993. An EPA mandate for phased-in increases in the use of oxygenating compounds derived from renewable sources--like corn-- promised enhanced revenues for growers, processors and others involved in the ethanol additive industry. Elected officials from corn-producing states boosted ethanol as well -- sometimes at the expense of MTBE and its associated health effects reputation.
But did the additives actually improve air quality?
In 1993, EPA noted that the federal standard for carbon monoxide was met nationwide on all but two days of the first year of mandated oxy-fuel use. But University of Colorado researchers claimed that oxy-fuels weren't responsible for the pollution reduction, because CO levels were on the decline before the fuel change, primarily due to "fleet turnover" (the replacement of old vehicles with newer, cleaner ones). North Carolina's Department of Environment Health and Natural Resources agreed with the Colorado researchers that fleet turnover had already reduced CO in their state over time, and that adding MTBE to fuel did not make a significant contribution to further reductions. Despite such dissent, EPA continued to predict great reductions in pollution due to the oxy-fuel program as the 1995 phase, intended to address VOC emissions, was about to begin. In 1996, the National Research Council agreed with Colorado and North Carolina researchers, finding that MTBE "may not always reduce carbon monoxide emissions in cold weather," according to Environmental Science & Technology magazine.
Oxy-fuel use increases formaldehyde levels
All gasoline-fueled vehicles emit formaldehyde, a respiratory irritant and carcinogen. Vehicle emissions tests indicate that use of oxygenated fuels substantially increases such formaldehyde emissions--by 15% - 75% in one study, 18% in another. Atmospheric formaldehyde levels measured in Denver (an early site of oxy-fuel use) measured maximum four-hour formaldehyde concentrations as high as 50 parts per billion. EPA has noted that residents in homes in which formaldehyde measured as low as 0.06 milligrams per cubic meter of air reported dizziness, headache, apathy, inability to concentrate and sleep disorders. Note the similarity between these symptoms and those reported at the start of the first phase of the clean air fuels program. EPA also estimated in 1991 that 10% - 20 % of the US population may have hyperactive airways that make them more susceptible to formaldehyde's effects.
Health effects of oxy-fuels: questions persist
In August 1996, Environmental Health Perspectives, a journal of the National Institute of Environmental Health Sciences, published a letter from the Collegium Ramazzini, an international association of physicians and scientists concerned about occupational health. The letter said in part: "A major regulatory failure is that MTBE was not adequately tested for either acute or chronic toxic effects before it was added in significant quantities to gasoline. Many consumers and workers, when exposed to gasoline containing MTBE, complain of extreme headaches, vomiting, diarrhea, fever, cough, disorientation, dizziness, and skin and eye irritation."
The letter continued: "MTBE is known to cause central nervous system depression, tremor, ataxia, labored breathing, chronic inflammation of nasal mucosa, eye irritation, and skin rashes. MTBE may also increase risk of cancer, and this risk was not adequately assessed prior to introducing this product into commerce. The Collegium Ramazzini concludes that exposure to MTBE in gasoline should be avoided in order to prevent needless illnesses [in] both consumers and workers....It is not prudent to permit wide environmental releases of a compound that may cause acute illness as well as cancer."
Moreover, in its August 1996 report on MTBE, the National Research Council said that studies used by the US government to support use of MTBE suffer from "poor design, insufficient numbers of people, inadequate assessment of exposure, and subjective test results," and that "the government appeared to ignore data that consistently showed an increase in short-term health problems among workers exposed to MTBE on the job."
In September 1996, Chemical & Engineering News magazine reported that "it is still not known whether [oxygenated] gasoline or conventional gasoline is more harmful to public health and the environment.... Research is needed to characterize emissions from gasoline combustion, to assess exposure levels from these emissions, and to determine the effects of these emissions on human health, the environment, and on global climate change."
The story seems to have come full circle: In attempting to reduce one kind of pollution related to gasoline combustion, other pollutants have become problematic. Of course, combustion is inherently a pollution creating activity. Clean air regulations of automotive emissions may be destined to trade one set of problems for another, with only incremental progress in controlling pollutants that harm health.
-- Staff, The Human Ecologist
- post mortem in 1990 had subclinical lung damage. California Air Resources Board, 1996
- Damage to children's lungs from air pollution can impede lung development and may lead to chronic lung disease later in life. American Lung Association 1995
- 23.8 million children attend public schools with inadequate or unsatisfactory heating, ventilating and air conditioning systems. GAO 1995