Toxicity, emissions test results in for RFG

Contrary to reports in the popular press, a great deal of testing has been performed on MTBE.

Toxicological experiments show no ill effects, even at low levels of exposure. There are insufficient data, however, to draw the same conclusion for other ethers.

In addition, EPAs air-quality monitors reveal greatly reduced levels of most pollutants over the past 20 or so years. And results from the Auto/Oil Air Quality Improvement Research Program indicate that reformulated gasolines will further reduce many, although probably not all, automobile exhaust emissions.

Oxygenate toxicity

Toxicological testing of MTBE is much more extensive than many people realize. John Del Pup, manager of risk assessment and science policy for Texaco Inc. in Beacon, N.Y., described a number of the tests and surveys that have been performed to determine the health effects of oxygenates.

Oxygenates have been used to increase gasoline octane since the lead phase-out began. MTBE, specifically, was introduced about 15 years ago, says Del Pup.

Denver was one of the first cities to use gasoline containing MTBE on a widespread basis. During that time, 1988-1993, there was basically an absence of calls in to the health officials regarding concerns about MTBE in gasoline, said Del Pup.

This success probably is due to Denvers up-front program to introduce the product into the marketplace, says Del Pup, and to the availability of hot lines to answer consumer questions.

Testing

Surveys conducted by the American Petroleum Institute and Rutgers University simulated driver exposure during fill-up and driving. This level was determined to be about 1-1.5 ppm, compared to a current occupational exposure limit of 40 ppm.

(It should be noted that the 40 ppm exposure limit is a time-weighted average, assuming exposure of 8 hr/day, 5 days/week, and 30-year duration.)

The API/Rutgers study showed no significant impacts, said Del Pup.

Separate studies conducted in Albany, N.Y., and Stamford, Conn., indicated about the same level of consumer complaints of effects from gasoline. These results were surprising, and probably misleading, considering the marked differences between the two cities, in terms of both the number of gasoline grades containing MTBE, and the amount of MTBE in those gasolines.

Some symptoms are really related to the seasonthe flu season, and so forthand they kind of muddy up the works when you try to make a determination as to whether that, or some factor such as an oxygenate, is causing the problem, explains Del Pup. To rule out some of these nuances that affect study results, more controlled, laboratory tests were undertaken.

EPA and Yale University each conducted studies using MTBE concentrations of about 1.5 ppm during brief periods of exposure. Researchers conducting the Yale studies mimicked the volatile organic compound (VOC) content of gasoline and MTBE. The scientists examined viral vs. nonviral effects, in addition to mood alteration and neurotoxicity.

These studies showed no difference between exposed and nonexposed individuals.

In Sweden, a study exposed people to 180 mg/cu m (about 50 ppm) during exercise. Upon 1-hr exposure under conditions such as enhanced breathing rate, no effects were noted.

Epidemiological studies also have shown no problems for exposed individuals, said Del Pup.

A random telephone survey polled consumers in the Milwaukee, southern Wisconsin, and Chicago areas. Milwaukee is part of the RFG program, Chicago is in the oxygenated gasoline program, and southern Wisconsin uses conventional gasoline.

Despite these facts, the complaint levels were about the same in all three areas. This, says Del Pup, suggests culprits other than RFG.

In addition to all these favorable results, one ill effect has been reported for MTBE. Toxic Substances Control Act testing of MTBE resulted in kidney tumors in male rats only.

Male rats have been found, however, to produce a unique protein that makes them susceptible to certain components of wholly vaporized gasoline, which is used to conduct these studies. This isolated reaction is why gasoline is not considered a carcinogen by EPA, says Del Pup.

In other words, he explained, the science advisory board of the EPA made a determination that the male rat is not a predictor of human health.

Petroleum workers

Because the aforementioned results concern consumer exposure, occupational tests of MTBE are necessary to determine its effects fully.

API looked at 1,800 workers in the petroleum industry. No effects were found for short-term exposure (

Although these workers may experience short-lived periods of greater exposure, such as would occur in a splash accident, Del Pup points out that the geometric mean of the exposure data for petroleum workers is less than 1 ppm.

Another study involved garage workers in both northern New Jersey (in the New York City area, which uses RFG) and in southern New Jersey, where RFG is not required. No discernible differences were found between the two groups.

(Del Pup notes that, despite a number of consumer complaints registered in New Jersey, self-service is not available in that state.)

Oxygenate effects

Del Pup summarizes the exposure effects of MTBE as follows:

• Oralslightly toxic

• Dermalpractically nontoxic

• Inhalationpractically nontoxic

• Skinslightly irritating

• Eyesslightly irritating.

In addition, MTBE is not found to be a skin sensitizer (in other words, it does not induce a reaction).

While the data collected on MTBE are extensive, testing on other oxygenates such as TAME and ETBE is limited.

ARCO is funding testing of ETBE, and the EPA and manufacturers of TAME are planning studies of that product. In addition, the Oxygenated Fuels Association is delving into deeper MTBE studies.

All these studies are being conducted at the Chemical Industry Institute of Toxicology. The purpose of the tests is to acquire a data set robust enough to draw conclusions about oxygenates other than MTBE.

These shorter-term, pharmacokinetic studies determine how the body takes in, metabolizes, and excretes the material being tested. If a minimum data set can be determined to project the potential effects of the other ethers, the more expensive, longer-term studies already done on MTBE can be considered valid for ETBE and TAME.

Future

Testing to date has focused on MTBE alone, rather than on MTBE as a component of gasoline. Del Pup says tests of the effects of automobile emissions on health, called 211-B tests, will determine fuel interactions.

The EPA would like to jump from the 211-B tests, now in preparation, to what is called Tier 3 testing, said Del Pup. These tests will look at the combination of oxygenates and gasoline.

In summary, Del Pup said that the independent studies conducted on MTBE have all confirmed the safety of the product.

So far,...based upon the human clinical studies...[and] the animal studies, we can confirm that, at this point in time, methyl tertiary butyl ether is certainly safe for use in gasoline.

Air quality

U.S. air quality has improved dramatically over the past 20 years, according to Mitch Baer, a senior regulatory analyst at the American Petroleum Institute.

U.S. emissions of carbon monoxide, VOCs, and lead have decreased significantly since they peaked in about 1970. Nitrogen oxides (NOx), on the other hand, have increased steadily since the beginning of the century, but have generally leveled off since 1970.

Emissions of particulate matter have decreased significantly since 1940. And sulfur dioxide emissions have generally fallen since the late 1970s. Those emissions will continue to decrease steadily, says Baer, because of the acid rain provisions of the Clean Air Act.

In addition to emissions data, EPA also tracks air concentrations of these pollutants. Atmospheric pollutant levels have been decreasing steadily in recent years.

Ozone

EPA is under court-ordered deadlines to review the National Ambient Air Quality Standards (Naaqs) for three pollutants: ozone, SO2, and particulate matter smaller than 10 m, known as PM10.

The formal rule-making process for the ozone changes will begin this month and, in 1997, EPA will make a final decision about whether to revise the federal ozone standard, said Baer.

The current Naaqs standard for ozone is 0.12 ppm during a 1-hr period. Fig. 1 (55490 bytes) is a map of U.S. ozone nonattainment areas using this standard as a basis.

As a result of EPAs review process of this 1-hr, 0.12-ppm maximum, the agency is considering reducing the ozone standard. Baer says EPA is leaning toward an 8-hr, 0.08-ppm maximum.

Converting this standard to a 1-hr value for comparison purposes is difficult because of meteorological considerations. But Baer says is it is approximately equivalent to a 0.095-0.10 ppm limit, as measured over 1 hr.

As can be seen in Fig. 2 (79618 bytes), this tougher standard would greatly increase both the number of areas designated out of attainment with Naaqs standards for ozone, and the size of those areas. In fact, says Baer, the area considered nonattainment in this map is 3-5 times larger than that in Fig. 1 (55490 bytes), which is based on current Naaqs standards.

The lower NOx...will lead to more and expanded control strategies and technologies that will be thrown at stationary sources, mobile sources, and consumer products, predicts Baer. Eventually, he said, its all going to lead back to fuels.

Overall demand for fuel will likely decrease as a result of these tighter ozone standards. Demand for RFG-type fuels, however, will probably increase.

The reality of how areas come into compliance isnt a nice, smooth line, said Baer. It tends to be a broken line that goes up and down.

As you get closer to the standard, that line tends to jump up and down fairly frequently, because meteorology tends to play a very big role in whether youre going to be in nonattainment or attainment status of the ozone standard.

As a result, API is asking EPA to consider a so-called too close to call standard for ozone. Using this method of determination, when an area comes within an error band around that standard, the areas implementation programs affecting stationary and mobile sources and consumer products are frozen.

This allows those strategies and technologies to take hold and actually bring you to a soft landing slightly under the standard, Baer explained.

Historically, EPA has required application of even more, stricter controls as an area approaches a Naaqs standard. But, says Baer, EPA appears to be seriously considering the proposed too close to call designation.

API also is asking EPA to consider what it calls a population weighted exposure metric for determining ozone exposure levels. This measure, in units of people-ppm-hr, relates the number people exposed to the level of exposure.

API believes this is a better measure of health effects than the EPAs current method. The protection of a monitor from high ozone is not the same as the protection of people from high ozone, said Baer, referring to the fact that many monitors are located in areas of extraneously high ozone concentration.

SO2, PM10

A proposed rule for the revised SO2 standard was published in 1994. Among the options being considered are:

• A 5-min standard of less than 1 ppm

• Increased enforcement of the current 3-hr standard, with emphasis on 5-min peaks.

  Baer says the effects of the options under consideration will be:

• Shorter-term standards

• Lower-sulfur fuels

• Stricter controls on processes burning fuels containing SO2.

The proposed rule-making for PM10 (particulate matter smaller than 10 m) is due by June 30, 1996, with final action required by Jan. 31, 1997. APIs best guess regarding this standard is that it will use a 2.5 m cut point rather than 10 m, says Baer, making the standard a PM2.5.

The numerical value of a 2.5 m standard would be 50-70 mg/cu m, said Baer, compared to 150 mg/cu m for the current standard.

Baer predicts the following possible impacts of the options under consideration for particulate matter:

• Reduction in diesel fuel use

• Increase in control technologies and strategies applied to facilities

• Marked increase in number and size of nonattainment areas.

One aspect of the whole ambient-standard setting process is that the agency does not consider economic impacts or economic considerations as it sets those standards, said Baer. Its not allowed to.

What this means is that the agency can only look at health effects, he added. APIs calculations show that the costs of achieving the new ozone standard, for example, will be staggering.

Redesignation process

In 1991, 98 areas were designated as nonattainment for at least one pollutant regulated under the Naaqs (Fig. 3 [23686 bytes]). By 1995, the number of nonattainment areas had fallen to 77.

Twenty-eight other areas have petitioned EPA for attainment status changes. But because of a number of exceedances in those areas during the summer of 1995, many of them will have to withdraw their applications for redesignation.

The EPA requires an area to clear very high hurdles to achieve attainment status, says Baer. He characterizes the redesignation process as working very, very slowly.

Emissions

Michael Ingham, co-chairman of the joint Auto/Oil Air Quality Improvement Research Program, says the Auto/Oil program has conducted three experiments studying low-level oxygenate blends in gasoline and the impact of oxygenates on exhaust emissions.

These three studies were:

• The AMOT study, which sought to determine whether 90% distillation point and concentrations of MTBE, aromatics, and olefins affect automobile emissions

• The Rvp/oxygenate study, which sought to separate the impacts of these factors on exhaust emissions

• A third study that examined the benefits of MTBE in a CARB Phase 2 gasoline, including the effects of vehicle technology.

AMOT

The AMOT study looked at parametric variations of T90 and compositional parameters said Ingham. Aromatics were varied from 20 to 45 vol %, MTBE from 0 to 15 vol %, and olefins from 5 to 20 vol %. The 90% point was varied from 280 F. to 360 F.

In this study, 16 fuels (8 containing oxygenates and 8 without) were tested in two types of cars: one called the current fleet, comprising 1989 model-year vehicles, and the other, an older fleet.

Fig. 4 (27918 bytes) shows the effects of 15 vol % MTBE on emissions of hydrocarbons (HC), non-methane hydrocarbons (NMHC), carbon monoxide (CO), and NOx. NMHC represents the reactive portion of the organic material in the gasoline, said Ingham.

In this figure, the bars represent 95% confidence intervals around the average response recorded.

The largest effect of 15 vol % MTBE was on carbon monoxide emissions. In the current and older fleets, reductions in CO emission were, respectively, about 11% and 15%, according to Ingham.

Neither fleet saw a statistically significant change in NOx emissions as a result of adding 15% MTBE to the gasoline. And the effects on HC and NMHC emissions were about equal.

AMOT tests of the interactive effects of aromatics in MTBE blends showed no statistically significant increase in NOx emissions in a blend containing 45 vol % aromatics. But a 20%-aromatics blend increased NOx emissions by about 5%.

This effect is significant because CARB RFG is a low-aromatics fuel, and federal Phase 2 RFG is likely to have a low aromatics specification as well.

The AMOT study also studied the effects of MTBE on emissions of toxics:

• Benzene emissions were reduced slightly in the current fleet and about 10% in the older fleet.

• 1,3-Butadiene emissions were reduced about 9% in the current fleet, with no change in the older fleet.

• Formaldehyde emissions increased by about 25% in the current fleet and about 20% in the older fleets.

• Acetaldehyde emissions did not change significantly in either fleet.

Rvp study

In this study, the current fleet was used to test four base gasolines for the interactive effects of Rvp and oxygenates. The gasolines comprised:

• Fuel A, containing an industry-average 32 vol % aromatics

• Fuel F, a highly reformulated fuel similar to California Phase 2 gasoline, containing 20% aromatics, 4% olefins, and low T90.

• Fuels V and S were debutanized versions of, respectively, Fuels A and F, designed to decrease Rvp about 1 psi in each fuel.

These four base fuels were used to make several oxygenate blends.

Fig. 5 (43334 bytes) shows the effects of oxygenate type on HC, CO, and NOx emissions. Based on the results of this experiment, says Ingham, oxygenate type does not appear to make a significant difference. The results were, in fact, similar to those shown in Fig. 4 (27918 bytes).

Fig. 6 (26832 bytes) shows the effects of aromatics on NOx, for both low-Rvp and high-Rvp fuels.

The NOx response in the higher-aromatics fuels was indistinguishable from the base gasolines. In the lower aromatics fuels, however, the addition of oxygenate produced about a 10% increase in NOx emissions, said Ingham.

The effects of oxygenate type on toxics emissions were also studied in the Rvp/oxygenates experiment. Table 1 (13466 bytes) shows that ethanol, MTBE, and ETBE all reduced emissions of benzene and butadiene.

The effects on the two aldehydes, however, were mixed. The addition of ethanol increased formaldehyde emissions directionally, although not to a statistically significant extent.

The marked increases in acetaldehyde emissions are not surprising from a chemistry standpoint, said Ingham, but it should be noted that baseline acetaldehyde emissions are very low.

Study comparison

Ingham says the results of the AMOT and Rvp/oxygenate studies are pretty consistent.

The addition of oxygenates tends to reduce hydrocarbon and CO emissions, while the effects on NOx emissions were a mixed bag. In addition, emissions of benzene and butadiene were directionally decreased in all three of the Auto/Oil experiments.

In the third Auto/Oil study, the two fleets tested showed about a 5% reduction in both HC and NMHC, and about a 10% reduction in CO. Neither of these results are statistically significant, said Ingham, but it should be noted that this experiment was quite a bit smaller than the other two.

The magnitude and direction of the results, however, were similar to those seen in the earlier experiments. NOx also increased directionally.

Ingham summarizes the results of this third test as follows: For the Tier 1 and advanced technology fleets, the response to the addition of 11 vol % MTBE is almost nonexistent.

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