In the Lab

• Jul 01, 2003

All Washed Up? H₂-Fueled Car Leaks Could Hurt Ozone
Traditionally thought to be environmentally friendly because they only emit water vapor, new research shows leakage of the hydrogen gas that fuels hydrogen-fueled vehicles could actually cause problems for the upper atmosphere. In a June article in the journal Science, researchers from the California Institute of Technology report that if it accumulates, leaked hydrogen gas that would inevitably result from a hydrogen economy could indirectly cause as much as a 10 percent decrease in atmospheric ozone.

Researchers Tracey Tromp, physics research scientist; John Eiler, assistant professor of geochemistry; Yuk Yung, planetary science professor; Run-Lie Shia, planetary research scientist; and Mark Allen, Jet Propulsion Laboratory scientist, estimate that if hydrogen were to replace fossil fuel entirely, 60 to 120 trillion grams of hydrogen would be released each year into the atmosphere, assuming a 10 to 20 percent loss rate due to leakage. This is four to eight times as much hydrogen as is currently released into the atmosphere by human activity.

Because molecular hydrogen freely moves up and mixes with stratospheric air, the result would be the creation of additional water at high altitudes and a consequent increased dampening of the stratosphere. In turn, this would result in the cooling of the lower stratosphere and disturbance of ozone chemistry.

The estimates of potential damage to stratospheric ozone levels are based on an atmospheric modeling program that tests the various scenarios that might result, depending on how much hydrogen ends up in the atmosphere from all sources.

Ideally, a hydrogen fuel-cell vehicle has no environmental impact. Energy is produced by combining hydrogen with oxygen pulled from the atmosphere, and the tailpipe emits only water. The hydrogen fuel could come from a number of sources. Nuclear power could be used to generate the electricity needed to split water, and in principle, the electricity needed also could be derived from renewable sources such as solar or wind.

In comparison with the internal combustion engine that uses fossil fuels and produces many pollutants, including soot, noxious nitrogen and sulfur gases and carbon dioxide (CO₂), a hydrogen fuel-cell economy would almost certainly improve urban air quality.

Uncertainty remains about the atmospheric effects of the inevitable leakage of hydrogen from cars, production facilities and fuel transportation because scientists still have a limited understanding of the hydrogen cycle. This research indicates that leakage would be similar to the chlorofluorocarbons (CFCs), which leaked into the atmosphere and attacked the stratospheric ozone layer.

Unlike with the cases of CFCs, lead, methyl bromide and atmospheric CO₂, which were released into the environment long before their consequences were understood, the authors of the Science article say the current situation is unique in allowing society to understand the environmental impact well before the growth of a hydrogen economy. "We have an unprecedented opportunity this time to understand what we're getting into before we even switch to the new technology," said Tromp, the lead author. "It won't be like the case with the internal-combustion engine, when we started learning the effects of carbon dioxide decades later."

The question of whether or not hydrogen is bad for the environment depends on whether the planet has the ability to consume extra anthropogenic hydrogen, explains Eiler. "This man-made hydrogen will either be absorbed in the soil -- a process that is still poorly understood but likely free of environmental consequences -- or react with other compounds in the atmosphere."

Eiler said if soils absorb excess hydrogen, a hydrogen economy might have little effect on the environment; but if the excesses accumulate in the atmosphere, the stratospheric cooling and destruction of ozone modeled in the Science article are more likely to occur. Determining which process would dominate should be a solvable problem, he said.

"Understanding the effects of hydrogen on the environment now should help direct the technologies that will be the basis of a hydrogen economy," Tromp adds. "If hydrogen emissions present an environmental hazard, then recognizing that hazard now can help guide investments in technologies to favor designs that minimize leakage.

"On the other hand, if hydrogen is shown to be environmentally friendly in every respect, then designers could pursue the most cost-effective technologies and potentially save billions in needless safeguards."

If hydrogen indeed turns out to be bad for the ozone layer, Tromp and Eiler said they don't necessarily think the transition to hydrogen-fueled cars should be abandoned.

"If it's the best way to provide a new energy source for our needs, then we can, and probably should do it," Tromp said.

Eiler added, "If we had had perfect foreknowledge of the effects of carbon dioxide a hundred years ago, would we have abandoned the internal combustion engine? Probably not. But we might have begun the process of controlling CO₂ emissions earlier."

Estrogen Sends Adult Male Fish Fertility Downstream
Adult male fish fertility can drop by as much as 50 percent when exposed to short-term and low concentrations of synthetic estrogen, according to a study by scientists at the Department of Energy's Pacific Northwest National Laboratory (PNNL) and the University of Idaho that appears in the June issue of Environmental Toxicology and Chemistry.

Estrogen is an active ingredient in most oral contraceptives and often finds its way to surface waters through sewer systems. The PNNL study looked at the impact of a synthetic estrogen called ethynylestradiol, which is the chemical in oral contraceptives.

PNNL scientists from the lab's Marine Sciences Laboratory in Sequim, Wash., exposed adult male rainbow trout to three different concentrations of ethynylestradiol -- 10, 100 and 1,000 nanograms per liter of water -- for 62 days in a controlled laboratory experiment. The sperm of exposed fish were harvested then used in an in-vitro fertilization process with eggs from healthy female rainbow trout. A measurable decrease in fertilization was observed in the treated trout compared with a control group after 28 days.

In some experiments, a 50 percent decrease in sperm fertilization capacity was noted in semen collected from the trout exposed to 10 nanograms per liter of the estrogen, a level found in some surface water samples.

Irvin Schultz, PNNL toxicologist who led the study, and his colleagues studied the possible mechanisms for reduced fertility, specifically sperm motility and decreased hormone levels. While they were able to rule out sperm motility as the mechanism, their research revealed increased--not decreased--hormone levels in the blood plasma of fish exposed to 10 nanograms per liter of ethynylestradiol. However, hormone levels did decrease in fish exposed to the larger concentration of 100 nanograms of the estrogen.

Previous research reported that high concentrations of estrogen could change sex organs, causing juvenile male fish to develop female organs, but Schultz said this research reinforces that impacts aren't limited to juvenile fish.

"We can see that adult fish aren't immune to the effects of estrogen in waterways. Even short-term exposure to low levels of synthetic estrogen can impact their fertility," Schultz said. "Our results indicate that the fertility of a healthy male trout that has developed normally can still be affected, if that exposure takes place during a critical sexual maturation stage before spawning."

U. Michigan Races with the Sun
Hoping to extend its record as the most successful solar car team in history with a fourth victory in the American Solar Challenge, the University of Michigan Solar Car Team unveiled its new design for a solar-powered vehicle on May 23.

Named SpectruM, this year's car is part of a worldwide effort to highlight alternative energy sources and build vehicles that run solely on solar energy. It resembles a sleeker, larger version of last year's M-Pulse, the winner of the 2002 American Solar Challenge, with one major exception-- it's a two-seater. By taking on a passenger, new race rules allow cars to race with larger solar arrays. SpectruM and its passengers will weigh about 200 pounds more than the 600-pound M-Pulse and increase its solar array from 4,000 to 5,000 solar cells. The teams expects the car to have a top speed of 75 miles per hour and go from zero to 60 miles per hour in about 15 seconds with zero emissions. The driver and passenger will sit back-to-back with the passenger facing toward the rear.

The University of Michigan Solar Car Team is one of the largest, most complex and technically ambitious student projects at the university. About 150 students from the College of Engineering, Business School and School of Art & Design make contributions to the car. Throughout the year, the team not only designs, manufactures and tests the vehicle, but also is responsible for all aspects of fundraising, logistics and business functions.

This year's racing crew is completely new with an average member age of 20 years old. The team will compete against teams with varying levels of experience in the American Solar Car Challenge, a 2,200-mile, open-road race from Chicago to Los Angeles, in July. The team hopes to take SpectruM to the World Solar Challenge, a 1,800-mile race, in Australia in October. In the last cycle, Michigan's M-Pulse took third place in the Australian race.

Mercury could be slightly reducing the mental performance of millions of people worldwide, according to a study in Brazil. A release from New Scientist said while this study has been dismissed as too small to be conclusive, if it is right, levels of mercury currently regarded as safe for adults could impair brain function.

Low levels of mercury are already thought to damage the nervous systems of fetuses and babies, but the study of villagers in Brazil suggest that adults may be at risk too. A team of researchers led by Ellen Silbergeld from John Hopkins University in Baltimore studied 52 men and 77 women living in fishing villages downstream from gold mines. A lot of the mercury used to extract the gold ends up in rivers and fish. "They act almost literally as a sponge," Silbergeld said in the release.

To test the villagers' neurological abilities, researchers asked them, for instance, to remember a story and thread beads onto a piece of string. The researchers found that higher levels of methyl mercury in the villagers' hair--a measure of recent exposure--coincided with greater deficits in memory and motor skills (Environmental Health: A Global Access Science Source, vol. 2, paper 8, as cited in newscientist.com).

Mercury exposure levels among the villagers were not particularly high. Concentrations in the villagers' hair averaged 4 micrograms of mercury per gram of hair, just a tenth of the level the World Health Organization considers dangerous for adults.

But, according to the release, some researchers are dismissive of the team's findings. "Small studies are of no help at all," said Gary Myers at the University of Rochester Medical Center in New York, whose team recently added to the uncertainty by failing to find any adverse effects of methyl mercury exposure among children in the Seychelles. He maintains that only long-term studies can rule-out confounding factors.

Silbergeld said that while her study was small, it is the first to apply sensitive neurological tests to adults, and she believes it should justify larger studies.

This article originally appeared in the July/August 2003 issue of Environmental Protection, Vol. 14, No. 6.

This article originally appeared in the 07/01/2003 issue of Environmental Protection.