Environmental▼News Nitrate eyed as endocrine disrupter
LOUIS GUILLETTE/GUNNAR TOFT, UNIVERSITY OF FLORIDA
The nitrate in manure and fertilizer runoff is now under suspicion as a endocrine disrupter, according to new research from developmental endocrinologist Lou Guillette of the University of Florida. Although more work needs to be done to demonstrate cause and effect, scientists say the findings could have tremendous implications for water quality standards.
Studies of male alligators are pointing to nitrates as endocrine disruptors.
A retrospective study of seven Florida lakes shows that as nitratenitrogen concentrations in lake water rise above 10 parts per million (ppm), the limit for drinking water, testosterone levels in juvenile male alligators fall by 50% and the animals have smaller penises, Guillette told attendees at a water monitoring conference in Ames, Iowa, on Feb. 19. Guillette stumbled across the association between nitrate and depressed hormone expression when he found low levels of testosterone in alligators from eutrophic lakes with only traces of pesticides but high levels of nitrogen. The testosterone levels were similar to those of alligators inhabiting lakes with high levels of pesticide contamination. By analyzing the data statistically using linear regression, Guillette found a dramatic association between the low testosterone levels and high nitrogen concentrations in the water. “We know that exposure of young alligators to organochlorine pesticides can alter the
synthesis of hormones, but could nitrate in the environment continue to depress testosterone production?” Guillette warns that “these results are very preliminary, and we need to go out and measure concentrations of testosterone and nitrate in the blood and urine of individual alligators.” “Guillette’s results fit well with my studies showing that corticosterone and testosterone levels dropped by half in rats given 50 ppm sodium nitrate in their drinking water for four weeks,” says Nirmal Panesar, a steroid endocrinologist at the Chinese University of Hong Kong. He has also published research showing that exposure of testosterone-producing cells from mouse testes to nitrate shuts down their synthesis of testosterone. “These experiments show indirectly that mammalian cells can reduce nitrate to nitric oxide,” Panesar says. Nitric oxide acts as a hormone in the body, inhibiting hormone synthesis in the testis or causing vasodilation, he adds. For instance, nitric oxide action is the mechanism behind the anti-impotence drug, Viagara, but too much nitric oxide during early developmental stages appears to depress testosterone synthesis, which is necessary for normal development
of the penis, Guillette says. For a long time, scientists thought that nitric oxide in the body was only synthesized from the amino acid L-arginine. But in the mid-1990s, the cardiovascular literature began to include reports showing that mitochondria in the cell can reduce nitrate from food and water to nitric oxide, Guillette says. Nitric oxide is a potent inhibitor of cytochrome P-450, a key group of enzymes that help synthesize steroids, Panesar adds. “It appears that Guillette is seeing nitrate act as an endocrine disrupter, and if his research is published, it may intensify efforts to look at nitrate,” says Peter Weyer, associate director of the Center for Health Effects of Environmental Contamination at the University of Iowa. The nation’s waters are seriously contaminated with nitrate, and many Iowa streams report concentrations of 10–20 ppm nitratenitrogen, well above the level where Guillette is observing effects, he says. In fact, because Guillette’s preliminary work is finding an endocrine-disrupting effect of nitrate at levels around EPA’s nutrient criteria of 3.26 ppm nitrate-nitrogen, it may mean that nitrogen standards to protect wildlife and human health may have to be dropped even lower, adds Mary Skopec, research scientist with the Iowa Geological Survey. —JANET PELLEY
Common household chemicals affect algae In laboratory experiments, three common household chemicals have been found to reduce the diversity of algal communities at concentrations similar to those found for two of them in the environment. If these compounds have the same effect in freshwater streams receiving wastewater treatment plant (WWTP) effluents, they could alter the river’s food web and its ability to process potentially problematic contaminants. Moreover, because they are sensitive biotic communities, these effects on algae may be an “early warning” of future environmental problems. In this issue of ES&T (pp 1713–
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1719), researchers from the University of Kansas show that the antimicrobial agent triclosan, which is found in home products ranging from kitchen cleaners to toothpaste; the widely used antibiotic ciprofloxacin; and the surfactant tergitol NP10, which is found in hair dyes and most spermicidal lubricants, do not necessarily alter the total concentration of algae but rather which genera are present. There has been growing concern in both North America and Europe that pharmaceuticals and personal care products, such as these, are passing through WTTPs and enter-
Common household chemicals affect algae collected near the Olathe wastewater treatment plant on Cedar Creek River in Kansas. Inset shows a typical diatom from the river at 400x magnification.
News Briefs Wind keeps spinning up 2002 was another record year for wind power, with 6.8 gigawatts (GW) of new installations, according to the American Wind Energy Association (AWEA) and European Wind Energy Association (EWEA). Wind now supplies 0.4% of the world’s electricity demand. Most of the new turbines were erected in European Union nations, where the amount of wind-generated power jumped 33%. Germany has by far the greatest installed base of wind power, with Spain a distant second, and the United States close behind. India expanded its generating capacity by 13 GW last year and now ranks fifth in the world in installed turbines. For more information go to www.awea.org or www.ewea.org.
Economic slump aids emissions decline U.S. greenhouse gas emissions in 2001 dropped by 1.2% compared with 2000 emissions, according to the U.S. Energy Information Administration (EIA). The decrease marks the largest percentage annual decline in total greenhouse gas emissions from 1990 to 2001, according to EIA, which is part of the Energy Department. The decline is attributed to a combination of factors, including a reduction in overall economic growth from 3.8% in 2000 to 0.3% in 2001. U.S. emissions are nonetheless 11.9% higher than 1990 levels, but emissions have increased more slowly than primary energy consumption and gross domestic product. The report, Emissions of Greenhouse Gases in the United States 2001, can be found at ftp://ftp.eia.doe. gov/pub/oiaf/1605/cdrom/pdf/ ggrpt/057301.pdf.
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nutrients, the addition of toxic pollutants can lead to the extinction of sensitive species while concomitantly increasing the biomass of resistant species, says Smith. He draws that analogy of a lawn treated with an herbicide. In the extreme case, only a monoculture of grass would be left, but the lawn’s total biomass would be essentially unchanged. The result is less genetic diversity in the ecosystem. In rivers, addition of such pollutants could also mean the loss of a preferred or nutritionally better foods for organisms living on the algae, with a ripple effect all the way up the food chain. “[Rivers] could be left with a species-depauperate desert for consumers, containing few nutritionally adequate food items,” warns Smith. In this study, primarily conducted by Brittan Wilson in Smith’s group, algae growing in the Cedar Creek River were collected from both upstream and downstream sites of the Olathe WWTP in Kansas. Back in the laboratory, the algal cultures were spiked with one of the three target compounds, and their plant’s growth was compared with untreated algal suspensions. Wilson found that neither ciprofloxacin nor triclosan at the average concentrations found in U.S. streams by the USGS study (0.12 microgram-perBRITTAN WILSON; INSET: VALSMITH/W. DENTLER, UNIVERSITY OF KANSAS
ing streams. In a widely quoted study published last year, both triclosan and ciprofloxacin were found by U.S. Geological Survey (USGS) researchers in U.S. streams (Environ. Sci. Technol. 2002, 36, 1202–1211). “Many medicinal and pharmaceutical compounds are developed to exert an accurate effect on a specific organism during a well-defined period of time,” explains Alfredo Alder, with the Swiss Institute for Environmental Science and Technology. “But what happens in the environment, when these chemicals—albeit at a much lower concentration—act continuously on nontarget organisms?” Studies at the Universities of Guelph and Toronto have shown that high levels of a mixture of pharmaceuticals, including ciprofloxacin, affected organisms ranging from phytoplankton to sunfish (Environ. Sci. Technol. 2002, 36, 286A–287A). This new study investigated compounds separately and at concentrations closer to those found in the environment. “I use the terms ‘species turnover’ and ‘compensation’ to explain these findings,” says Val Smith, with the University of Kansas’s Department of Ecology and Evolutionary Biology and coauthor of the study. As species compete for light and
Environmental▼News liter [µg/L] and 0.15 µg/L, respectively) significantly altered algal biomass yields. In contrast, tergitol, which has not been measured to date in the environment, at concentrations 1000-fold higher (200 µg/L) was found to lower the final yield of algae by 20% in both uncontaminated upstream and polluted downstream samples when compared with untreated cultures. However, the key finding was that all three compounds caused significant changes in the composition of the algal genera. Moreover, there were signs that prolonged exposure to triclosan and tergitol had already led some algae taken from
downstream of the WWTP to adapt to these pollutants. In a second experiment, Wilson collected algae only from the upstream site and grew them in the presence of varying concentrations of triclosan, ciprofloxacin, or tergitol. She found that biodiversity, as measured in the number of different genera, gradually declined with higher concentrations of each of these compounds. The results are significant because they mark the first time that the ecological impact of chemicals contained in personal care products have been measured quantitatively. Why these chemicals are chang-
ing the algal community isn’t yet known. Smith says that the compounds could be either directly toxic or selectively interfere with some aspect of the biochemistry such that certain algae can no longer compete effectively in the ecosystem. Smith next plans to place containers with the compound of interest directly in the river, allowing algal growth at ambient temperatures, nutrient concentrations, and solar conditions. “I worry that the loss of biodiversity in the [WWTP effluent] receiving waters may reduce the river’s resistance to other stressors and its resiliency,” says Smith. —ORI SCHIPPER
Why do PBDE levels vary widely? reported in Europe for workers in electronics recycling facilities. However, the PBDE levels recorded in the milk of 67 British women by a team led by Kevin Jones of the University of Lancaster ranged from less than 1 ppb to 69 ppb. More than half of the women in the study had levels of 6 ppb or above. LEONA KANASKIE
It is becoming increasingly clear that North American women are taking up high levels of a relatively new persistent organic pollutant (POP), polybrominated diphenyl ethers (PBDEs), and new data out of the United Kingdom show that women there are accumulating more than their peers on the continent. As the evidence grows, many scientists studying the issue are observing that some people are taking up far more of the flame retardant chemicals than others. The latest data come from England and three different areas of the United States: California, Indiana, and Texas. Arnold Schecter, a professor of environmental sciences at the University of Texas at Houston’s School of Public Health, revealed one of the largest collections of U.S. data amassed to date at the Society of Toxicology meeting in March. The PBDE levels Schecter found are “strikingly high compared to Europe,” he says. He analyzed 47 samples of milk from women in Texas and looked for 13 different PBDE compounds, or congeners. The samples contained anywhere from 6.2 to 419 parts per billion (ppb) of the PBDEs per gram of milk fat. In comparison, Bert van Bavel of Örebro University in Sweden reports that the lowest level in Schecter’s sample is equal to the highest levels
Researchers suspect that old furniture may be responsible for some people’s high levels of PBDEs.
The PBDE levels of North Americans are 10 times higher than the (non-U.K.) European levels, and some North Americans have levels 10 times higher than their peers, summarizes Linda Birnbaum, director of the Experimental Toxicology Division of the U.S. EPA’s National Health and Environmental Effects Research Laboratory, who says that the range of the data that
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Schecter collected is roughly comparable with all of the data she has seen showing levels in North Americans (Environ. Sci. Technol. 2002, 36, 50A–52A). The European data also show that some individuals have significantly higher levels than their peers, van Bavel says. He routinely finds higher levels in 5% of the samples he analyzes from Sweden. The North American PBDE levels are notable for being orders of magnitude higher than human levels of dioxins in the parts-per-billion, rather than the parts-per-trillion levels, says Schecter, who has studied human exposure to dioxins. However, PBDE levels are generally an order of magnitude lower than those for polychlorinated biphenyls (PCBs), stresses Robert Hale, a professor in the Virginia Institute of Marine Science’s Department of Environmental & Aquatic Animal Health. The data on health effects from PBDEs are far from complete, but the chemicals are suspected endocrine disrupters, Birnbaum says. Rodent studies show that PBDEs may impair neurological functioning, and they appear to have additive effects with PCBs, she says. A new study out of Indiana University suggests that mothers may be transferring PBDEs to their babies in utero (Environ Health Perspect. 10.1289/ehp.6146). The researchers measured six different
