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 the May 1 issue of ES&T (pp 1713–1719), 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 entering 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, 268A–269A). 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 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 the 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 a river, addition of such pollutants could also lead to the loss of 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, with very 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 growth was compared to 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-per-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, lowered the final yield of algae by 20% at concentrations 1000-fold higher (200 µg/L) in both uncontaminated upstream and polluted downstream samples when compared to 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. These 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 changing the algal community isn’t yet known. Smith says that the compounds could either be directly toxic or selectively interfering with some aspect of the algal biochemistry so that certain algae can no longer compete effectively for resources 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