Estrogens in coastal waters: the sewage source. (Science Selections).

Although estrogens are essential for successful reproduction in animals, various estrogen metabolites and by-products in treated sewage could have deleterious effects on marine organisms if ingested or absorbed. In this issue, Shannon Atkinson, now at the University of Alaska Fairbanks, and colleagues from the Hawaii Institute of Marine Biology report for the first time the distribution of sampled steroidal (nonplant-derived) estrogens in coastal waters of tropical oceans [EHP 111:531-535]. They found the highest concentrations near sources of sewage effluent.

Vertebrates excrete estrogens in the form of water-soluble polar conjugates. Synthetic steroidal estrogens excreted by humans include those found in birth control pills and hormone replacement therapies, which are among the most-prescribed pharmaceuticals in the United States. Lab experiments on sponges, crustaceans, mollusks, and echinoderms have shown a variety of harmful effects attributable to estrogens in varied forms and concentrations under a range of conditions. But it is not known how steroidal estrogens released into the environment affect growth, development, and reproduction of invertebrates, the foundation of marine food webs and ecosystems.

The researchers collected 129 water samples at 20 sites representing a range of coastal land uses and sewage inputs, from an arid, uninhabited coastline to a sewage treatment facility. Samples included both raw and treated sewage. One sample was taken from a completely contained, isolated coral reef ecosystem in the enclosed Biosphere 2 ocean in Arizona. All others were taken from Pacific, West Atlantic, and Caribbean coastal seas. Sampling locations ranged between 2 meters and 1 kilometer from shore, with most samples collected within 100 meters of shore.

Estrogens were concentrated by chromatography and assayed using a highly specific radioimmunoassay for estrone, a reduced form of estrogen. Concentrations of unconjugated estrone--which is generally more biologically active than conjugated estrone--ranged from undetectable (less than 40 picograms per liter [pg/L]) in the open ocean to nearly 2,000 pg/L in embayed areas near population centers. Estrone concentrations were highest near sources of sewage. Concentrations in embayed sites that received effluent were 1-2 orders of magnitude higher than in open ocean waters.

The lowest estrone concentrations were from open ocean samples taken in tropical regions near the Hawaiian Islands, the Marianas Islands, French Polynesia, and the Florida Keys, with averages of 15-52 pg/L. The sample from the Biosphere 2 ocean had the next lowest concentration (66 pg/L), indicating that high residence time of water over the reef community--in this case, eight years--does not necessarily create high concentrations of estrogen. The highest estrone values were from shallow embayments with known sewage inputs: Delaware's Rehoboth Bay (1,870 pg/L) and Key West Harbor (1,580 pg/L).

Effluent is not the only route through which excreted estrogens enter aquatic environments. In the researchers' experiments, estrogens filtered easily through gravel and sand, showing less than 20% adsorption, which indicates they can leach into the marine environments from septic fields and groundwater. Poorly flushed bays and lagoons known to receive sewage from septic fields and injection wells had built up estrogens to concentrations within a factor of 10 of those measured in sewage effluent.

Interestingly, unconjugated estrogens analyzed during one laboratory experiment were higher in a sewage sample (54%) than in two seawater samples (34% and 35%). One would expect higher concentrations of polar conjugates in treated effluent because its source is human waste, says Atkinson. The high percentage of unconjugated estrogens detected suggests that bacterial activity in the sewage may be converting the compounds back to a biologically active form.

About one-half to two-thirds of total estrone in the study samples occurred as polar conjugates. Although reef-building corals can take up significant amounts of unconjugated estrone from the water, it is not known whether corals or other organisms similarly can take up conjugated estrogens. Additionally, various aerobic and anaerobic bacteria could hydrolyze these esters under appropriate conditions, providing a possible continual source of unconjugated estrogens in the marine environment.

These data indicate that coastal environments may have large pools of environmentally persistent estrogens with unknown repercussions for nearshore ecosystems. This study provides quantitative baseline data from coastal waters, which will inform future studies of the effects of estrogens and estrogen mimics on marine organisms at naturally occurring concentrations. More thorough sampling is needed to establish fluxes of estrogens, possible uptake and accumulation, and physiological responses of marine organisms.