The days of river pollution causing fires are long over. These days Americans almost take it for granted that the rivers, streams and lakes around us are safe and clean. However, concerns about whether there are contaminants in water and their possible health risks still exist.
Numerous studies have documented the presence of various contaminants at very low levels in natural waters worldwide, but these studies don’t give us a complete picture. What’s known is only what researchers were specifically looking for, not all the contaminants that might be present, therefore giving us an incomplete conclusion about the possible health effects of the contaminants.
To examine this more closely, the U.S. Geological Survey (USGS) and the U.S. Environmental Protection Agency (EPA) recently conducted an in-depth study to provide more insight into the complex mixtures of contaminants present in U.S. streams.
In the first part of the study, the researchers studied water samples for 719 substances from 38 streams around the country. Perhaps not surprisingly, they found 406 of the substances in at least one stream. All of the water samples contained at least one of the substances and some contained as many as 162.
While bisphenol A (BPA) is frequently mentioned in media stories, researchers actually found very low levels in less than 40% of the streams. The levels were so low that a typical adult weighing 70 kg (154 pounds) would need to drink 21,472 liters (5,672 gallons) per day of water containing the maximum level of BPA (163 parts per trillion) just to reach the safe intake level for BPA set by EPA. That’s especially not likely to happen since the highest level was found in water from the Chicago Sanitary and Ship Channel, which is a primary pathway for sewage from Chicago to eventually reach the Mississippi River.
What’s more interesting is that a majority of the more commonly found contaminants are synthetic substances made to be biologically active (e.g., as pesticides or human drugs). And one of the top 10 in frequency of detection is estrone, which is a potent estrogenic hormone that is naturally produced in the human body.
The study’s authors didn’t indicate how the contaminants came to be in the water. However, some anecdotal evidence indicated that the samples with highest biological activity were collected downstream of wastewater treatment plants that contributed a significant amount of the streamflow.
BPA and many other materials can usually be found in wastewater and it’s well-known that BPA is readily biodegraded in today’s wastewater treatment facilities, which substantially reduces the amount of BPA released to the environment. Studies also show that other contaminants are not efficiently degraded in today’s treatment processes.
In the second part of the study, researchers focused on the biological activity of the water samples. They measured biological activity with four bioassays that measured estrogen, androgen and glucocortinoid activity. Estrogenic activity was found in all but one of the water samples but, as noted by the researchers, almost all of the activity could be explained by the presence of estrone.
Less than 1% of the estrogenic activity could be attributed to the presence of other estrogenic materials, and only a fraction of that can be attributed to BPA. The small amount of BPA is due to its low estrogenic potency, about 100,000 times less potent than estrone according to the researchers, and the low levels at which it is found. Taken together, the data suggest that the very low level of BPA found in some streams is not likely to be a health concern.
This new report concludes that more research is needed to further explain what contaminants are present in water and whether the mixtures pose any health risks. More importantly, the new data should help to focus further research and, eventually, help to prioritize actions to mitigate risks.
If you’re interested in this story, more blogs related to BPA are available at AmericanChemistry.com.