A national reconnaissance for pharmaceuticals and other organic wastewater contaminants in the United States – II) Untreated drinking water sources

 

Q:  Why did USGS conduct this study?

A:  Part of the mission of the USGS is to assess the quality and quantity of the nation’s natural resources. The USGS Toxic Substances Hydrology Program conducts methods development and research on water quality, including new and understudied chemicals in the environment. The information we provide is used to evaluate the potential environmental and human-health significance of these “emerging contaminants.”  The emerging contaminants being studied have common domestic, commercial, and industrial uses and enter the environment via municipal, agricultural, and industrial wastewater pathways. Our first paper on emerging contaminants was published in 2002 and documented the occurrence of pharmaceuticals and other organic wastewater contaminants in streams across the U.S.  Since then we have published many more papers on this topic (http://toxics.usgs.gov/bib/bib-Emerging.html).

 

Q:  Why did you analyze for these 100 compounds?

A:  There are many chemicals used in our homes and workplaces which generally improve our quality of life. The chemicals we investigated have common pathways to the environment and therefore have the potential to be found in the same environmental settings. Having a good understanding of the types and mixtures of chemicals that occur in actual environmental settings is important to design and evaluate ecological- as well as human-health effects studies. When prioritizing chemicals for investigation we also consider available information on chemical use and the potential known or suspected health effects. It should be acknowledged however, that the information available for some compounds is limited.   Thus, another factor in targeting specific compounds is simply that some chemicals are readily measured by the laboratory techniques we have developed.    

 

Q: What are “untreated drinking-water sources?”

A:  Ground and surface waters in our aquifers and watersheds that are used for human consumption are known as drinking-water sources.   Our sample collection focused on sources of drinking water before it entered any drinking-water-treatment plant or was subjected to any drinking-water-treatment process.  Sometimes called “raw” water, these samples all represent untreated drinking-water sources.   This is not necessarily representative of the water you drink from your tap if your water is treated by public water systems and(or) home water-treatment devices.  However, analyses of untreated drinking water sources provide scientists and decision makers important data and insights on prevalence and magnitude of the targeted contaminants.

 

Q:  Does USGS develop laboratory methods to detect pharmaceuticals in water?

A:  Much of our research is devoted to developing analytical methods capable of detecting emerging contaminants including prescription and non-prescription drugs, antibiotics, hormones, personal-care products (such as fragrances) and other compounds associated with human and animal waste sources in the environment at sub part-per-billion to sub part-per-trillion levels.  This enables us to measure chemicals in water, soils, and plant and animal tissues at levels that help understand the processes that control their potential persistence in the environment and the circumstances where they may be a health concern.

 

Q:  How did you choose your sampling locations?

A:  This source-water reconnaissance was intended to identify a targeted subset of the potential chemicals that occur in sources of drinking water in aquifers and watersheds known, or suspected, to be impacted by human or animal wastes, as well as the mixtures and levels of chemicals present.  The reconnaissance sampling design targeted ground as well as surface waters used by populations ranging from one family to several million in as many states as possible.  Our final reconnaissance network consisted of 25 ground-water and 49 surface-water sites in 25 states and Puerto Rico.   Specific sampling locations were chosen in collaboration with local USGS experts in collaboration with water purveyors in order to represent the raw (untreated) water being used for drinking water to the extent possible.   Often samples were taken at intakes to drinking water treatment plants and raw-water sampling ports.

 

Q:  What did you find?

A:  As expected many of the targeted compounds were found in our water samples at low levels (parts per billion or less).  Sixty-three of the 100 targeted chemicals, including 4 naturally occurring plant and animal sterols, were detected in at least one water sample.  Maximum levels of all detected compounds were typically in the sub parts-per-billion range. Among the most frequently detected chemicals in surface water we found: cotinine (51%, nicotine metabolite), and 1,7-dimethylxanthine (27%, caffeine metabolite); and in ground water: carbamazepine (20%, pharmaceutical),  bisphenol-A (20%, plasticizer), 1,7-dimethylxanthine (16%, caffeine metabolite), and tri (2-chloroethyl) phosphate (12%, fire retardant).  Sixty percent of the 36 pharmaceuticals (including prescription drugs and antibiotics) analyzed were not detected in any water sample.

 

Q:  Were there any other important findings?

A:  A median of 4 compounds were detected per site indicating that the targeted chemicals generally occur in mixtures (commonly near detection levels) in the environment and likely originate from a variety of animal and human uses and waste sources.

 

Q:  How will results of this study be used?

A: These data will help prioritize and determine the need, if any, for future environmental and health-effects research for subsets of these chemicals and their degradates most likely to be found in water resources used for drinking water in the United States. The levels and mixtures of chemicals measured in this study will be used to design studies of potential ecological and human health effects so that they are representative of actual environmental conditions. However, we work very closely with USEPA as part of the process they implement for protecting public drinking water through the Safe Drinking Water Act. This process considers new chemicals and develops standards for chemicals in drinking water. USGS provides information to USEPA on the levels and mixtures of chemicals in ground water and surface water used for drinking water and in some cases on treated drinking water. We have and will continue to provide information on pharmaceuticals in the environment as part of this process.

 

Q:  What do these results tell us about the safety of our drinking water?

A:  This study was not designed to assess human-exposure pathways or human-health effects of these contaminants.  USGS does not conduct human-health research and we have no regulatory responsibility for it.  However, our results support a growing body of evidence that these, and similar, wastewater related chemicals are present in our aquifers and watersheds.   We work closely with other human-health agencies such as the USEPA and provide them with the scientific data and basis for sound policies and decisions regarding the safety of our pubic drinking waters.   On the other hand, there are an estimated 40 million Americans who supply their own drinking water through privately owned wells and springs and others who rely on commercially available bottled water for drinking.   Self-supplied drinking water sources are not regulated by the USEPA.  For more information on self-supplied drinking water you can talk to your local health department.  Additional information and related studies can be found on our USGS Human-Health webpage:  http://health.usgs.gov/   

 

 

Q:  As laboratory methods are refined and reporting levels are decreased do you anticipate different results if this study were conducted again?

A:  New laboratory methods presently in use or in development in our, and other, research laboratories will have lower detection levels than were possible in the present study.   Thus, we suspect that additional environmental occurrences of the targeted compounds below the detection levels used in this study will be detected in future studies. It is anticipated that repeated samplings at any site will have natural variations because of changes in hydrologic conditions and chemical use. In addition, new compounds (including specific active ingredients and/or their transformation products) will likely also be detected in our drinking-water sources.  

 

Q:  Can we get the data for any sites sampled in our state?

A:  All data will be publicly available on our website (coming soon) in a companion data report when the article is published officially in the journal.  It is important to note that this study was a national-scale snapshot of many source waters. These data are best used when aggregated.  Site-specific data may not be representative of the quality of individual drinking water sources. Such a local assessment would require a more robust sampling design including repeated sampling at each individual site.

 

 

Q:  When USGS studies drinking water supplies, how do you protect information relevant to the security of water supply facilities?

A: We maintain a policy that specific site-location information on drinking water intakes remains confidential for security reasons. We only provided information on the state, general location, and description of the water source (well or streamflow information). We did not publish specific purveyor names.  The strength of such broad national datasets is in the number of intake sites sampled across the nation, which describes the condition of source waters across the nation. An assessment of an individual purveyor or intake site would require repeated sampling of that site to get a reliable site-specific characterization.  

 

Q: Don’t some of these compounds occur naturally in the environment?

A: Yes, in fact a number of the targeted compounds occur naturally in the environment and therefore would be expected to occur in watersheds that are not affected by human influences. Consequently, the occurrence of these naturally occurring chemicals alone may not indicate a human- or animal-waste source.   On the other hand, some of these compounds are incorporated in various commercial products and by-products and(or) are biosynthesized in large-scale commercial applications and subsequently can become concentrated in human- and animal-waste source pathways to the environment. Closer inspection is required to identify naturally occurring chemicals that could indicate a human- or animal-waste-source pathway. The following table summarizes these naturally occurring compounds and their natural origin.