By Marguerite Huber
Approximately 1,800 drugs are approved for prescription use in the United States. Have you ever thought of what happens to all those drugs once they have left you (or your medicine cabinet)? Due to human excretion and people flushing unused pills, these pharmaceuticals can end up in the wastewater stream, presenting a challenge to the nation’s wastewater treatment plants.
To estimate potential pharmaceutical concentrations in wastewater, EPA scientists conducted a survey of wastewater effluent from 50 large U.S. municipal wastewater treatment plants between January and April 2011. They then used the data to evaluate an EPA model designed to estimate potential concentrations of active pharmaceuticals in treated wastewater.
The model generates preliminary estimates of associated risks, and provides a basis for prioritizing the pharmaceuticals that generate the greatest concern for future research efforts.
EPA scientists used pharmaceutical marketing data to choose the 56 pharmaceuticals with the highest number of minimum daily dose equivalents dispensed in the U.S. each year. You may recognize acetaminophen, ibuprofen, and hydrocortisone from the list.
The 50 wastewater treatment plants were chosen based on a number of factors, but together they produce about six billion gallons of treated wastewater a day that is released into rivers and streams. In all, these facilities serve more than 46 million people.
The researchers then analyzed treated wastewater samples from the selected plants to determine the concentrations of the 50 high-priority active pharmaceutical ingredients they identified from the marketing data.
Overall, the survey found low concentrations of pharmaceuticals present in every water sample the researchers analyzed.
Based on the screening data, the researchers estimated that risks were low for both healthy adults and aquatic life from pharmaceutical exposure in wastewater effluent for most drugs. They also found that even under the extreme scenario of someone consuming half a gallon of treated wastewater per day over the course of a year, they would get the equivalent of less than a daily dose of any pharmaceutical currently in use. For most pharmaceuticals, it would be less than one daily dose over the course of a lifetime.
Additionally, based on what the survey revealed about pharmaceuticals in wastewater effluent, the researchers determined that risk of antibiotic-resistant bacteria developing in aquatic environments is low.
Mitchell Kostich, an EPA Scientist who worked on the study, said Agency researchers plan to now focus on the handful of pharmaceuticals that are most frequently used, and appear at levels for which risks to aquatic life cannot be ruled out. With the help of the model and additional data, they expect to be able to predict the maximum wastewater concentrations of any pharmaceutical in current use.
Interested in more about this topic? Join our Water Research Webinar: Pharmaceutical Residues in Municipal Wastewater on Wednesday, September 24th from 12:00 PM – 1:00 PM (EDT), and check out our previous post, A Prescription for a Healthier Environment!
About the Author: Marguerite Huber is a Student Contractor with EPA’s Science Communications Team.