Emerging Threats - Pharmaceuticals Polluting Lakes and Rivers

The steadily increasing presence of pharmaceuticals in our water systems is sounding environmental warning bells. Although present in waste-water and Canadian rivers at levels of parts-per-billion or parts-per-trillion, pharmaceutical drugs are designed to be biologically active, and the potential effects of even very tiny amounts on non-target species, such as fish, are raising concerns.   

A few of these pharmaceutical drugs are endocrine disruptors – compounds that can affect reproduction and development.  One example is the synthetic estrogen found in birth control pills and excreted in the urine of women taking the pill.  A portion of synthetic estrogens can pass through waste-water treatment facilities and enter our rivers and lakes. An excess of estrogens (natural and synthetic) inhibits male fish sexual characteristics and can dramatically decrease fertilization success in exposed fish.  

As our human population continues to grow and age, the presence of pharmaceuticals will continue to increase in treated waste-water.  While it is neither feasible nor desirable to force the public to stop using pharmaceutical drugs – some, such as heart drugs, cholesterol-lowering drugs, and anti-epileptic drugs, are essential to health – it is important to investigate compounds that cause the greatest concern and assess methods to remove or reduce the amount of these entering the environment.

Dr. Joanne Parrott at the Canada Centre for Inland Waters in Burlington, Ontario, has spent the past several years conducting a variety of investigations, including fish life-cycle studies, into effects of pharmaceuticals on fish health. Her research has shown that when fathead minnows are grown from egg to adulthood in the presence of as little as three parts-per-trillion of synthetic estrogen (used in birth control pills), they are completely feminized. This means that all the genetically male fish express only female characteristics; thus no males are available to mate and to fertilize eggs. This amount of synthetic estrogen is equivalent to dropping a single birth control pill into 10,000 L of water.  A human female using the birth control pill will excrete this amount in her urine over the course of a single day.

Fat head minnows: male exposed to estrogen in the lab loses typical male characteristics expressed by normal or control male fish.

Dr. Parrott also examines impacts of effluents from sewage treatment plants on fish exposed for a full life-cycle to determine the effects of exposure to the complex mixture of pharmaceuticals and other compounds found in the environment, as opposed to exposure to individual compounds in the lab.  One study showed that exposure to municipal waste-water effluent caused egg production in minnows to drop by over 50 percent.

Dr. Parrott’s future goals for her pharmaceutical research include investigating the waste-water effluent “cocktail” of compounds further and prioritizing compounds based on their ability to have biological effects in fish.  The first step is to test compounds individually to ascertain what level is needed to cause problems in fish exposed for an entire life cycle; the next is to examine complex mixtures to determine the effects of the combined pharmaceutical mix.  This research will give policy makers the knowledge needed to make informed decisions about which compounds should be targeted for treatment and removal. This will help to reduce the amounts of the most harmful compounds entering our aquatic environment.

International Activities

Dr. Parrott represents Environment Canada on the Organisation for Economic Cooperation and Development (OECD) Committees for development and validation of fish tests for endocrine disrupting chemicals. She is a member of the European Union research group ERAPharm, and is conducting model risk assessments for human and veterinary pharmaceuticals. Dr. Parrott is the Water Science and Technology Directorate’s lead for pharmaceuticals in the environment. She is also a member of Canada’s Environmental Assessment Working Group, which will assess and recommend procedures for environmental risk assessment of pharmaceuticals, personal care products, and other compounds used in the Canadian marketplace.

Scott Unger, S&T Liaison