We rely on a variety of pharmaceuticals and personal care products, ranging from antibiotics and aspirin to shampoo and sunscreen, to make modern life more comfortable and convenient. But these substances, commonly called PPCPs, have lives that go on long after we use them. PPCPs enter our wastewater when they get washed down the drain or flushed down the toilet after passing through our bodies. After that, they end up back in the environment. But what does that mean for ecosystems and human health?
[Photo: Dr. Leslie Cizmas]
To answer that question, Texas A&M School of Public Health researchers first looked at previous studies on PPCPs and how they affect the environment, publishing a review article in the journal Environmental Chemical Letters. Antibiotics are an important subset of PPCPs, and the World Health Organization has identified antibiotic resistant bacteria and genes as the major health issue of the century. The research team also examined previous studies relating to treatment strategies for antibiotic resistant bacteria and antibiotic resistance genes, and published this review in Chemosphere.
The purpose of the first review was to establish what we know about PPCPs, where we need to know more and how to prioritize which compounds to look at. “We pulled together all of the research to give a starting point,” said Dr. Leslie Cizmas, assistant professor in the Department of Environmental and Occupational Health at the Texas A&M School of Public Health.
Much of the current concern on PPCPs is how they affect the environment. Research on the effects of PPCPs in algae has been key because algae are sensitive and can be tested quickly. Also, PPCPs can persist in the environment, and can affect various species, from algae up to large fish. Because of this, researchers also looked at studies on fish and other organisms. “We need to understand what’s going on at each trophic level,” said Dr. Cizmas.
In addition to these ecological concerns, there are potential human health issues related to PPCPs on the horizon. Population growth and increased reliance on water reuse, especially in drought-prone areas, could increase PPCP concentrations to a level where they start affecting humans as well. For example, some PPCPs could affect the toxicity of other PPCPs, making a mixture that is more toxic than either would be on their own. In addition, higher levels of antibiotics in wastewater could promote the spread of antibiotic resistant bacteria. “Further research will be needed to clarify this issue and point to antibiotics that should be saved for last line human use,” Cizmas said.
A major reason why PPCPs accumulate is that once they go down the drain, these substances tend to stick around.
“Wastewater treatment plants aren’t really designed to take these things out of the water,” Dr. Cizmas said. “PPCPs can pass through wastewater treatment plants into the environment largely untouched, and in some cases these compounds can react with disinfecting agents like chlorine to produce new substances that could be harmful.”
The exact toxicity mechanisms after release of PPCPs from wastewater treatment plants is the subject of one of the studies that Dr. Cizmas and her colleagues are undertaking after finding a starting point with their review article. This study is also looking at new methods that could remove them from wastewater. To be effective, removal methods will need to get rid of the most toxic and persistent compounds and be relatively inexpensive. Maintaining and upgrading wastewater infrastructure takes large amounts of money. “We need further research into cost-effective treatment methods, which is something we continue to look into,” said Dr. Cizmas.
The international interest in this research has brought several researchers from around the globe to the school. For example, a Fulbright scholar from the Czech Republic is currently studying the toxicity of various mixtures of antibiotics on algae and whether an iron-based disinfectant known as ferrate can reduce that toxicity. Virender Sharma, PhD, MTech, MSc, professor at the School of Public health and a pioneer in ferrate research, is working closely with the team of researchers.
Additional research will depend on prioritizing which PPCPs to focus on. Not all PPCPs are created equal, so researchers need to pay special attention to compound concentrations, toxicity and persistence, and how they interact with each other. This, in turn, will help policy makers decide where to focus their efforts, whether it’s upgraded wastewater infrastructure, or restrictions on how these substances are used.
These and other studies coming from the questions clarified by the initial review articles aim to better understand the complicated mixtures of PPCPs that are currently in our waterways, and seek to find ways to minimize any harm caused by these useful compounds. “Practical and applied research is going to be very helpful,” said Cizmas.