Damian E. Helbling, Cornell University http://helbling.research.engineering.cornell.edu

CornellEngineeringCivil and Environmental Engineering

Micropollutants in the Hu dson River Estuary What are micropollutants? We use the word “micropollutant” to describe man-made organic chemicals that are present in water and may include pesticides, pharmaceuticals, and industrial chemicals. “Micro” describes the fact that these chemicals are usually present at very low concentrations. “Pollutant” describes the fact that these chemicals are not of natural origin, though it is not intended to mean that they are inherently of concern. Some micropollutants might be present in groundwater, streams, rivers, ponds, or lakes. Some micropollutants might also be present in stormwater runoff, wastewater (sewage), or even drinking water. Typically, "micropollutants" does not refer to inorganic chemicals (i.e., metals, salts) or naturally occurring organic chemicals (i.e., algal toxins).

Where do micropollutants come from? Micropollutants come from human activities. For example, we use a variety of pesticides in agriculture. These chemicals can be transported from farms by means of spray drift, or in runoff following storm events. As another example, a variety of micropollutants are present in domestic or municipal wastewater. The pharmaceuticals we consume are often only partially absorbed by our bodies, and the remaining fraction is excreted with our waste. We also use a variety of personal care products, detergents, and other down-the-drain chemicals that are likewise transported with our wastewater to septic systems or sewage treatment plants. The processes used to treat our wastewater were not specifically designed to remove micropollutants; therefore some micropollutants may be discharged into the environment through treated sewage. Finally, a number of man-made organic chemicals are used by industry (e.g., PFOA) or for a variety of other useful applications; use and disposal of industrial chemicals may also result in their transport to the environment and occurrence in water resources.

How are micropollutants measured? Micropollutants are most frequently measured by means of “liquid chromatography mass spectrometry”, or LC-MS, which is a relatively new technology in the field of environmental science. The USGS published the first national reconnaissance of wastewater-derived micropollutants in 139 streams across the US in 2002. They reported concentrations of 82 micropollutants and concluded that concentrations rarely exceeded drinking-water guidelines; although they acknowledged that, in most cases, no such guidelines had been established for micropollutants. In 2017, the USGS reported concentrations of 406 micropollutants in 38 streams across the US and acknowledged a concern for the health of sensitive aquatic species even at low concentrations. Our study in the Hudson River revealed the presence of 168 micropollutants, including agriculture- and wastewater-derived micropollutants along with a variety of industrial chemicals. Measured concentrations agree with previous USGS studies, and other studies conducted around the world over the last 20 years.

Quick Facts • More than 84,000 organic chemicals are registered for use within the USA. • More than 1 billion pounds of pesti-cides are used for agricultural produc-tion within the USA each year. • Approximately 18 billion pounds of pharmaceuticals are consumed in the USA each year, with ~6 billion pounds excreted into wastewater. • Only 21 pesticides have maximum contaminant levels (MCLs) listed in the National Primary Drinking Water Stan-dards (NPDES); no pharmaceuticals have MCLs listed in the NPDES. • The US EPA issued a drinking water health advisory in 2016 stating that the combined concentration of PFOA and PFOS in drinking water should be <70 ppt. • In 2018, the NYS Drinking Water Council recommended limits of 10 ppt for PFOA and PFOS. NYS Department of Health will consider setting new MCLs based on that recommendation.

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What types of effects do micropollutants have on the environment?

Because there are so many different micropollutants, and so many aquatic organisms that may be exposed to micropollutants, it is difficult to assess toxicity and environmental health effects. In some cases, one could assume that micropollutants exert similar effects as their intended usage. For example, pesticides used to control the growth of weeds may inhibit photosynthesis in algae. A variety of more subtle or unexpected effects have also been suggested and explored. The situation is even more complicated when considering that many aquatic ecosystems are exposed to a mixture of micropollutants, not just one or two micropollutants, and there may be additive or synergistic health effects.

What types of effects do micropollutants have on human health? It is even more difficult to assess the human health effects of micropollutants. The mostlikely pathway by which humans can be exposed tomicropollutants is through drinking water. In a studyreported in 2018, the USGS examined tap water from UShouseholds for the presence of micropollutants. Seventy-five micropollutants were identified in at least one tap watersample, and some samples contained more than twentydifferent micropollutants at a cumulative concentrationexceeding 10 ppb. Data is still being collected andevaluated to assess the human health effects ofmicropollutants in drinking water. The uncertaintiessurrounding the human health effects ofmicropollutants motivate the development of bestmanagement practices that might limit human exposure tmicropollutants; these include eliminating upstreasources and developing new water treatment technologies.

Are micropollutants removed during drinking water treatment? Although essential for protecting public health from contaminants in source waters, conventional drinking water treatment plants are not spec-ifically designed or equipped to remove micropollutants. Studies have shown that some types of micropollutants can adsorb to flocs and other solid particles, but others may remain dissolved in water. Many organic chemicals react with chlorine disinfectants, but those reactions often lead to the formation of chlorinated byproducts and may not completely eliminate chemical risk. Therefore, it is possible that some micropollutants measured in the Hudson River are present in the finished tap water, though we did not study tap water in our study.

Are there technologies available to upgrade drinking water treatment plants? There are a few technologies that are available to upgrade existing drinking water treatment plants to remove micropollutants. Many municipalities in the US with high levels of PFOA and PFOS contamination in their source water have added activated carbon or ion exchange adsorption to their treatment trains. Activated carbon adsorption is also frequently used to remove pesticides from drinking water. Other utilities in the US or elsewhere in the world have adopted advanced oxidation processes or use ozone as a disinfectant to destroy certain types of micropollutants. Plant upgrades are most often motivated by new or emerging regulations or well-documented health risks associated with specific micropollutants. Alternative treatment technologies can then be evaluated for feasibility and costs to identify the solution that provides the greatest benefit to the communities served.

How can we prevent micropollutants from getting into the Hudson River in the first place? One goal of our study was to identify sources of micropollutants. Our study revealed that septic tanks and sewage treatment plant outfalls were major contributors of pharmaceuticals and other down-the-drain chemicals. Improving our understanding of micropollutant transport through leach fields and upgrading wastewater treatment infrastructure would likely reduce the load of micropollutants in the Hudson River. We also identified agricultural activities, particularly in the Mohawk River and Rondout/Wallkill watersheds, as a major contributor of micropollutants in the Hudson River. Establishment of best management practices for farmers may likewise minimize the transport of micropollutants from these sources into the Hudson River. Finally, industrial chemicals including PFOA are likely used at least sporadically throughout the Hudson River watershed; additional monitoring may reveal sources and explain varying concentration levels.

Hudson River Data at a Glance • We analyzed 127 samples collected in coll- aboration with Riverkeeper from 17 sites along the Hudson River from May 2016 - Oct 2017. • From our target list of 200 micropollutants, 168 were detected in at least one of the samples. • We classified the results as 116 wastewater- and 52 agricultural-derived micro-pollutants. • The micropollutants detected in all samples were atrazine (herbicide), gabapentin (antiepi-leptic), metolachlor (herbicide), and sucralose (artificial sweetener). • A majority of the micropollutants were mea-sured in the nanogram per liter (ppt) range, which is typical of concentrations measured in surface water systems around the world.

This work was prepared for the New York State Water Resources Institute and the New York State Department of Environmental Conservation Hudson River Estuary Program, with support from the New York State Environmental Protection Fund.

Damian E. Helbling, Cornell University http://helbling.research.engineering.cornell.edu/

Our study is available for download at: https://tinyurl.com/ybmcj6wr