Organophosphate Esters in Drinking Water: Prevention and Removal
By Tim Rodgers | March 5, 2020
Organophosphate esters (OPEs) are some of the most commonly used flame retardants in consumer products today, especially electronics. OPE exposure has been linked to a number of different health effects, from reproductive problems to lower IQ in children.
OPEs are considered “additive” flame retardants, meaning that they are not chemically bound to the products in which they are placed but simply mixed in. This lack of bonding means that OPEs evaporate over time, entering the indoor air or attaching themselves to dust particles, which settle out onto all the surfaces in our homes and offices and our clothes.
Exposure to OPEs indoors comes mainly from two sources – air and dust, which our hands bring to our mouths when we eat or wipe our faces. This second pathway is particularly important for children, who typically consume a lot more dust when they are crawling around than the rest of us do! However, the chemical characteristics of OPEs means that exposure to certain OPEs can also occur through drinking water, although the story for that is a little more complicated.
Over time, indoor air and dust move outdoors through ventilation, laundry, or sweeping and vacuuming. Once in the outdoor air, rain washes the water-soluble OPEs from the atmosphere and into our lakes and rivers, where they are extremely persistent and also mobile – meaning that once in the water OPEs tend to stay there and can be transported long distances through rivers. These freshwater sources also receive water from wastewater treatment plants, where the same properties that make OPEs easy to wash out of the atmosphere and persistent in water also make them hard to remove from wastewater. These sources combine to give OPEs very high concentrations in surface water, especially in urban areas.
Where I am from in Canada, the same river has 30 wastewater treatment plants and 49 drinking water systems serving almost a million people. The release of OPEs and other chemicals to surface water there can have serious consequences if it is difficult to remove by drinking water treatment systems. This unfortunately is true for OPEs. Over time the multiple sources and difficulty in removing OPEs and other, similar compounds from water can lead to accumulation in drinking water cycles, which is a new source of concern for flame retardants. Some OPEs have been found in drinking water from around the world, indicating that this concern is warranted.
Today, researchers like me are working on ways to remove OPEs from wastewater, rain water, and drinking water through a variety of treatment technologies. This ranges from vegetated wetlands, where the plants might be able to absorb the OPEs before they are released to the environment, to advanced oxidation processes that aim to break the OPEs down wherever they might be found. These end-of-pipe solutions are important, but the most important way to reduce our exposure to OPEs is to support regulations to reduce the required levels of flame retardants in consumer products.
Tim Rodgers is a PhD Candidate at the University of Toronto in the Department of Chemical Engineering and Applied Chemistry