The fact that oceans, rivers and other bodies have been terribly polluted by human activities is old news. But new research suggests that even rainwater across the world could be polluted by “per- and polyfluoroalkyl substances,” (PFAs) leaving them unfit for human consumption.
PFAs are hazardous man-made chemicals that spread globally in the atmosphere. They are used to make fluoropolymer coatings that can resist heat, oil, stains, grease and water. Products that use PFAs include clothing, furniture, adhesives, food packaging, non-stick cooking surfaces and electrical wire insulation.
As a result of their proliferation, they pollute even the most remote regions of Earth. During the last 20 years, new insights into the toxicity of these substances meant that the maximum acceptable guideline values for PFAs in water have decreased dramatically. According to a paper published in Environmental Science and Technology, this means that PFA levels in the rainwater are above these guideline levels all across the world. The study compared the levels of four PFAs, perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexanesulfonic acid (PFHxS), and perfluorononanoic acid (PFNA), in various global environmental media including rainwater, soils and surface waters.
Also Read |High salinity found in European river after fish die-off
While the research doesn’t include studies that took samples of rainwater in India, Ian Cousins, the lead author of a study told indianexpress.com that a similar conclusion can be drawn about the rainwater in the country.
“As we see rainwater levels worldwide are similar. I think the study can be extrapolated to India. PFAs are globally used and spread,” said Cousins, in an email interaction.
According to the United States Environmental Protection Agency, exposure to PFAs can cause a variety of health risks including decreased fertility, developmental effects in children, interference with body hormones, increased cholesterol levels and increased risks of some cancers, including prostate, kidney, and testicular cancers.
“Our knowledge of the toxicity of PFAS has increased over time. Recent research on immunotoxicity has driven the drinking water regulations even lower than before. Long-term low-level exposure to certain PFAS may make it more difficult for humans to build antibodies after being vaccinated again various diseases,” he added.
Also Read |Digging Deep: Deltas losing land due to rising sea levels and rivers changing course
This phenomenon is especially problematic in a country like India, with a long history of rainwater harvesting. In fact, some parts of the country have begun mandating rainwater harvesting. For example, the Tamil Nadu government directed all governmental, commercial, educational and residential complexes to set up state-approved rainwater harvesting structures on their building premises. As per the new study, the rainwater harvested in the country could be unfit for human consumption.
“There are fairly simple clean-up methods for removing PFAS such as filtering with activated carbon, but to clean the water to the very low levels in the guidelines is challenging and expensive. The activated carbon will need to be renewed regularly and the old contaminated material destroyed,” explained Cousins.
While the requirement for expensive filtration methods for rainwater is concerning in itself, there is an even bigger problem. Until recently, it was commonly believed that PFAs would eventually wash off into the oceans where they would be diluted. But the results of another recent study indicate that certain PFAs can be transported back into the atmosphere by being part of sea spray aerosols. This could mean that PFAs could be cycled through the hydrosphere constantly, leading to their continuing presence contaminating rainwater, freshwater bodies, and surface soils.