Is rainwater drinkable?

A research paper written by scientists working at the University of Stockholm, Sweden, recently revealed that rainwater is not drinkable anywhere on the planet. This problem is due to contamination by a class of synthetic chemicals known to persist in the environment, so it is unlikely to go away.

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Find evidence of contaminated rainwater

The authors of the article published in the journal Environmental science and technology in 2022, discovered evidence of contamination of rainwater with chemicals classified as per- and polyfluoroalkyl (PFA) substances in samples from around the world.

PFAs are industrial chemicals widely used in packaging, shampoos and makeup until about two decades ago. Although largely eliminated from modern manufacturing, these toxic substances have been shown to remain intact in the environment for indefinite periods.

The researchers measured levels of PFA pollution commonly found in different environments around the world, including soil, surface water and rainwater. By comparing this data with the new indicative levels of PFA contamination that are considered safe by regulatory authorities, the researchers concluded that the rainwater is not safe to drink.

Extreme persistence of industrial chemicals in the environment

Researchers have been studying PFAs for a decade now and through field and lab work have found that although they were phased out by their main manufacturer (3M) 20 years ago, they are still present in the environment at similar levels.

PFAS, especially perfluoroalkyl acids (PFAA), are known for their high persistence. These acids can survive in their environment for a relatively long time.

With PFAAs, this high persistence rate can circulate through the hydrosphere continuously, even rising into the atmosphere on aerosol droplets from sea spray.

In addition to being highly chemically persistent, these substances are frequently cycled in the environment, leading to their ubiquitous spread across the globe. In a cycling process the team observed, PFAs rise from the sea into the sea air on sea spray aerosol droplets ready to be transported long distances and deposited with rain.

A changing regulatory landscape

Over the past two decades, new research linking PFAs to several health risks, including cancer, immune system problems, increased cholesterol, infertility, and pregnancy and birth complications. childbirth, have amended the regulations concerning these substances.

Notably, guideline values ​​for safe levels of PFAs in drinking water, surface water and soil have been significantly lowered in light of new evidence of their toxicity.

Due to this steady decline in safe contamination levels, PFA levels in rainwater, surface water and soil are above recommended levels worldwide.

In one example, the safe acceptable level of perfluorooctanoic acid PFA (PFOA) – now known to cause cancer – in drinking water has been reduced 37.5 million times in US guidelines.

While the regulatory environment has changed around PFAs, the health risks associated with them have always been present. While officially making rainwater and soil unsanitary around the world, current regulations better reflect the reality of PFA contamination and the risks it already poses.

Rainwater is not drinkable and is a global problem

Pervasively contaminated rainwater is a real problem worldwide. Environmental scientist Ian Cousins, a professor at Stockholm University and lead author of the paper, said:

“Although in the industrial world we do not often drink rainwater, many people around the world expect it to be safe to drink and to supply many of our drinking water sources. ”

But the pervasiveness of PFA contamination discovered in this research means that nowhere on Earth receives potable rainwater.

The team found that even in the most remote regions of the planet, such as Antarctica and the high plateau of Tibet, rainwater contains too many PFA particles to be considered drinkable, according to the latest guidelines. These extreme locations received rainwater with up to 14 times more PFA contamination than US guidelines consider safe, researchers said.

The irreversible effects of industrial chemicals

There are few opportunities to reverse the exposure of the planet’s environment to PFAs. The researchers argued that for this reason, the use and release of PFAs must be restricted urgently.

The authors of the paper argued that a boundary has now been crossed with PFA contamination in the environment; the effects of historical PFA pollution are likely irreversible.

The persistence and cyclability of PFAs, sometimes referred to as “eternal chemicals” because of these properties, means that substances in the hydrosphere and soil will stay there indefinitely.

While ambient levels of PFA measured in environmental samples have remained constant over the past two decades, levels detected in people’s bodies have dropped dramatically during this time.

Testing, filtering and purifying are essential measures that must be accompanied by committed and continuous investments.

References and further reading

AFP (2022) Rainwater unfit for consumption due to chemicals: study. [Online] Phys.org. Available at: https://phys.org/news/2022-08-rainwater-unsafe-due-chemicals.html (accessed August 15, 2022).

Cousins, IT, et al. (2022) Outside the safe operating space of a new planetary frontier for per- and polyfluoroalkyl substances (PFAS). Environmental science and technology. https://pubs.acs.org/doi/10.1021/acs.est.2c02765

Stockholm University (2022) It’s raining PFAS: even in Antarctica and on the Tibetan plateau, rainwater is unfit for consumption. [Online] SU.se. Available at: https://www.su.se/english/news/it-s-raining-pfas-even-in-antarctica-and-on-the-tibetan-plateau-rainwater-is-unsafe-to-drink -1.620735 (Accessed August 15, 2022).

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