by Andrew MacFarlane, originally published on April 13, 2016

Although smog may be the first thought that comes to mind when diagnosing China’s pollution problem, it’s the country’s water supply that poses the biggest threat to the nearly 1.5 billion people who live in the world’s most populous country.

Over 80 percent of the water used by homes, farms and factories across the country’s plains is too contaminated to drink or bathe in, according to a new report by Chinese Media.

“From my point of view, this shows how water is the biggest environmental issue in China,” Dabo Guan, a University of East Anglia in Britain professor, told the New York Times.

“People in the cities, they see air pollution every day, so it creates huge pressure from the public. But in the cities, people don’t see how bad the water pollution is. They don’t have the same sense.”

A large number of Chinese cities get their water from deep reservoirs, which weren’t part of the studied wells, said Ma Jun, head of the Institute of Public and Environmental Affairs in Beijing, in a Chinese news release.

In the survey conducted by the Ministry of Water Resources, water was classified into five categories — class one being of the best quality, class five being the worst. No water was found fit to be classified as class one, just under 19.9 percent of water was sorted into classes two and three, 32.9 percent was found to be in class four and a whopping 47.2 percent was placed in class five.

Since air pollution has been the most popular of the country’s problems in recent years, the underground water pollution has been all but forgotten, Zheng Yuhong explained in a China Water Resources report.

Treating the underground wells of their ammonia, nitrite and nitrate contamination is no easy task, Ma Jun warned. Overexploitation could lead to cave-ins and rock fractures.

The shallow, contaminated waters force cities to delve deeper into the surface in search of clean water, but that only puts more stress on the deep reservoirs.