Snow-making catalyst is safe, experts say

Silver iodide used in process 'will not pollute or endanger human health'

The heaviest snowfall of the winter, which hit northern parts of the country last week, was augmented by artificial snow-making technology, the China Meteorological Administration said.

From Wednesday to 3 pm on Friday, 720 snow-making operations had been carried out in nine provincial-level regions across northern China. Hebei and Shanxi also conducted 17 snow-making operations via aircraft, the administration said on its website.

"The operations increased snow depths by 7 to 11 percent, which is important in relieving drought, improving soil moisture in wheat growing areas and reducing the risk of forest fires," Li Jiming, a meteorologist, told People's Daily.

According to the administration, 1,752 ground-based snow-making operations have been conducted since Dec 1 in Tianjin; the provinces of Hebei, Shanxi, Liaoning, Shandong, Henan, Shaanxi, Gansu and Qinghai; and in the Inner Mongolia, Ningxia Hui and Xinjiang Uygur autonomous regions.

Eighty-six aircraft operations have been carried out in Hebei, Shanxi, Henan, Qinghai and Xinjiang.

Some netizens have expressed concerns about the safety of the snow-making process, and information has circulated widely online claiming that artificial snow contains potentially harmful silver iodide and warning parents to prevent children from eating it.

Children should also wash their hands after playing with snow to avoid any damage that silver iodide may do to their skin, according to the claims.

It has also been suggested that people wear masks for three to four days after the snow melts to avoid inhaling airborne chemicals.

Some netizens also voiced concerns that such operations might harm the environment by tampering with atmospheric moisture.

Li, said such claims were false, and the use of silver iodide in snowmaking is not harmful to people's health or to the environment.

Snow-making machines use silver iodide as a catalyst. It promotes ice-water conversion and increases the concentration of ice crystals when spread in clouds to amplify snowfall, he said.

"The content of dissolved silver ions in snow is far lower than World Health Organization standards and the national standard for drinking water," Li said. "It will not pollute the environment or endanger people's health."

China has been seeding clouds since 1958 and has always attached great importance to impacts on the environment.

Li said experts have been measuring the silver ion content in some reservoirs in Beijing after cloud seeding every year since 2003, and the average concentration was about 0.00064 milligrams per liter, much lower than the national standard for drinking water of 0.05mg per liter.

Last year, environmental specialists and experts from academic institutions and the meteorology industry studied whether catalysts such as silver iodide caused environmental pollution.

They reached the conclusion, based on scientific studies at home and abroad, that the amount of silver iodide used in weather modification and produced per unit of precipitation is negligible and has little impact on the environment in either the short or long term, People's Daily reported.

"Weather modification is a local practice using a trace amount of the catalyst," Li said. "The time and range of impact is very limited."