Making Rain to Clear Smog: An Artificial Solution

Record levels of airborne pollution in Shanghai, China have passed the threshold necessary for normal outdoor activities to resume their course. Its aftereffects have manifested themselves most directly in public sectors such as education and transportation. The closing of schools and the cancellation of flights resulted from the smog infested pollution prompted the Shanghai government to issue the highest level of health warning, according to the World Health Organization (WHO).

After eyeing China’s booming manufacturing industry, it is unsurprising to see why the levels of pollution are so elevated, leading industrial pollution to make cancer China’s leading cause of death, according to the Chinese Ministry of Health. The WHO recommended that the levels of particulate matter (particles found in the atmosphere such as dust, dirt, soot, and smoke) over 300 were hazardous and recommended daily levels of 20 or less.

The particles with diameters less than 2.5 micrometers, designated by the PM2.5 value, are known to produce the greatest health risk since their small size (1/30th the width of the average human hair) can allow them to lodge deeply into the lungs according to the Environmental Protection Agency (EPA).

On Friday, the “Shanghai PM2.5 value exceeded more than eight times the national limit of 75 by reaching 600 micrograms per cubic meter,” causing increased cuts on outdoor activities and prompting children and the elderly to stay indoors, said Shanghai Daily. To combat the incessant smog which has even reached California, the Chinese government has been looking at different venues, such a cloud seeding, to halt the progression of air pollution into an increasing set of domains.

Typical rainfall occurs when super cooled water droplets, which are still in the liquid form but below their freezing point at zero degrees Celsius, form ice crystals. After undergoing this change, the crystals become too heavy to remain hanging in the air and consequently fall and usually melt on their way down to form rain. By seeding the atmosphere with chemicals such as silver iodide, the atmospheric water in even dry areas can be made to coalesce around the induced particles and form ice crystals that eventually form rain in a process known as nucleation.

Such seeds can be launched into the atmosphere through ground generators, planes, or via silver iodide rockets as was done by China in 2008 to prevent rainfall in the opening and closing ceremonies of the Summer Olympics. Reaching the atmosphere, the seeds can facilitate rain formation which can wash down the pollutants from the smog to clear the skies, allowing atmospheric pollution to lessen as a result.

The idea sounds good on paper but contextual pragmatic concerns seem to outweigh the perceived results. Although cloud seeding seems to provide an ephemeral advantage in controlling atmospheric conditions, its long term use in reducing airborne pollution can remain questionable at best if the manufacturing industries and consumers do little to mitigate their dependence on existing methods that contribute to the exacerbating levels of pollution.

“[Cloud seeding] misses the problem,” said Peter Chace, junior chemistry and marine and environmental biology and policy major. “Yes, you will reduce smog in the short term but you’re simply moving that pollution from the air into the soil and watershed where it will accumulate to still affect populations. In addition, the increased rainfall will be over heavily urbanized areas, which already have major issues with runoff that can be extremely damaging to the watersheds. It’s a solution for an after-effect of the bigger problem of overdevelopment.”

Dr. Maryanne Rhett, assistant professor of history, said “It seems to me, if we want to end smog like we see in Beijing, Los Angeles, or Mexico City we need to be more aggressive with our methods of curbing pollutant output. The reality is that it is easy, and surprisingly cheap, to produce environments like this, fixing them seems to be the harder and more expensive proposition. In East Asia and the Middle East, it is not just a matter of asking people to use more public transportation, or limit their use of fossil fuels, the expenses of life have to be factored in to the equation as well.”

“While I am all too aware of the severe air quality challenges that China now faces, I see these challenges as ones where the United States can truly speak from experience in support of China’s efforts to reduce air pollution,” Gina McCarthy, EPA Administrator, said at an event hosted by the Center for American Progress.

Hosting more stringent regulations to curb the overall pollutant output seems to be the main tool left for the long term. McCarthy said,“Before the EPA [in 1970] and our landmark environmental laws in the United States, dark blankets of pollution covered our great American cities – not just Los Angeles but New York and Pittsburgh.”

PHOTO TAKEN from reuters.com