Kathmandu, June 3 -- Tashi Gyalzen Sherpa never leaves home without his palm-sized air pollution monitoring device. On his iPhone, he has four apps that give him timely updates on the level of air pollution in Kathmandu and in major cities around the world. Ever since he launched Metro-Mask in 2015, a high-tech anti-pollution mask designed in Nepal and manufactured in China, Sherpa says he has become fixated with air pollution.

"In my family circle, I am known as the guy who can't stop talking about anti-pollution masks and air pollution," says Sherpa.

But for a graduate of Fashion Merchandising Management from the Fashion Institute of Technology in New York, pollution wasn't always on his radar. After living in the US for nine years, h...