SANTA GERTRUDES, Brazil The sunset over Santa Gertrudes, a small town 175 miles west of the Brazilian metropolis of So Paulo, is renowned for its beauty at dusk, when shimmering red, orange and pink hues streak across the horizon.

But the dazzling display has a filthy source: Santa Gertrudes has the worst air pollution of any Brazilian jurisdiction listed in the World Health Organizations 2016 ambient air pollution database, with some particle pollution comparable to that of Shanghai.

Residents are forced to sweep their homes several times a day to clear the accumulated dust. At night, it often looks like there are no stars in the sky. And many people in the town say theyre sick from breathing the air.

Theres no way to avoid the dust, said Nelson Rodrigues, a 53-year-old machine technician, as he stood in line at the local hospital, where he was hoping to be treated for what he thinks are pollution-related ailments.

In the seven years he has lived in the city, Rodrigues health has deteriorated considerably, he said. My head feels heavy. I feel shortness of breath and a scratchy throat.

This small town of about 25,000 people owes its livelihood to the rich clay deposits in the area and the 29 factories that make Santa Gertrudes the largest producer of ceramic tile in the Americas. Directly or indirectly, clay has sustained the towns economy for generations but it is also the source of its pollution.