MYSLOWICE, Poland — The children Karolina Zolna knows huff and puff after a few minutes of exercise. Two years ago, her infant daughter spent four months in the hospital with pneumonia. The doctors did not identify a cause, but to Ms. Zolna, the reason for the baby’s illness was obvious.

She blames the pollution that hangs heavy in the air of her gray hometown in Poland’s coal heartland, Silesia. In the still-chilly early days of spring, thick smoke wafted from most of the chimneys in Myslowice, wreathing the town in a haze that is a constant reminder of residents’ reliance on coal for heat.

A few kilometers away, visible from the town’s main street, stands the tall red and white smokestack of Elektrownia Jaworzno III, a coal-fired power plant. Clouds of white steam billow from its concrete cooling towers.

“It’s definitely too close to people’s houses,” Ms. Zolna, 30, a school secretary, said of the plant. “If you read about this, you know that pollution is not good for health. And if you have children, you know that it affects your children. And there are more and more kids” with breathing troubles, she said. “Both my children have had problems with their lungs.”