IVETTE FELICIANO:

For more than a decade, the number of Guayama cancer cases hovered at about 100 per year. But within a year of the plant's 2002 opening, the number of cases rose by nearly 50%. The most recent figures show that new cancer cases have stayed near that level, spiking even higher in 2013.

From the start, the company was producing Agremax from coal ash.

Coal ash has trace amounts of heavy metals including arsenic, chromium, and mercury–substances that can become hazardous if there is enough present.

According to AES, the plant produces 220-thousand tons of coal ash a year.

But in the company's original contract with Puerto Rico's electric authority, the ash could not be stored on the island, unless it had a beneficial commercial use–which it did.

The plant mixed coal ash with water to create Agremax, that concrete-like material that sits outside the plant. AES marketed Agremax for use in Puerto Rican roads and construction, among other things.

According to the EPA, over two million tons of the material was used in thirty-three sites on the island between 2004 and 2012.

Dr. Gerson Jimenez Castañón is the medical director for Menonita medical center, the only hospital in Puerto Rico's southeast region. He says he began to see a higher influx of patients two to three years after the coal-burning plant was built.