pollutant

US, China and the European Union each apply their own pollutant thresholds.

Even worse, burning coal produces air pollutants, including sulfur dioxide and nitrogen oxide, that are real threats to human health.

Although it remains in the atmosphere for about 12 years, the "super pollutant" is roughly 80 times more potent than CO2 over a 20-year period.

The report from environment groups Size of Wales and WWF Cymru says the soy is high in phosphorous, and becomes a pollutant when animal manure spread on land runs off into rivers.

Acrid smog blankets the skyline each winter, when cooler air traps pollutants close to the ground, creating a deadly mix of emissions from crop burning, factories and heavy traffic.