Through research, technology may be available in the future to achieve even better controls. MACT is Maximum Achievable Control Technology and refers to the maximum degree of pollution reduction obtainable. We are only beginning to find out what happens to emissions. Little is known about the interaction of chemicals in ambient air, but some effects such as smog , ozone depletion, acid rain , and climate change are a few of the known consequences when air emissions interact, are blown by the wind, and are deposited in cities, fields, and wetlands . These effects have generated new research to find answers.
Sunlight can destroy or alter some airborne chemicals.
Rain, snow, and wind affect where and when air pollutants are deposited on land or water. The standard is even stricter for dioxins and PCBs. Basically, at-source control is a pollution prevention approach that seeks to keep hazardous wastes from being produced. BACT, on the other hand, is the best technology for treating, containing, or reducing discharges and emissions.