How did concerns about sulfate pollution lead to the development of flue gas treatment?

Concerns regarding the environmental impact of sulfates date back to the 19th century, when researchers began investigating the chemistry of rainwater near industrial cities. These early observations highlighted how industrial emissions, particularly from burning fossil fuels, contributed to the formation of acidic compounds in the atmosphere.123

As industrialization expanded throughout the 20th century, the recognition of acid rain as a significant regional environmental threat—capable of damaging forests, aquatic ecosystems, and infrastructure—drove the need for more sophisticated air pollution control measures. This urgency led to the development of flue gas desulfurization (FGD) systems. These technologies were designed to remove sulfur dioxide from flue gas before it could be released into the atmosphere, typically through chemical absorption processes using alkaline sorbents like limestone or lime. The implementation of these treatments was further accelerated by the adoption of stringent environmental regulations, such as the U.S. Clean Air Act of 1970, which mandated significant reductions in pollutant emissions.4132