After fossil fuel-fired power plants and vehicle emissions, one of the largest sources of air pollution is industrial boilers. On April 29, EPA proposed tighter Clean Air Act regulations for emissions from industrial boilers, process heaters, and some solid waste incinerators.
- Proposed regs  (includes fact sheets and more for each proposed reg). EPA release.  EPA contact: Cathy Milbourn,  202-564-7849.
The proposed air toxics standards address emissions of mercury, cadmium, dioxin, furans, formaldehyde, hydrochloric acid, and other pollutants. The proposals cover emissions from three types of combustion sources:
- AREA SOURCE FACILITIES: Boilers at industrial, commercial, or institutional facilities that can emit up to 10 tons per year (tpy) of any single air toxic, or less than 25 tpy of any combination of air toxics. According to EPA, 183,000 area source boilers currently operate at 92,000 US facilities. In the next three years, 6,800 new ones will be installed.
- MAJOR SOURCE FACILITIES: Boilers that can emit more than 10 tpy of any single air toxic, or more than 25 tpy of any combination of air toxics. EPA estimates that 13,555 major-source boilers and process heaters are operating in the US; and 46 new units would be installed over the next three years. EPA map: Get details on major-source boilers near you. 
- COMMERCIAL AND INDUSTRIAL SOLID WASTE INCINERATION UNITS: These include incinerators that simply burn waste to dispose of it, as well as those from which energy is recovered. EPA map: Get details on incinerators near you. 
The proposed rules are now in a 45-day comment period.
Meanwhile, some industrial boilers might be getting reclassified as incinerators, depending on what kind of fuel they burn. On April 29, EPA also proposed a new Resource Conservation and Recovery Act (RCRA) rule that would "clarify which non-hazardous secondary materials are, or are not, solid wastes when burned in combustion units."
- Proposed rule.  EPA map of potentially affected facilities. 
- Council of Industrial Boiler Owners:  703-250-9042, email. 
Note that these proposed regs do not cover boilers used to heat large apartment buildings and other residential facilities. However, in many US cities, large residential buildings often rely on especially dirty oil-burning boilers for heating.
In December 2009, The Environmental Defense Fund published a detailed report on the high levels of air pollution in New York City caused by apartment building boilers that burn low-grade heating oil.