Coal is one of the most pollution-intensive energy sources on Earth. Burning it releases carbon dioxide, sulfur dioxide, nitrogen oxides, mercury, arsenic, lead, and fine particulate matter into the air. Mining it contaminates waterways and leaks methane into the atmosphere. Among all fossil fuels, coal is the single largest source of air pollution-related deaths worldwide.
What Coal Releases When It Burns
Coal combustion produces a wide range of pollutants. The most significant by volume is carbon dioxide (CO2), the primary driver of climate change. Fossil fuel combustion for power generation is the largest source of CO2 emissions globally, and coal is the biggest contributor within that category.
Beyond CO2, burning coal releases sulfur dioxide (SO2) and nitrogen oxides (NOx). Sulfur dioxide is a major contributor to acid rain, which damages forests, lakes, and buildings. Nitrogen oxides drive the formation of smog and also contribute to acid rain. These aren’t trace emissions. A single large coal plant can release thousands of tons of SO2 and NOx per year.
Coal combustion also emits hazardous air pollutants: mercury, arsenic, lead, nickel, chromium, hydrogen chloride, hydrogen fluoride, formaldehyde, and dioxins. In the United States, regulations introduced in 2012 have reduced mercury emissions from coal plants by 90%, acid gas emissions by over 96%, and emissions of non-mercury metals like arsenic and lead by more than 81%. Those reductions show how much was being released before controls existed, and many coal plants worldwide still operate without comparable technology.
Fine Particulate Matter and Health
The health toll from coal pollution centers on fine particulate matter, known as PM2.5. These are particles small enough to pass through your lungs and into your bloodstream. Coal plants are a major source, but even transporting coal in uncovered trains measurably increases PM2.5 levels in nearby communities.
The consequences are severe. A study tracking the U.S. Medicare population over 20 years estimated that electricity generation from coal was responsible for 460,000 deaths during that period. Globally, roughly five million excess deaths per year are attributable to air pollution from fossil fuel use, and coal is the largest single contributor to that toll.
The specific health risks tied to PM2.5 exposure are well documented. For every one microgram per cubic meter increase in PM2.5, hospitalization rates rise substantially: 10.1% for pneumonia, 7.6% for heart failure, 7.3% for chronic obstructive pulmonary disease (COPD), 5.2% for stroke, and 3.4% for heart attack. People living near coal plants also experience higher rates of asthma flare-ups, missed workdays, and days of restricted activity, with some outcomes showing a one to six percent increase over baseline levels in affected areas.
Methane From Coal Mining
Pollution from coal starts long before the coal reaches a power plant. Mining operations release methane, a greenhouse gas roughly 80 times more potent than CO2 over a 20-year period. Underground mines are responsible for 91% of global coal mine methane emissions, with surface mines accounting for the remaining 9%.
The amount of methane varies enormously by mine. The international standard estimate is about 18 cubic meters of methane per ton of coal mined, but real-world figures range from as low as 0.74 cubic meters per ton in low-methane mines to over 40 cubic meters per ton in “outburst” mines where methane is released in sudden bursts. This variability matters because it determines how coal’s total climate impact compares to other fuels. At mines with high methane leakage, coal’s lifecycle greenhouse gas emissions can be dramatically worse than even the least efficient natural gas systems.
Water Contamination From Mining
Coal mining pollutes water through a process called acid mine drainage. When water flows through abandoned coal mines or over coal waste piles, it reacts with sulfur-bearing minerals to produce sulfuric acid. This acidic runoff drains into nearby streams and rivers, often carrying dissolved heavy metals with it.
The effects on waterways can be extreme. In Maryland’s Aaron Run, acid mine drainage from abandoned coal operations dropped the stream’s pH to 3.5, far below the state’s minimum standard of 6.5 and roughly 1,000 times more acidic than clean water. At those levels, brook trout could not survive in the stream, even though neighboring tributaries supported healthy native populations. Iron sediments from the drainage also clogged the streambed, destroying habitat for aquatic life well beyond the mine itself. This pattern repeats across coal mining regions worldwide: streams turn orange with iron deposits, fish populations collapse, and drinking water sources become contaminated.
Coal’s Share of Global Emissions
Coal has been the dominant source of industrial CO2 for over two centuries. Data from the Global Carbon Budget, tracking cumulative emissions from 1750 through 2024, shows that coal accounts for the largest share of cumulative CO2 emissions from any single fuel source. While natural gas and oil have grown as emission sources, coal remains central to the climate problem, particularly in countries that still rely heavily on coal-fired electricity.
The scale of coal’s contribution is why it receives so much attention in climate policy. Replacing coal with lower-emission energy sources offers some of the largest per-unit reductions in CO2 available.
Can Technology Make Coal Cleaner?
Carbon capture and storage (CCS) technology can trap CO2 before it leaves a power plant’s smokestack. Current standard systems target a 90% capture rate, but recent engineering assessments have found no technical barrier to achieving over 99% capture. The cost increase from 90% to near-complete capture is relatively modest compared to the cost of installing the system in the first place, and some plant designers are now targeting rates well above 90%.
That said, CCS only addresses CO2. It does not eliminate particulate matter, mercury, or the methane released during mining. Scrubbers and filters can reduce SO2, NOx, and heavy metal emissions significantly, as the U.S. reductions demonstrate, but these systems add cost and complexity. No combination of current technologies eliminates all of coal’s pollution streams, and most coal plants operating globally lack even basic emission controls. The gap between what is technically possible and what is actually deployed remains wide.