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London - New air pollution standards on emissions of mercury and other heavy metals from coal-fired power plants will avert up to 11 000 premature deaths every year in the United States.
The US Environmental Protection Agency says the standards will generate benefits worth between $37bn and $90bn a year - with fewer heart attacks, asthma attacks and sick days - at a cost to coal- and oil-fired power producers of less than $10bn according to the "Regulatory impact analysis for the final air toxics standards", December 2011.
While the advantages of cleaning up US power plants are significant, they pale beside the health benefits and reduced pollution that could be achieved from introducing even more basic technology in China.
Smog cuts life expectancy in northern Chinese cities by an average of 5.5 years per person compared with the country's less-polluted southern regions.
The 500 million residents of northern China lost more than 2.5 billion life-years in the 1990s, according to researchers, and the premature death toll continues to kill millions early even today acoording to "Evidence on the impact of sustained exposure to air pollution on life expectancy", May 2013.
Air pollution is far worse in China, so the benefits from reducing smog could therefore run into hundreds of billions of dollars per year.
Mercury and heavy metals
In the United States, the Environmental Protection Agency's new rules target power plant emissions of mercury and other heavy metals such as arsenic, cadmium, chromium and lead.
Mercury is a toxic metal emitted from most fossil-fuelled power plants which is converted by microbes into methyl-mercury and accumulates in fish, where it enters the human food chain.
Exposure to methyl-mercury has been linked to a variety of neurological problems including reductions in intelligence, impaired motor skills and attention/behavioural problems.
"The population at highest risk is the children of women who consumed large amounts of fish and seafood during pregnancy," according to the US National Academy of Science.
"The risk ... is likely to be sufficient to result in an increase in the number of children who have to struggle to keep up in school."
US power plants belched 53 tons of mercury into the atmosphere in 2005, as well as 350 000 tons of hydrogen chloride, a corrosive substance blamed for respiratory problems, according to the federal government.
Emissions in China are far higher. The country's coal-fired power plants are quite literally poisoning much of the population.
Suspended particulates
While mercury and other heavy metals have received most of the attention, the biggest estimated benefits from the new pollution standards come from reduced emissions of tiny particles just a few micrometres in diameter.
Particles measuring just 10 micrometers or 2.5 micrometers across can become suspended in the air from where they penetrate deep into the lungs and enter the bloodstream, causing cancer.
Suspended particulates, which may be visible as smog or haze, kill thousands prematurely in North America and Europe every year.
Cutting emissions of particulates, known as PM10s or PM2.5s, accounts for most of the measured benefits from the new US power plant rules, including most of the avoided premature deaths, hospital admissions and days off work.
While particulate emissions have been gradually reduced in the United States and other developed economies, they have continued to grow in China.
The concentration of particulates suspended in the air in China's northern cities in the 1980s and early 1990s was already five times higher than it had been in the United States prior to the enactment of the Clean Air Act in 1970.
Existing emission filters
The technology to cut particulate emissions has been available for decades and is not complicated or expensive.
Emissions control technologies include electrostatic precipitators, flue-gas desulphurisation units (FGDs), activated carbon injection, dry sorbent injection, and fabric filters, also known as baghouses.
These technologies can be used individually or preferably in combination to eliminate more than 99 percent of the emissions of particulates, mercury and other heavy metals, as well as acid-rain-causing sulphur and nitrogen oxides (SOx and NOx).
All these technologies are already in widespread use in the United States and Europe. In 2012, U.S. power producers captured 52 million tonnes of fly ash, according to the American Coal Ash Association.
"Fly ash is a powdery material that is captured by emissions control equipment before it can 'fly' up the stack," the association says.
Almost 45% of this fly ash was recycled into concrete (12 million tonnes), construction fills (3 million tonnes), blended cement (2 million tonnes), and a host of other applications. The rest is sent to landfill.
In addition, FGD units, known as scrubbers, use lime or limestone to absorb sulphur and other elements from flu gases to produce synthetic gypsum and other saleable compounds.
In 2012, power plants produced almost 24 million tonnes of FGD gypsum, of which 12 million was recycled into commercial products.
Historically, all these coal combustion products would have been sent up the stack and discharged into the atmosphere. In China, many of them are still being emitted this way.
But US and European power plants have been using electrostatic precipitators, scrubbers, fabric filters and other emissions controls for years.
The American Coal Ash Association - which aims to find environmentally acceptable and commercially beneficial ways to manage coal combustion products such as fly ash - was founded as long ago as 1968.
Cutting China's smog
Smog in China's cities is often presented as if it were the same problem as greenhouse emissions and climate change.
In fact the two issues are separable, and cutting smog is the easier of the two to solve.
China could significantly reduce its air pollution by enforcing the same emission control techniques that have been used in the United States and Europe for the last 30 years.
Central and provincial governments have already made a start in compelling power producers to fit FGD units, electrostatic precipitators and fabric filters according to "Emissions of air pollutants from power plants in China", 2012.
There are some questions about whether those tools are always switched on, however, as power producers try to save money according to "China's war on pollution needs more than words", March 12, 2014.
And the coal-fired boilers that supply northern China's district heating systems continue to belch pollution with few controls.
China could cut air pollution by retiring these small, old coal-fired boilers and replacing them with larger, modern power plants fitted with proper control technology.
China's health crisis is an immediate problem that requires an urgent response. The technology already exists for China to clean up its pollution in the short term, even while the country figures out how to cut greenhouse emissions in the longer term.
