November 10, 2014

Parts of the Russian capital, Moscow—including the main shopping areas and parliament buildings just outside the Kremlin—are enveloped in a noxious gas, which is spreading through the city. The gas, hydrogen sulfide, can be highly toxic and smells like rotten eggs. According to experts, exposure to hydrogen sulfide, even in low concentrations, can lead to dizziness, headaches, and nausea. Residents in affected areas are being urged by the Russian Emergencies Ministry to stay indoors.

A cloud of hydrogen sulfide wafts over central Moscow today, the area that  includes the Kremlin (building at right) and other historic buildings in Red Square (Superstock).

The emergencies ministry has confirmed that the source of the gas is a leak from a sulfur-dioxide processing facility at an oil refinery just outside the city. Meteorologists note that the effects of the gas are being made worse by automobile-related smog, which is “not conducive to the rapid dispersion of pollutants in the air.”

January 15, 2012

Air pollution in China’s capital, Beijing, has for the past week greatly surpassed levels considered hazardous by the World Health Organization (WHO). According to the Beijing Municipal Environmental Monitoring Center, the density of a kind of particle pollution known as PM2.5 soared to 700 micrograms per cubic meter in many parts of the city on January 12, a level considered extremely dangerous. An unofficial reading from a monitor at the United States embassy in Beijing registered levels of more than 800 micrograms per cubic meter. According to WHO standards, levels above 25 micrograms are considered unsafe. Yesterday, levels dropped to about 350 micrograms on the Beijing government scale, still dangerously high.

According to the U.S. Environmental Protection Agency, particle pollution, also known as particulate matter (PM), is a mixture of microscopic solids and liquid droplets suspended in air. PM includes such acids as nitrates and sulfates, organic chemicals, metals, soil or dust particles, and such allergens as fragments of pollen or mold spores. PM exists in a wide range of sizes. Particle pollution that is less than 2.5 micrometers in diameter–1/30th the diameter of a human hair–is known as PM2.5. Such pollution can penetrate deep into the lungs. Numerous health studies have linked PM to premature death from heart or lung disease, according to the EPA. The Beijing Shijitan Hospital reported a marked increase in the number of patients seeking treatment for asthma, chronic bronchitis, emphysema, and other respiratory illnesses associated with exposure to PM2.5.

Beijing can easily be seen in a satellite image of northeastern China made on January 3, 2013. (NASA)

Extremely heavy pollution obscures Beijing and surrounding areas in a second satellite image, made on January 14, when pollution levels were 15 times greater than the level considered “safe” by the World Health Organization. (NASA)

Fuel combustion–the burning of fossil fuels and biomass–is a major source of PM2.5. Sulfate particles form when sulfur dioxide emitted from electric power and industrial plants reacts with sunlight and water vapor in the air. Nitrate particles form in the same way from nitrogen oxides emitted by electric power plants and automobiles and other forms of combustion.

Rapid industrialization, a reliance on coal for power, and the explosive growth in car ownership has made air pollution a major problem in China. Weather conditions and the burning of coal for heating generally make conditions worse in winter. When coal, a carbon-based mineral, is burned, sulfur and nitrogen oxides are released into the air. In 2010, China was dependent on coal for nearly 80 percent of its energy and electric power output, according to the International Energy Agency.

Additional World Book articles:

• Smog
• Advances in Understanding Asthma (a special report)
• The Case for Renewables (a special report)
• China’s Global Awakening (a special report)