What was the air quality like in nineteenth-century London?

Words can barely describe how bad air pollution was during the late nineteenth century in London, England. Coal was burned in excess, and the soot and sulfur dioxide that resulted is blamed for a shockingly increased mortality rate among infants. Indeed, it is estimated that about 50 percent of the children born in London at the time failed to live past the age of two. So much sunlight was blocked by coal dust that people suffered from lack of vitamin D, with the result being a rise in rickets. And, of course, respiratory ailments were rampant.

What are TSPs?

Total suspended particulates (TSPs) are particles in the air ranging in size from 10 microns on down to less than a micron in diameter (a micron is one millionth of a meter). People can breathe in many TSPs, though larger particles can be weeded out by such things as nose hairs and mucous membranes. TSPs either result from primary sources (e.g., car exhaust, smokestacks) or are formed from secondary sources, such as ammonia and sulfur dioxide combining to form new pollutants (in this case, ammonium sulfate).

What are VOCs?

VOC stands for "volatile organic compound." They are organic chemicals that easily vaporize in the atmosphere.

What is carbon monoxide?

Carbon monoxide (CO) is an odorless, colorless, and tasteless gas that is lethal. Auto exhaust is one common source, but CO can result from the combustion of almost any material containing carbon. The molecules bond to hemoglobin in the blood, preventing the hemoglobin from transporting oxygen through the body as it normally does. Depriving organs and other tissues of oxygen can result in death within minutes. The early symptoms of carbon monoxide poisoning, however, include drowsiness, disorientation, and headaches.

In well-ventilated areas, carbon monoxide poisoning should not be a problem, but in closed-in areas, such as a garage, it is hazardous. This is why you should never leave your car running inside a garage. But carbon monoxide can also come from clogged chimneys, unvented space heaters, gas appliances, grills, and lawn mowers. Homes should be equipped with carbon monoxide monitors as a precaution.

While carbon monoxide poisoning is more likely inside a home or garage than outdoors, this pollutant can be a problem in large urban areas. In 1995, for example, there was a strong temperature inversion in the city of Chicago that caused carbon monoxide levels to be pushed toward the ground, rather than dissipating. The toxic gas then found its way into some homes.

What is sulfur dioxide?

Burning coal is a primary source of sulfur dioxide (SO2) in the atmosphere, and so it was one of the first causes of air pollution, arising during the Industrial Age. Sulfur in bituminous and other forms of coal , when burned, bonds with oxygen to form this pollutant, which irritates eyes and the respiratory system. It is also a source of acid rain. Technologies have been developed that scrub sulfur dioxide emissions from smoke stacks, and have done much to improve air quality. While the United States has dramatically lowered these emissions, other developing nations, such as China and India, do not impose vigorous restrictions on sulfur dioxide from factories and power plants.

What are some other significant air pollutants?

Oxides of nitrogen, including nitrogen monoxide (NO), nitrogen dioxide (NO2) and nitrous oxide (N2O) are also generated by factory and car emissions. These gases are not directly harmful to people, but they contribute to ozone depletion.

What is the Air Quality Index?

The U.S. Environmental Protection Agency (EPA) developed the Air Quality Index as a measure to better advise citizens of pollutants in the atmosphere. To calculate the index, the EPA takes into account levels of carbon monoxide, ozone, nitrogen dioxide, and sulfur dioxide. Each pollutant is measured in parts per billion and compared to an acceptable standard over a certain period of time (24 hours for most pollutants, but ozone is calculated over an eight-hour period). This number is then multiplied by 100 to give the Air Quality Index. In other words, the formula would be (pollutant concentration)/(pollutant goal concentration) x 100 = Air Quality Index. The table below explains the different categories in the index.

Air Quality Index

Air Quality Index

Air Quality

Color Indicator

Health Advisory




No health advisory needed




People who are very highly sensitive to pollution should restrict heavy or prolonged activity


Unhealthy for Sensitive Groups


Older adults, children, and people with heart disease, asthma, or other respiratory ailments should reduce or restrict heavy physical activity




All people should restrict strenuous physical activity, and those who are in unhealthy and sensitive groups should avoid such activity entirely


Very Unhealthy


Everyone should avoid all physical activity




Can potentially have respiratory effects on all people, regardless of health; severe respiratory problems for those with asthma; heart and lung disease is aggravated

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