What is air pollution?
According to the World Health Organization, air pollution is “any contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere”.  Some of the most common components of air pollution are: particulate matter, ground level ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide.

Understanding the numbers
There are different ways to measure and report air pollution. In Delhi, measurements from the U.S. Embassy air quality monitor come in the form of an AQI- a single number to express overall air quality. Measurements from other sources in Delhi are usually shown as a list of numbers showing the measurements of individual components of air pollution (these can be converted into AQI).  Some monitoring stations report measures in real time, others in daily or annual mean concentration of pollutants.

International standards and benchmarks
The World Health Organization has set safe thresholds of particular pollutants. In the case of particulate matter, no safe threshold has been established (there is evidence that it is harmful at any level) so the benchmark is as low as possible: 10 μg/m3 annual mean.  For perspective, WHO data showed Delhi has an annual average concentration of this pollutant of 153 μg/m3 annual mean.

How bad is the air in Delhi?
Evidence from multiple sources show Delhi has some of the worst air in the world.  According to the World Health Organization, Delhi is currently ranked number one for highest annual concentration of small airborne particles among 1,600 cities.

Air pollution trends and patterns in Delhi
Over the last few years, air pollution in much of India and specifically air pollution in Delhi has been getting worse.  In Delhi, particulate matter pollution, the component of pollution more harmful to health, is usually worst in the winter. Ground level ozone, however, peaked in June.  Day by day, pollution levels often peak around midnight. The Diwali holiday brings lots of air pollution from the celebratory fireworks.

What causes pollution in Delhi?
Current evidence points to the sheer number of air-polluting vehicles on the road. Currently there are 7.4 million vehicles on Delhi roads, and 1,200 more are added each day.

What is being done about air pollution in Delhi?
Efforts to mitigate air pollution in Delhi began long ago, to varying short-term success. A new wave of policies is currently being suggested.

The health effects of air pollution
Air pollution is bad for your health. Adverse health effects can be caused by short and long term exposures to air pollution. Particulate matter is the component of air pollution known to cause the most health impacts as particulate matter of 10 microns or smaller can lodge deep inside the lungs and even enter your blood stream. Children, the elderly and poor people are more susceptible to the harmful health effects of bad air.

Children and air pollution
Children are more vulnerable to the harmful effects of air pollution than adults because their lungs are not fully developed until their late teens. Children’s exposure to air pollution is greater than adults as they breathe more air per pound of body weight. Exposure to air pollution has been shown to cause impacts on the pulmonary development in children.

Activity guidelines
Your chances of being affected by air pollution increase the more strenuous your activity and the longer you are active outdoors in bad air. The U.S. EPA created recommended color-coded charts that have activity guidelines for different levels of pollution.  These charts can be used with the air pollution numbers reported from the U.S. embassy in Delhi (the AQI). If you are looking at air pollution measurements from other sites, pay particular attention to the numbers for particulate matter (PM : PM 2.5 and PM 10) as these are the most concerning to health. You can convert these PM numbers into an AQI number so that you can use the EPA color-coded charts.

Pollution masks
The right mask can provide protection from the harmful health effects of breathing in bad air. But you have to wear it, it has to fit right  (meaning that there be no gaps to allow outside air in), and it has to have the right type of filter and fabric to be effective.

Home air filters
High quality air filters can filter the air of harmful air pollution in closed rooms. Many factors play into the success of these products, including the technology of the product, the size of the room it needs to filter, the pollution load in the air and the cleanliness of the internal filter pieces.

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