Particulate Matter (PM) consists of particles with a diameter of 10 microns (µ) or below (PM10). The most health-damaging particles are those with a diameter of 2.5 microns (µ) or less, named PM2.5. These can penetrate and lodge deep inside the lungs and as a result a great number of adverse health effects can develop (2). Particulate Matter (PM) affects more people than any other pollutant (@).

Principal Sources

PM originates primarily from combustion sources such as motor vehicles, power plants and wood burning and also from certain industrial processes. PM consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the air. The major components of PM are sulfate, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water (3).

Recording Data

Air quality measurements are typically reported in terms of daily or annual mean concentrations of PM2.5 particles per cubic meter of air volume (μg/m3). Data is recorded and analysed to evaluate the potential health risks and generate a reading on the AQI.

Where sufficient recording instruments are available to measure the fine PM2.5 particles their concentration is a major contributing factor to the AQI reading. This is due to the damaging health affects associated with the particles being able to lodge much deeper in the body. Where sufficient instruments are unavailable to measure PM2.5 the coarser PM10 is recorded as an indicator of air quality. However as a PM10 dataset does not give an indication of the concentration of finer are particulates a misinterpretation of air quality can take place.

Health Effects

Particle pollution – especially fine particles (PM2.5) – contains microscopic solids or liquid droplets that are so small that they can get deep into the lungs and cause serious health problems. Numerous scientific studies have linked particle pollution exposure to a variety of problems, these include:

  • Cardiovascular and respiratory diseases (This can contribute to premature death in people with heart or lung disease),
  • Nonfatal heart attacks,
  • Irregular heartbeat
  • Aggravated asthma,
  • Decreased lung function,
  • Increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing

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People with heart or lung diseases, children and the elderly are the most vulnerable when exposed to particle pollution. However, even if you are healthy, you may experience temporary symptoms from exposure to elevated levels of particulate pollution.

It must be stressed that the health effects of these fine grains are not yet completely understood. Their is no set threshold for when symptoms do occur from where effects are apparent.

Health Guidelines for Outdoor PM2.5

An annual average concentration of 10 µg/m3 (microgram particles per cubic meter of air volume) was chosen by World Health Organisation (WHO) as the long-term guideline value for PM2.5 exposure while a daily exposure of 25 µg/m3 was established in the 2005 Global Update Guidelines. Studies have proven that exposure to PM2.5 above these thresholds for period a period of 3-4 years can have damning consequences. The United States Environmental Protection Agency (EPA) guideline values differ slightly citing an annual average concentration of 15µg/m3 and a daily concentration of 35 µg/m3

Infact adverse health effects have been identified at values as low as 3–5μg/m3 (PM2.5) following both short-term and long-term exposures.

The WHO also established guidelines for PM10. However it is stressed that the PM2.5 guidelines are the most important to aim for and achieve as these present the greatest health effects.

PM WHO standards

The Chinese central government adopted the WHO guidelines as a goal for future PM2.5 and PM10 emissions.

Besides the guideline value, three interim targets (IT) are defined for annual PM2.5. These have been shown to be achievable with successive and sustained abatement measures. They act as pragmatic steps to help achieve the recommended guidelines displayed above and reduce health associated problems. The table below shows the values for the three interim targets and effects upon human mortality (@).

pm 2.5 guidelines

Health Guidelines for Indoor PM2.5

Controlling pollution emission rates from household energy use is one of the most effective ways of ensuring cleaner air in the home, as this addresses the problem at source (@). WHO’s new indoor air quality guidelines have been developed to inform policy and decision makers as they design and implement programmes to mitigate the impact of health damaging household pollutants and fuels (@). The ultimate aim is to transition to modern household energy as quickly and equitably as possible.

The WHO 2005 Guidelines suggest that the targets established for for PM2.5 and PM10 in outdoor environments are equally applicable to indoor environments.

Further suggestions for indoor PM2.5 emission rates were established in the 2014 WHO household fuel combustion guidelines. New targets suggested that household fuel combustion should not exceed the following targets to achieve minimal health risks (@). These emission rate targets will result in 90% of homes meeting WHO Air quality guideline values for PM2.5 (annual average).

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For vented devices, an average of 25% of total emissions is assumed to enter the room. Separate guidance is provided for unvented and vented stoves as those technologies with chimneys or other venting mechanisms can improve indoor air quality through moving a fraction of the pollutants outdoors (@).

Besides the guideline values, an interim target is defined for indoor PM2.5 to achieve in 60% of homes. The value acts as a pragmatic step to help achieve the recommended guidelines displayed above.

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Evidence reviewed for these guidelines has shown that in order to meet WHO air quality guideline levels, particularly for PM2.5, the use of clean fuels needs to be prioritized (@).

Further Information

Read more more about the World Health Organization’s latest publication of air quality guidelines (2005).

What is PM2.5? A brief overview by Environmental Performance Index

Particulate Pollution information from United States Environmental Protection Agency (2013)

WHO Indoor Air Quality Guidlines: household fuel combustion

Significant health effects were observed in the American Cancer Society’s (ACS) study (Pope et al. 2002)

An association between air pollution and mortality in Six U.S. Cities (Dockery et al. 1993)


What’s in the Air

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