Particulate Matter (PM10 and PM2.5): Definition, Composition and Risks for Health

Particulate matter (PM) refers to tiny particles that are suspended in the air. These particles are a mixture of solid particles and liquid droplets that can contain hundreds of different chemicals. Particulate matter is categorised based on the size of the particles. The two main categories are PM10 and PM2.5.

PM10 refers to particulate matter that is 10 micrometres or less in diameter. These are coarse particles that generally come from crushing and grinding operations such as vehicle emissions, dust from roads or industrial sites, pollen, and mould spores.

PM2.5 refers to fine inhalable particles with diameters of 2.5 micrometres or less. These particles can penetrate deep into the lungs and cause significant health effects. PM2.5 generally comes from fuel combustion from motor vehicles, power generation, industrial facilities, residential fireplaces, and wood stoves.

The chemical and physical properties of particulate matter vary greatly depending on the source. Primary PM is directly emitted into the air while secondary PM forms through chemical reactions in the atmosphere. Major components include sulfates, nitrates, ammonium, sodium chloride, carbon, mineral dust, and water. The composition and size determine the potential for causing health problems. Smaller particles can penetrate deeper into the lungs.

Exposure to PM10 and PM2.5 is linked to a number of serious health effects including asthma, lung cancer, cardiovascular effects, birth defects, and premature death. The populations most at risk are children, the elderly, and those with existing heart or lung diseases. Even short-term exposure to elevated particulate matter concentrations can cause adverse health impacts.

The World Health Organization sets air quality guidelines for particulate matter exposure. For PM10, the 24-hour mean guideline is 50 μg/m3. For PM2.5, the 24-hour mean guideline is 25 μg/m3 and the annual mean guideline is 10 μg/m3. Australia's national air quality standards align with WHO's guidelines. Meeting these standards is important for protecting public health from the impacts of particulate matter pollution.

What is Particulate Matter?

Particulate matter (PM) refers to tiny solid particles and liquid droplets found suspended in the air. It is a complex mixture that consists of varying combinations of chemicals, metals, soils or dust particles, and organic materials like smoke, soot, and pollen.

Particulate matter is characterised by the size of the particles. The particles can range from a few nanometers up to tens of micrometres in diameter. The size affects the chemical composition as well as the behaviour of the particles in the atmosphere. The smaller the particle size, the longer they tend to stay suspended in the air. Larger particles like dust tend to settle faster.

What are the different types of Particulate Matter?

Particulate matter is commonly classified based on the particle size. PM10 refers to coarse particles that are 10 micrometres or less in diameter. PM2.5 refers to fine particles that are 2.5 micrometres or less. Ultrafine particles are smaller than 0.1 micrometres.

Particulate matter can also be categorised based on chemical composition. Major components include sulfates, nitrates, ammonium, sodium chloride, carbon, mineral dust, and water. The composition depends on the source.

Finally, particulate matter can be classified according to the source. Primary PM is directly emitted into the atmosphere. Secondary PM forms through chemical reactions. Sources include motor vehicles, power plants, industrial facilities, agricultural activities, wildfires, and more.

What does PM10 mean?

PM10 stands for particulate matter 10 micrometres or less in diameter. It includes inhalable particles with diameters between 2.5 and 10 micrometres.

PM10 consists of coarse particles that generally originate from crushing or grinding operations. Major sources include road dust, industrial emissions, construction sites, mining operations, agricultural activities, and natural sources like pollen.

PM10 can remain suspended in the air for long periods and travel long distances. Exposure can irritate the eyes, nose, and throat. Epidemiologic studies link PM10 exposure to respiratory and cardiovascular health effects.

What does PM2.5 mean?

PM2.5 stands for particulate matter that is 2.5 micrometres or less in diameter. These are fine particles found deep in the lungs when inhaled.

PM2.5 originates from fuel combustion, motor vehicles, power generation, industrial facilities, residential heating, forest fires, and chemical reactions in the atmosphere. The particles have a high surface area which makes them an effective carrier of toxic substances.

PM2.5 can travel deep into the respiratory system and reach the bloodstream, causing inflammation and exacerbating lung and heart disease. Long-term exposure increases mortality risk. PM2.5 also contributes to haze and reduced visibility.

What is the composition of particulate matter?

Particulate matter consists of a complex mixture of chemical components including sulfates, nitrates, ammonium, sodium chloride, carbon, mineral dust and water. Metals like lead, nickel, cadmium, vanadium and manganese are also found. Organic compounds such as polycyclic aromatic hydrocarbons (PAHs) may also be adsorbed onto the particles.

The chemical composition of particulate matter depends on its source and atmospheric conditions. For example, particles from motor vehicle emissions contain more carbon while secondary particles formed from gaseous precursors contain more sulfates and nitrates. Geography also affects composition. Coastal areas have higher sodium chloride levels.

What are the major sources of particulate matter?

Natural Sources

Natural sources include sea salt, volcanic eruptions, forest fires, windblown dust, pollen and fungal spores. These account for around 90% of total global PM emissions.

Anthropogenic Sources

Human-caused sources include fuel combustion from motor vehicles, power plants, industrial facilities and residential heating. Agricultural activities, construction, mining and various industrial processes also generate significant PM emissions.

Geographical Variation in Sources

While natural sources dominate on a global scale, human sources generate higher local impacts in populated areas. Developed countries have stricter air pollution controls so anthropogenic PM is lower. Developing nations have higher PM from industry, domestic heating and older vehicles.

What are the Harmful Effects of particulate matter on Humans?

Exposure to particulate matter is linked to increased respiratory and cardiovascular morbidity and mortality. Short-term effects include eye, nose and throat irritation, coughing, sneezing, runny nose and shortness of breath. Long-term exposure can lead to the development of chronic bronchitis, reduced lung function, lung cancer and increase the risk of cardiovascular diseases.

Children, elderly and those with pre-existing heart or lung diseases are most vulnerable. Pregnant women, diabetics and low-income groups also face higher risks from PM exposure.

What are the international Laws to reduce particulate matter?

The World Health Organization provides Air Quality Guidelines for PM exposure. Countries around the world have established laws and regulations to meet WHO standards. These include setting national air quality standards, emission limits for major sources, monitoring requirements, and control programs.

International efforts like the Paris Agreement, Gothenburg Protocol and Cairo Guidelines address particulate matter reduction through energy policy, transportation and industrial emission controls.

What is Australia doing to prevent air pollution?

Australia has adopted WHO's PM guidelines in the National Environment Protection (Ambient Air Quality) Measure. Other policies like vehicle emission standards, building codes and state clean air regulations aim to control sources. The National Clean Air Agreement provides a framework for cooperative action.

Environmental consultancies support industry compliance through air quality monitoring, emission audits, dispersion modelling, and by identifying cost-effective solutions. Their technical expertise helps in drafting environmental impact statements and navigating air regulation.