Particulate pollution

Did You Know?

• Particulate matter of less than 2.5 micrometers was found to cause oxidative stress in the aquatic invertebrate Tigriopus japonicus.
• Rats exposed to ambient particulate matter showed a significant increase in neutrophils and a significant decrease in lymphocytes.

Atmospheric particulate matter

Atmospheric particulate matter, also called particulate matter or PM, consists of solids and liquid particles suspended in a gas, most often Earth's atmosphere. These particles are divided into primary types, such as mineral dust, which are emitted directly, and secondary types, such as ammonium nitrate, which form through gas-to-particle conversion in the atmosphere. Natural sources include volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray, while human activities like burning fossil fuels in vehicles, wood burning, stubble burning, power plants, road dust, wet cooling towers, and various industrial processes also generate substantial amounts.

Coal combustion in developing countries is the primary method for heating homes and supplying energy. Salt spray over the oceans is the overwhelmingly most common form of atmospheric particulate, and anthropogenic aerosols currently account for about 10 percent of the total mass of aerosols in the atmosphere. Microplastics are an emerging source of atmospheric pollution, particularly fine plastic fibers light enough to be carried by wind; they cannot be traced back to their original sources and are found in remote regions.

A common source of airborne microplastic fibers is plastic textiles, and while most come from land, microplastics also enter the atmosphere through ocean and sea mist. Domestic combustion pollution, mainly from burning wood, gas, and charcoal in heating, cooking, agriculture, and wildfires, contains carbon dioxide, carbon monoxide, nitrogen monoxide, polycyclic aromatic hydrocarbons, and fine and ultrafine particles. In the United Kingdom, domestic combustion is the largest single source of PM2.5 annually, and in some towns and cities in New South Wales, wood smoke may be responsible for 60% of fine particle air pollution in winter.

Research from 2015 estimated that 38% of European total particulate pollution emissions come from domestic wood burning.

Marine debris

When waves break and wind stresses the ocean surface, bubble bursting and capillary action create marine aerosols, which are particles suspended in water. These particles, along with marine debris, are a form of water pollution measured as total suspended solids under the U.S. Clean Water Act. Some particles can float in both air and water, and pollutants can travel through the air to land in water or fall as acid rain. The main marine aerosol is pure sea salt, with global emissions ranging from 2,000 to 10,000 teragrams each year. These aerosols scatter light, help form cloud condensation and ice nuclei, and thus influence the atmospheric radiation budget. When mixed with human-made pollution, they also affect biogeochemical cycles by depleting acids like nitric acid and halogens.

Space debris

Space debris consists of particulates in the vacuum of outer space, specifically particles from human activity that remain in geocentric orbit around Earth. The International Association of Astronauts defines space debris as any man-made Earth-orbiting object that is non-functional with no reasonable expectation of resuming its intended function or any other authorized function, including fragments and parts. Space debris is classified by size and operational purpose into four subsets: inactive payloads, operational debris, fragmentation debris, and microparticulate matter.

Inactive payloads are launched objects that have lost the ability to reconnect with their operator, preventing return to Earth. Operational debris includes matter from propulsion, such as upper rocket stages and ejected nose cones. Fragmentation debris results from explosions, collisions, or deterioration. Microparticulate matter includes particles, gases, and spaceglow that typically cannot be seen singly with the naked eye.

Research concluded that impacts from Earth orbital debris could pose greater hazards to spacecraft than the natural meteoroid environment, leading NASA to begin the orbital debris program in 1979 with an initial budget of $70,000. The program initially characterized hazards and created mitigation standards, and by 1990 had created a debris monitoring program that sampled low Earth orbit for debris as small as 6mm using the Haystack X-band ground radar.

Epidemiology

Particulate pollution exists worldwide in many sizes and chemical makeups, and it is a major subject of health research. Scientists typically sort particulate matter into two groups: PM10, or coarse particles, which are 10 micrometers or smaller, and PM2.5, or fine particles, which are 2.5 micrometers or smaller. Because PM2.5 particles are so tiny, they can travel deep into the lungs and, after enough exposure, enter the bloodstream. These particles come from both direct and indirect sources, including farming, cars, building sites, wildfires, industrial chemicals, and power plants.

People can be exposed for a short time or over many years. Short-term exposure often leads to breathing problems, coughing, asthma attacks, and airway irritation. Long-term exposure is linked to more serious issues like irregular heartbeat, lung cancer, kidney disease, chronic bronchitis, and early death, especially in those with existing heart or lung conditions. How severe the effects are depends on particle size and a person’s health; older adults, children, pregnant women, and people with weak immune systems face the highest risk.

The U.S. Environmental Protection Agency and other global health organizations have set limits for safe levels of PM2.5 and PM10, but no amount of exposure is known to be completely safe. In Europe, when PM2.5 levels reach 10 micrograms per cubic meter or higher, the daily death rate from all causes rises by 0.2 to 0.6 percent, and deaths from heart and lung diseases increase by 6 to 13 percent.