Air pollutants

Fine particles (PM₁₀ and PM_2.5)

• What are fine particles?
• What are the sources and contributors to fine particles?
• What are the effects of fine particles?
• Standards/guidelines for fine particles
• General trends for fine particles
• What do the particles look like?

What are fine particles?

Fine particles refer to particles that are suspended in the air. They carry cancer causing material into the lungs, and can cause illness and premature death.

Particles are diverse in their chemical and physical characteristics, and can vary in size.

 

• PM₁₀ refers to particles less than 10 microns (µms) in diameter which can remain in the air for several days and can be spread by winds over wide areas or long distances from the original source.
• PM_2.5 is a smaller fraction of PM₁₀ which have a diameter of less than 2.5 microns (µms) which can remain in the air indefinitely.

What are the sources and contributors to fine particles?

Motor vehicles are the main source of fine particles in the Auckland region. Domestic fires also contribute significantly during winter. Windblown dusts, pollens from plants and sea salts are natural sources of particles in the atmosphere. Bushfires, agricultural and forest hazard reduction burning also release small particles into the air.

What are the effects of fine particles?

Fine particles carry carcinogenic (cancer causing) material into the lungs. The finer PM_2.5 particles have the ability to penetrate deeper into the lungs and therefore can cause respiratory diseases and premature deaths.

People most susceptible to the effects of particles include:

• the elderly
• children
• those with respiratory diseases such as asthma and cardiovascular diseases.
  

Fine particles can also reduce visibility, affects plant growth and cause a wide range of damage to surfaces and materials.

Standards/guidelines for fine particles

The PM₁₀ air quality targets for Auckland are 50µg/m³ for a 24 hour average and 20µg/m³ for an annual average under the National Environmental Standards (NES) and Ambient Air Quality Guidelines(AAQG) .

View PM₁₀ trends around Auckland.

Standards/guidelines for fine particles

The PM₁₀ air quality targets for Auckland are 50µg/m³ for a 24 hour average and 20µg/m³ for an annual average under the (NES) and (AAQG).

What do the particles look like?

PM₁₀ (particles smaller than 10 microns) and PM_2.5 (particles smaller than 2.5 microns) are actually mixtures of particles that are lots of different shapes and sizes. The particles are also made of different materials depending on where they came from. The types of particles that we have found on our filters included:

• Combustion particles
• Salt crystals (sodium chloride)
• Mineral material (e.g. soil, silt, clay dust)
• Other crystals - possibly calcium sulphate (gypsum)
• Seeds, spores and pollen (mainly basidiospores which come from fungi)
  

PM₁₀ and PM_2.5 particles are so small that they are invisible to the human eye. You can see what they look like below.

Combustion Particle Westlake View large image	Fungal Spore Khyber Pass View large image
Mineral Material Kowhai View large image	Mineral Material Westlake View large image
Glass Fragment Khyber Pass View large image	Salt Crystal Khyber Pass View large image

These images were taken by the University of Auckland's School of Engineering with their scanning electron microscope. Some individual particles were checked to see what they were made of (using Energy Dispersive Spectroscopy) to help us find out what the particles are. Filters from all sites were tested which showed a combination of many or all of the types of particles shown here. The most common were combustion particles.