Particles

This page provides information on particles in the air and their effects on our health, ecosystems and visibility. It includes usual levels in New Zealand, and standards and guidelines values to protect human health.

Description

Particles found in the air we breathe vary greatly in size. The greatest health hazard from particles comes from the smallest ones – less than 10 micrometres (10 µm or 10 microns) across – because we easily inhale these small particles into our lungs.

These are classified as: 

PM10 particles with a diameter of 10 micrometres or less
PM2.5 particles with a diameter of 2.5 micrometres or less
TSP total suspended particulate

The diagram below compares the size of PM10 and PM2.5 particles to a strand of hair and a type of beach sand. They are tiny – too small for the human eye to see. 

 

Figure 5: The relative size of particulate matter

Source: Ministry for the Environment

The amount of exposure to particles is often measured in units of micrograms of substance per cubic metre of air (µg/m3).

Sources

PM10 and PM2.5 

Fuel combustion such as burning coal, oil, wood and light fuel oil in domestic fires, transportation and industrial processes.

TSP

Sources include dusty roads, soil tiling, quarries and fuel combustion.

Natural PM10 and PM2.5 particles include sea salt, dust, pollens and volcanic ash. PM2.5 is also formed through chemical reactions in the atmosphere.

Effects on health

When we breathe in, the hairs in our nose and air passages generally remove particles larger than 10 micrometres in size. Particles smaller than 10 micrometres can penetrate into the lungs and affect our health.

Some of the most common health effects include irritation of eyes, throat and lungs. Breathing in these particles can also make existing respiratory conditions such as asthma or bronchitis worse.

Studies show that breathing in these particles can increase the number of hospital admissions and emergency department visits, school absences, lost work days and restricted activity days.

International and New Zealand studies show a correlation between levels of particles and the number of people who die each year (the mortality rate).

Groups most sensitive to particle pollution

children
adults with obstructive lung disease
asthmatics
the elderly

Standards and guideline values to protect health

PM10

In any 24-hour period the average concentration of PM10 in the air should not be more than 50 µg/m3 as per the National Environmental Standards for Air Quality.

The PM10 annual average concentration should not exceed 20 µg/m3 as per the National Ambient Air Quality Guidelines.

PM2.5

The 24-hour average concentration should not exceed 25 µg/m3 and the average annual concentration should not exceed 10 µg/m3, as per the World Health Organization guidelines.

Effects on ecosystems

Air pollutants can settle out of the air onto land and water bodies. From the land they can wash into and concentrate in waterways or be taken up by plants and animals.

When air pollutants come into contact with plants they can impair plant growth. If animals inhale them they can be affected in the same way as humans.

Effects on visibility

Particles in the air reduce visibility because they can scatter or absorb light. Reduced visibility can occur at night or during the day.

visibility degradation caused by winter smog  with clear spring air

 

 

 

 

 

 

These pictures show a comparison of visibility degradation caused by winter smog (picture on the left) with clear spring air in Christchurch. 

Source: Canterbury Regional Council

Usual levels in New Zealand

In most New Zealand cities and towns, PM10 levels are generally below the 24-hour standard and annual ambient air quality guideline value.

Some cities and towns can have quite bad particle pollution, especially in winter. In 2013, the highest PM10 24 hour average concentration recorded at one location was close to 140µg/m3 in 2013.

For more information about particle levels in New Zealand see Environment Aotearoa 2015.

Areas where particles may cause problems

urban areas

especially during winter smog conditions when particles from home fires get trapped close to the ground by temperature inversions

localised areas 

(eg, where there are dusty activities or industrial discharges).

Reviewed:
14/01/16