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NH Environmental Public Health Tracking Program
Particulate matter

Fine particulates (PM2.5)

Fine particulates are microscopic particles (solid, liquid, or both) in the air that are less than 2.5 micrometers in diameter (see picture for relative size). There are many different particulate species and their toxicity ranges from non-toxic to extremely toxic. Particulates can sometimes be very acidic (e.g., sulfuric acid droplets which derive from sulfur dioxide emissions). Fine particulates can be emitted directly into the air from combustion or lofting (agriculture, roadways, wind), or secondarily from chemicals already in the air (e.g., when water vapor condenses on sulfate ions to create sulfuric acid droplets).

Human hair and fine particulates

Size matters. Small particulates can penetrate deep into the lungs, however large particulates, >10 micrometers in diameter, typically get caught in nasal passages before entering the lungs, although they can cause eye, nose, and throat irritation. Coarse particulates (between 2.5 and 10 micrometers) can enter larger passages in the lungs but are lower in concentration due to EPA's regulatory efforts.

Fine particulate events can occur at almost any time. During the day, emissions sources are strongest, causing higher particulate concentrations. At night, a lowering of the boundary layer can concentrate particulates near the surface. In summer, higher temperatures and relative humidity helps secondary particulate formation. In the winter, temperature inversions (which occur frequently in the winter in NH's valleys) can trap layers of colder air near the surface where residential wood-smoke emissions can concentrate at significant levels.

Being exposed to particle pollution for short durations (hours or days) can:

Being exposed to particle pollution for more than a year is linked to heart and lung problems like:

These effects lead to more hospitalizations, more emergency department visits, and premature death. Sensitive people such as older adults, people with diseases like asthma or congestive heart disease, and children are more likely to be affected by PM2.5 exposures.

In people with heart disease, short-term PM2.5 exposure has been linked to heart attacks (acute myocardial infarctions) and irregular heartbeats. Short-term exposure has also been linked with early deaths, usually in people who already have a serious health problem like lung or heart disease. Healthy children and adults usually do not have serious problems from short-term exposure to particle pollution but may experience minor problems like a scratchy throat or scratchy eyes when particle levels are elevated.

Reduce Your Risk

In order to breathe the healthiest air in NH, you should spend as much time outdoors on good air quality days (as it is probably better overall than indoor air), and to reduce your overall physical activity and time outdoors on poor air quality days.

Guidelines for protecting your health:

Know how to identify poor air quality days. Stay aware of local air quality alerts and forecasts and follow any instructions given.

If you can't find an alert or forecast, be cautious during the following conditions:

On good air quality days, spend as much time outdoors as possible. Outdoor activity is good for your health, and indoor pollution levels for dust, allergens, and toxins are often higher than outdoor levels.

To learn how to reduce your exposure to indoor pollutants:
Go to:

Tracking Particulate Matter (PM2.5)

NH EPHT is tracking particulate matter 2.5 in New Hampshire. Data about particulate matter 2.5 are available on the Environmental Health Data Integration Network (EHDIN).

Environmental Public Health Tracking Program
NH Department of Health and Human Services, Division of Public Health Services
29 Hazen Drive, Concord, NH 03301
Tel: (603) 271-4988 800-852-3345 ext.4988

copyright 2009. State of New Hampshire