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Particulate Matter: 

Little things can cause big problems


What is particulate matter?

Where does it come from?

PM 10 & PM 2.5 ... Huh?

Why should you be concerned?



What is being done?

What can you do about it? 



What is particulate matter?

Thick, black smoke belching out of the exhaust pipes of vehicles. Swirls of dust picked up by the wind. Ash and soot coming from your campfire. These are all examples of particulate matter (PM).  PM is the term used for solid or liquid particles emitted to the air. Some particles are large enough to be seen, and others are so small they can only be detected with an electron microscope.



Where does particulate matter come from?

Particulate matter can come from many sources. Generally, any activity which involves burning of materials or any dust generating activities are sources of PM. Some sources are natural, such as volcanoes and water mist. Humans create huge quantities of particulate and many of these sources are regulated, such as smoke stacks at factories, power plants, and auto paint shops. However, there are many sources that are not regulated and your home is one of them. We often burn wood or coal for heat in the winter, we can release dust into the air in our yards, and during renovation, large amounts of dust may be released if they are not kept in check. Vehicles, like our cars and SUVs, produce particulates, as do gas powered lawn mowers, leaf blowers, and weed whackers.



PM 10 & PM 2.5 ... Huh?

The Environmental Protection Agency (EPA), many health professionals, and, of course, the Hamilton County Department of Environmental Services are all very concerned about particulate pollution. In fact, the concern about particulates is related to their very small size.

Since the late 1970's, we only monitored particulate matter pollution that was 10 microns in diameter or less, called PM 10. A micron (or micrometer) is a millionth of a meter. To give you an idea of how small PM 10 is, the dot above the letter "i" in a typical newspaper measures about 400 microns! 

2000 particles of PM2.5 could fit end-to-end across one end of a paper clip!


PM 10 particles are small enough to be inhaled and accumulate in the respiratory system. In the last decade, health studies indicated that particles even smaller than PM 10 can cause even more health problems! Now, in addition to monitoring PM 10, scientists and technicians monitor fine particles called PM 2.5, these particles measure 2.5 microns in diameter or smaller, or about 1/10,000 of an inch. These tiny particles are about 30 times smaller than the width of a hair on your head! These tiny particles are small enough to get inhaled past our defensive nose hairs and into our lungs. But it doesn't stop there! PM 2.5 can pass from our lungs into our blood supply and be carried throughout our bodies.

To protect us from the harm of air pollutants, the U.S. Environmental Protection Agency (USEPA) established National Ambient Air Quality Standards (NAAQS) for criteria air pollutants that are thought to cause the most harm to the health of humans and the environment. Particulate matter is one of these criteria pollutants.

There are two PM 10 standards, a 24-hour standard and an annual standard. These standards are:

  • 150 micrograms per cubic meter (ug/m3) for the 24 hour standard

  • 50 micrograms per cubic meter (ug/m3) for the annual standard

To determine if an area meets the annual standard, data is collected daily and averaged over the entire year. The last three years of  annual averages are used to determine attainment. An area will meet the 24-hour standard if the number of days per calendar year above 150 ug/m3 is equal to or less than "1."

In 1997, the USEPA revised their PM standard to take into account new findings about significant health problems associated with fine particulates, PM 2.5 and smaller. To the old PM10 standards, the USEPA added two new PM 2.5 standards set at:

  • 65 micrograms per cubic meter (ug/m3)as the 24 hour standard

  • 15 micrograms per cubic meter (ug/m3)as the annual standard

Based on the 1999, 2000, and 2001 data, southwestern Ohio will not meet the new fine particulate standard.


Why should you be concerned about particulate matter?


As you have just found out in the section above, some tiny pieces of particulate matter, PM 2.5, are small enough to pass from our lungs to our bloodstream.

PM can alter the body's defense systems against foreign materials, damage lung tissues, aggravate existing respiratory and cardiovascular disease, and can lead to cancer. In some cases, PM exposure can even lead to premature death. Adverse health effects have been associated with exposures to PM over both short periods (such as a day) and longer periods (a year or more).

The people who are most at risk are people with asthma, influenza, lung, heart, or cardiovascular disease, the elderly, and children.

The human immune system developed in a time and environment where dust was made of large particles. Humans have developed a means of protecting themselves against these large particles. Particles larger than 10 microns generally get caught in the nose and throat, never making it as far as the lungs. Unfortunately, more recent human activity has created many particles that are much smaller, which can make it past our natural defenses, and can enter our systems. This is why particles smaller than 10 microns are often called "inhaleable particulates" and are regulated by the USEPA. Particles that are smaller than 5 microns can get into the bronchial tubes and the top of the lungs. Particles smaller than 2.5 microns in diameter can get into the deepest portion of the lungs where the gas exchange occurs between the air and blood stream. These are the dangerous particles because the body has no efficient mechanisms for removing them.

New studies have shown that there is an 18% increase in deaths from heart disease among people with long term exposure to particulate matter. "It's very different from what we thought previously," said professor and epidemiologist Arden Pope of Brigham Young University, who led the study. While exposure clearly impacts the lungs, "long-term, chronic exposure to air pollution seems to manifest more in cardiovascular disease than it does in respiratory disease."

This study shows the biological mechanism by which long-term exposure to tiny-particle pollution can actually lead to ischemic heart disease, which causes heart attacks, as well as irregular heart rhythms, heart failure and cardiac arrest. The key is inflammation, Pope said. While strong bouts of pollution can make breathing hard and increase respiratory problems, they also provoke low-grade pulmonary inflammation, accelerating the development of atherosclerosis - a leading cause of heart disease - and altering heart function.

The Air Quality Index (AQI) for particulate matter provides information on the health effects of different levels of particulate in the air.

Air Quality Index (AQI): Particulate Matter (PM)

of Health
Cautionary Statements*
PM2.5 PM10
0 - 50 Good None None
51 - 100** Moderate None None
101 - 150 Unhealthy for Sensitive Groups People with respiratory or heart disease, the elderly, and children should limit prolonged exertion. People with respiratory disease, such as asthma, should limit outdoor exertion.
151 - 200 Unhealthy People with respiratory or heart disease, the elderly, and children should avoid prolonged exertion; everyone else should limit prolonged exertion. People with respiratory disease, such as asthma, should avoid outdoor exertion; everyone else, especially the elderly and children, should limit prolonged outdoor exertion.
201 - 300 Very Unhealthy People with respiratory or heart disease, the elderly, and children should avoid any outdoor activity; everyone else should avoid prolonged exertion. People with respiratory disease, such as asthma, should avoid any outdoor activity; everyone else, especially the elderly and children, should limit outdoor exertion.
301 - 500 Hazardous Everyone should avoid any outdoor exertion; people with respiratory or heart disease, the elderly, and children should remain indoors. Everyone should avoid any outdoor exertion; people with respiratory disease, such as asthma, should remain indoors.


* PM has two sets of cautionary statements, which correspond to the two sizes of PM that are measured:

  Particles up to 2.5 micrometers in diameter (PM2.5)
Particles up to 10 micrometers in diameter (PM10)
** An AQI of 100 for PM2.5 corresponds to a PM2.5 level of 40 micrograms per cubic meter (averaged over 24 hours).
An AQI of 100 for PM10 corresponds to a PM10 level of 150 micrograms per cubic meter (averaged over 24 hours).  



PM impacts the environment by decreasing visibility. You can see this by viewing the Haze Camera that is situated on the roof of the AQMD building in Clifton in Cincinnati. This page has more in-depth information about the effects of particulates on visibility and the types of particulates that cause visibility problems. Compare the haze here in Cincinnati to the haze in your neighborhood. Or perhaps you would like to compare your haze to that in Chicago, Indianapolis, or one of the other cities linked to the Haze Camera network.

PM also affects the environment by harming plant life. This has an effect on the wildlife of the area, as many animals are dependant on the plants for food. This effect can be passed on up the food chain.

Wildlife can also be effected in the same way that humans can, by breathing in the particulates.



What is being done to reduce particulates?

In 1997, the EPA proposed to create a new limit for fine particulate matter (PM 2.5 and smaller). The new limits would allow less than a third of the soot that was permitted by the old PM10 standard to enter the air. For the first time, even the tiniest particles would be controlled. Regions that failed to meet the limits would lose federal highway funds and other federal money.

The rules are part of a move to toughen the Clean Air Act of 1970. That Act sets limits on six kinds of air pollution (known as criteria pollutants): carbon monoxide, lead, nitrogen dioxide, sulfur dioxide, ozone, and particulates. Every few years, the EPA reviews these limits, as they did in 1997.

Data from 1999, 2000, and 2001 indicate that southwestern Ohio will not meet the new fine particulate standard.

Industries must have emission equipment in place to reduce particulate pollution. In southwest Ohio, this is monitored by Environmental Compliance Specialists here at the Hamilton County Department of Environmental Services, Air Quality Management Division. All facilities that plan to install or operate a regulated emission unit are required to have a permit. The Environmental Compliance Specialist also conducts inspections to ensure that the facility is operating within their permit.

Construction zones try to wet the area they are working in to avoid dust. At the landfill (where our garbage goes) the dirt roads are kept wet and the vehicles clean their wheels before going back onto the street again, all to avoid dust problems. There are many different things that are done that we may not be aware of that try and limit particulate pollution.



What can you do about particulate matter? 

There are many simple things that you can do to reduce particulate pollution. Try to cut down on opportunities for combustion to occur by conserving energy in your home and workplace. Remember, the regulations about open burning, make sure that your vehicle is properly maintained, think about alternative ways to travel such as walking, biking, taking the bus, or ridesharing. If there is a dust, smoke, or other particulate problem within the air near your home, school, or office, please remember to call the Air Quality Complaint Hotline at 513-946-7777 (for Butler, Clermont, Hamilton, and Warren Counties).