IAQUK Resources - Particulate Matter
Sources of Pollution
There are a wide range of particulate matter sources. Some particulates may enter a building from external sources, such as industrial processes, vehicle emissions, air turbulence, lawn moving, wood/coal stoves, fires, cigarette smoke.
Indoor particles may be generated from a material such as talc, floor and other sources of fine powder products.
2.5 microns lead to high plaque deposits in arteries, causing vascular
inflammation and atherosclerosis — a hardening of the arteries that reduces
elasticity, which can lead to heart attacks and other cardiovascular problems.
Researchers suggest that even short-term exposure at elevated
concentrations could significantly contribute to heart disease. If the particle is small and it gets very far into the lungs, special
cells in the lung trap the particles and then they can't get out and this can
result in lung disease, emphysema, lung cancer.
Health effects can include the following:
- Coughing, wheezing, shortness of breath
- Aggravated asthma
- Lung damage (including decreased lung function and
lifelong respiratory disease)
- Premature death in individuals with existing heart or lung diseases
The finer particles pose the greatest threat to human health because
they can travel deepest into the lungs.
Particles are deposited in the lungs by one of four different ways:
interception, impaction, sedimentation, and diffusion.
A particle is intercepted or deposited when
it travels so close to a surface of the airway passages that an edge of the
particle touches the surface. This method of deposition is most important for fibres such as
asbestos. The fibre length determines where the particle will be
intercepted. For example: fibres
with a diameter of 1 micrometre (µ) and a length of 200 µ would be deposited in
the bronchial tree.
When particles are suspended in air, they have a tendency to travel
along their original path. When there is a
bend in the airway system, for example, many particles do not
turn with the air but rather impact or stick to a
surface in the particles' original path. The likelihood of
impaction depends on the air velocity and the particle mass.
As particles travel through air, gravitational forces and air resistance
eventually overcome their buoyancy (the tendency for the particle to
stay up). The result is that the particles will settle on a surface of the
lung. This type of deposition is most common in the bronchi, and the
bronchioles. Sedimentation is not an important factor when the
aerodynamic diameter of the particle is less than 0.5µ. Aerodynamic diameter is
the diameter of a spherical particle that has the same settling velocity as
another particle regardless of its shape, size or density. Using
aerodynamic diameters allows occupational hygiene specialists to compare
particles of different sizes, shapes and densities in terms of how they will
settle out of the air flow stream.
The random motion of particles is similar to gas molecules in the air
when particles are smaller that 0.5 µm. When particles are in random motion,
they deposit on the lung walls mostly by chance. This movement is also know as
the "Brownian motion". The smaller the particle size, the more
vigorous the movement is. Diffusion is the most important mechanism for deposition in
the small airways and alveoli.
Methylene Chloride breaks down into carbon monoxide (CO) in your body.
CO can cause nervous system effects like those described above. Smoking also
puts CO in your blood, so smokers can have these symptoms at lower Methylene
Chloride levels than non-smokers.
CO also stresses the heart, and people with angina (chest pains) from
coronary artery disease are extremely
sensitive to CO; Methylene Chloride can make angina worse, even with exposures
below the limits. People with heart or lung conditions,
smokers, people who are overweight or pregnant, and
people with other exposure to carbon monoxide should limit
their exposures to Methylene Chloride.
Particulates, alternatively referred to as particulate matter (PM) or fine particles, are tiny subdivisions matters of solid or liquid or a mixture of both, that are small enough to be carried by the air and therefore be breathed in by people, penetrating deep into lungs and causing damage.
Particulates may be seen as the most critical of all pollutants, and some estimates have suggested that indoor and outdoor particulates are responsible for up to 10,000 premature deaths in the UK each year.
The solid particles come in numerous shapes and sizes and may be composed of different chemical components. They are divided into two principal groups:
Course particles are less than 10 microns (µm) and more than 2.5 microns in diameter and can penetrate into the respiratory system and lung and can cause damage. One micron ormicrometer, is one millionth of a meter or approximately 1/25,000 of an inch. These particles are about 25 to 100 times thinner than a human hair.
Fine particles measure 2.5 microns or less in size (approximately 1/30th the diameter of a human hair) and can penetrate deep into the body’s respiratory system.
Large particles (above 10 micron) are generally filtered out through the
airways’ natural mechanisms. Nasal hairs
(vibrissae) at the opening of the nostrils trap large particles of dust that
might otherwise be inhaled. The entire respiratory system, is lined with a
mucous membrane that secretes mucus. The mucus traps smaller particles like pollen or smoke. Hair like
structures called cilia line the mucous membrane and move the particles trapped
in the mucus out of the nose. The mucous
leaves the airway by coughing or swallowing.
The 10 micrometer size does not represent a strict boundary between
respirable and non-respirable particles, but has been agreed upon for monitoring of
airborne particulate matter by most regulatory agencies.
The smallest particles, less than 100 nanometers may be even more damaging to the cardiovascular
system. (A nanometer is one-billionth of a meter, a billion is a thousand times bigger than a
million). There is
evidence that particles smaller than 100 nanometers can pass through cell
membranes and migrate into other organs, including the brain. It has been suggested that particulate
matter can cause similar brain damage as that found in Alzheimer patients.
Particles emitted from modern diesel engines (commonly referred to as Diesel
Particulate Matter, or DPM) are typically in the size range of 100 nanometers (0.1 micrometer).
epidemiological research suggests that there may be no threshold below which
health effects do not occur.
health effects include:
effects by absorption of the dust into the blood (eg lead, cadmium, zinc)
- Allergic or hypersensitivity effects (eg some
woods, flour grains, chemicals)
and fungal infections (from live organisms)
(eg asbestos, quartz)
(eg asbestos, chromates)
of mucous membranes (eg acid and alkalis)
deleterious effects on lung function causing marginally increased death rates
and sickness in sensitive people
factors that influence the health effects are:
composition of the dust and its health effects
concentration of the dust
- The size
of the dust (smaller particles tend to have more severe effects because they
may be inhaled more deeply into the lungs)
- The duration
of exposure (possibly in years)
people, such as the elderly and people with respiratory and cardiovascular
diseases, are more susceptible than others to the effects of PM. Susceptible
groups include children and adults with asthma, bronchitis, and respiratory
infections. Researchers are working to better understand the factors leading to
increased susceptibility to PM health effects.
may be especially vulnerable to exposure to PM and other air contaminants
because they breathe more air per pound of body weight relative to adults.
addition, people of all ages who are active outdoors may be at increased risk
because during physical activity greater amounts of PM may penetrate into deep
parts of the lung that are vulnerable to injury. For example, children and adults who
play in outdoor sports teams and participate in other outdoor physical
activities may be at increased risk.