Measuring Particle Pollution

Inhaling dust frequently triggers a sneezing attack. It is one way the lungs protect themselves against airborne particles. Most are of a size that activates the body’s natural defense mechanisms but a proportion is small enough to lodge deep in the lungs. Once there they can cause severe respiratory diseases like asbestosis and “black lung”.

Government agencies observe outdoor air quality for small particulates, but indoors it is the responsibility of building managers and employers. Organizations should know what they are exposing their customers, employees and even neighbors to, for health reasons, and sometimes also for process control. This article from OMEGA Engineering explores the problems brought about by microscopic particulate matter and how an organization could monitor it.

Particulate Matter Air Pollution

Air is filled with particulate matter (PM). Animals release dander, driving down a dirt road throws up dust and burning refuse produces smoke. This PM takes two forms: solid particles and aerosols. Solid particles have sufficient mass to settle out over time, but aerosols are liquid or solid particles so small they remain suspended in air.

PM is classified by its aerodynamic diameter, which is not essentially the same as actual size. The aerodynamic diameter of a particle is, “… the diameter of a unit density sphere that would have the identical settling velocity as the particle.” (Sizing particulates in this manner simplifies measurement).

Air pollution standards have traditionally been based on measurements of PM more than 10 microns aerodynamic diameter (referred to as PM10). Monitoring sites would report the particles captured over a period of time in terms of micrograms per cubic meter (µg/m3). Very recently, concerns have grown over the impact of extremely fine particles on human health. In response, agencies currently favor measurement down to 2.5 microns aerodynamic diameter. Consequently, a newer particulate pollution meter will report in terms of PM2.5.

Air pollution

Air pollution

Health Risks Associated With Particulate Pollution

The lungs exchange oxygen with the blood. This takes place in the alveoli which appear similar to bunches of grapes (but far smaller) at the ends of the bronchial branches. Capillary veins in the alveoli walls allow oxygen to move into the blood and then return carbon dioxide.

Inhaling draws air into the lungs and along with it airborne particulates. Larger particles are filtered out in the nose with increasingly smaller particles being trapped deeper down. Mechanisms such as cilia (tiny hairs), mucus and special cells called macrophages all work to capture particulates.

When PM gets into the lungs it has effects ranging from the moderately minor, like coughing, to asthma attacks, reduced lung function to potentially serious problems like pneumoconiosis. Health problems occur mostly with the extremely small PM. When it is of the order of 2.5 microns it can lodge in the alveoli where the body reacts in a way that leads to permanent damage.

Sources of Particulate Matter Pollution

Dust occurs almost anywhere. An incomplete list comprises of construction and landfill sites, quarries, mines, manufacturing processes like sandblasting, milling flour and textile production. Processes like paint spraying and machining with cutting fluids generate aerosols of liquids normally termed mists. Burning processes like diesel exhausts and open fires generate a solid aerosol called smoke. Incinerators can be a specific problem in terms of air pollution as higher combustion effectiveness produces smaller particles, frequently down around the PM2.5 classification.

Spray painting

Spray painting

Particulate Pollution Monitoring

Overall levels of outdoor air quality are monitored through a network of permanent stations. Businesses frequently use similar equipment in order to monitor the levels of PM being emitted through stacks.

Indoor air quality is the responsibility of building owners, employers and managers. While permanent monitoring is feasible, sampling studies may be more cost-effective. These could be carried out on a fixed schedule, perhaps as part of a process of risk assessment, or on an ad hoc basis when specific processes are operating. The results of such a survey would help decide what type of PPE should be issued to employees.

Some processes, such as paint spraying or other coating applications, need to be carried out in extremely clean conditions. Periodic checks with a hand-held monitor could be a way of determining that filters are functioning effectively (possibly coupled with a handheld anemometer to check airflow).

Five Environments that Should be Monitoring Particulate Pollution

This list excludes pharmaceutical, medical and semiconductors because of their requirement for very high levels of cleanliness, exceeding the capabilities of a handheld particulate pollution meter.

  1. Burning processes: Incinerators, diesel engines, (such as those employed in large generator sets) foundries and welding are all capable of exposing workers, and possibly others outside the immediate work environs, to extremely small particles.
  2. Manufacturing operations: Particularly where cutting and spraying take place. Cutting fluids readily form aerosols when agitated by wheels or rotating tools. Grinding, deburring, sawing and sandblasting processes also produce dust with airborne PM of a wide range of sizes: Textile cutting can generate a lot of extremely small fibrous PM. Paint spraying is an obvious source but any liquid mixing, particularly if carried out without a lid or cover, can generate liquid aerosols.
  3. Quarries and mines: These are places where cutting and grinding are carried out on a large scale. Levels of airborne PM can be high, and based on the nature of the materials, could carry various other health hazards.
  4. Construction zones and landfill operations: These both produce dust. While these are outdoors, the problems can be too local or transient for enduring stations to detect. Recurrent checks with a handheld pollution monitor will recognize increasing PM levels before they become dangerous for workers and those downwind.
  5. Agriculture: Animal dander, plus driving over dirt roads and dust from plowing or tilling soil, can all be a problem. Monitoring helps recognize possible problems before they become health hazards.

Handheld Monitoring Equipment

HHTP21 handheld particulate pollution meters provide an economical way of performing sampling on a routine or ad hoc basis. Using a photodiode sensor, this measures down to the PM2.5 level with a resolution of 0.1 µg/m3. Humidity and temperature are also measured, permitting capture of environmental conditions at the time of reading. For ease of use, air quality is specified by both a six color LED display and through a “Health Index” with alarm.

Handheld particulate pollution meter

Handheld particulate pollution meter

Protecting Health

The microscopic particles in smoke and dust can be extremely dangerous to health. Anyone operating an organization or business where people could be exposed to particulate matter should think about setting in place a monitoring program. A handheld particulate pollution meter is an inexpensive means of protecting the health of customers, neighbors and employees.

This information has been sourced, reviewed and adapted from materials provided by OMEGA Engineering Ltd.

For more information on this source, please visit OMEGA Engineering Ltd.

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