The inhalation of dust can often trigger a bodily response, commonly in the form of a sneeze. This is a key way that the lungs protect themselves from airborne particles. Most dust particles are large enough to trigger the body’s natural defense mechanisms, but some are small enough to become lodged in the lungs. Dust particles that become stuck in the lungs can lead to a range of respiratory diseases such as “black lung” and asbestosis.
Outdoors, government agencies monitor the air quality and check for small particulates, whereas indoors, it is the responsibility of the building manager and employer. Organizations should be aware of what matter they’re exposing their employees, customers and even neighbors too, for health reasons and process control. This White Paper from OMEGA Engineering investigates the issues that arise from microscopic particulate matter and how organizations can monitor it. Individual sections address:
- Particulate matter air pollution
- Health risks associated with particulate pollution
- Sources of particulate matter pollution
- How to monitor and control particulate pollution
- Five environments that should be monitoring particulate pollution
- Handheld monitoring equipment
Particulate Matter Air Pollution
Air contains a large amount of particulate matter (PM). Particulates in the air can be caused by many means, including dander release from animals, a dirt road throwing up dust and burning refuse which creates thick smoke. There are two forms of this PM: solid particles and aerosols. Solid particles have a large enough mass that they settle out over time, but aerosols are small liquid or solid particles that remain suspended in air.
PM is classified by its aerodynamic diameter, which is not always the same as its 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 this way simplifies the measurement).
Air pollution standards have traditionally been based around measurements of PM greater than 10 microns aerodynamic diameter (referred to as PM10), where monitoring sites would report the particles captured over a given period and measured in terms of micrograms per cubic meter (μg/m3). Recently, concerns have grown regarding the impact of very fine particles on human health. In response, agencies now prefer measurements down to 2.5 microns aerodynamic diameter and a newer particulate pollution meter will report down to PM2.5.
Health Risks Associated with Particulate Pollution
The lungs facilitate the movement of oxygen from the air to the bloodstream. This occurs in the alveoli, which look similar in nature to bunches of grapes (but far smaller) and are located at the ends of the bronchial branches. Capillary veins in the alveoli walls allow oxygen to diffuse into the bloodstream and receive carbon dioxide from the recirculating blood.
Inhaling draws air into the lungs, and along with it airborne particulates. Larger particles are filtered out in the nose by the mucus, with progressively smaller particles being trapped the deeper into the aerobic tract you go. Mechanisms such as mucus, cilia (tiny hairs) and special cells called macrophages all work together to capture (and remove) particulates.
When PM becomes stuck in the lungs, it can produce effects ranging from the relatively minor, e.g. coughing, to major issues, such as asthma attacks, reduced lung function, and even potentially fatal problems like pneumoconiosis. Health problems most commonly occur with very small PM. When PM is of the order of 2.5 microns, it can easily become lodged in the alveoli and the body reacts in a way that can cause permanent damage.
Sources of Particulate Matter Pollution
Dust occurs pretty much anywhere. An incomplete list includes construction and landfill sites, mines, quarries and manufacturing processes such as milling flour, sandblasting, and textile production. Processes such as paint spraying and machining with cutting fluids can create liquid aerosols commonly referred to as mists. Burning processes, such as open fires and diesel exhausts produce smoke – a solid aerosol. Incinerators can also be an issue in terms of air pollution as the greater combustion efficiency produces smaller particles, normally around the PM2.5 classification.
Particulate Pollution Monitoring
The air quality levels outdoors are monitored via a network of permanent stations. Businesses commonly use similar equipment to monitor the levels of PM emitted through stacks.
Building owners, managers and employers are all responsible for managing the air quality indoors. While permanent monitoring is feasible, sampling studies can be more cost-effective. These can be performed on a fixed schedule – either as part of a process of risk assessment or on an ad hoc basis when there are particular operating processes. The results of such surveys help to identify what type of PPE should be issued to employees.
Processes such as paint spraying, and other coating applications need to be carried out in very clean conditions. Periodic checks using a hand-held monitor is a way of verifying that the filters are performing optimally (perhaps coupled with a handheld anemometer to check airflow).
Five Environments that Should be Monitoring Particulate Pollution
This list excludes medical, pharmaceutical and semiconductors because of their need for extremely high levels of cleanliness, surpassing the capabilities of a handheld particulate pollution meter.
- Burning processes. Incinerators, diesel engines, (such as those used in large generator sets) foundries and welding can all expose workers, and possibly others outside the immediate work environments, to very small particles.
- Manufacturing operations, especially where cutting and spraying take place. Cutting fluids readily form aerosols when agitated by rotating tools or wheels. Grinding, deburring, sandblasting and sawing processes also generate dust with airborne PM of a range of sizes. Textile cutting can generate a large amount of very small fibrous PM. Paint spraying is an obvious source but any liquid mixing, especially if performed without a lid or cover, can create liquid aerosols.
- Mines and quarries are places where cutting and grinding are performed on a large scale. Levels of airborne PM can be high, and depending on the nature of the materials, could carry other health hazards.
- Construction zones and landfill operations both generate dust. While these are outdoors, the problems can be too localized for permanent stations to detect. Frequent checks with a handheld pollution monitor will identify rising PM levels before they become a risk for the workers and those who are downwind.
- Agriculture. Animal dander, dust from plowing or tilling soil and driving over dirt roads, are all problems. Monitoring helps to identify potential issues before they turn into health hazards.
Handheld Monitoring Equipment
HHTP21 handheld particulate pollution meters provide a cheap way of sampling on a routine or ad hoc basis. Using a photodiode sensor, it can measure down to the PM2.5 level with a resolution of 0.1 μg/m3. Temperature and humidity can also be measured, allowing for the capture of environmental conditions at the time of reading. For easy use, the air quality is indicated through a six color LED display and a “Health Index” with alarm.
Handheld Particulate Pollution Meter
The microscopic particles in dust and smoke pose a health risk. Anyone running a business or organization where employees could be exposed to PM should seriously consider setting up a monitoring program. A handheld particulate pollution meter is an inexpensive way of protecting the health of your employees, customers and neighbors.
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.