Occupational Dust Exposure Monitoring

Respirable and inhalable occupational dust workplace air monitoring will ensure exposure is below the legal limits and that your control measures are adequate.

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Respirable and Inhalable Dust Exposure Monitoring

Occupational hygienists class dusts as inhalable, thoracic or respirable dust.

Inhalable dust consists of larger particles. These enter the upper parts of the lungs but do not penetrate deeply into the lungs. In contrast, respirable dust consists of smaller particles. Therefore, these enter the deepest parts of the lungs – the gas exchange area. Thoracic dust makes up the remainder of the dust. These particles enter the middle part of the lungs. EH40/2005 – Workplace Exposure Limits only gives limits for the inhalable and respirable fractions so the thoracic fraction is not usually measured. It is important to ensure that dust levels are acceptable by occupational dust exposure monitoring.

EH40 Limits for Occupational Dust

General dust – sometimes called ‘nuisance dust’ is included under COSHH and is classed as a substance hazardous to health once airborne. This applies whenever concentrations of inhalable dust are above 10 mg.m^-3 and respirable dust is at a concentration above 4 mg.m^-3

Monitoring occupational Dust Exposure

Monitoring Dust Exposure

The method of monitoring occupational dust exposure is provided by HSE document MDHS 14/4 ‘General methods for sampling and gravimetric analysis of respirable, thoracic and inhalable aerosols’.

When using this method for a workplace dust survey the consultant uses an IOM sampling head. Generally, they attach a pump for the operative to wear. This is usually on the belt or in a pocket. The occupational hygiene consultant positions the sampling head, which contains a pre-weighed filter, in the breathing zone of the operative (within 300mm of the mouth and nose). The laboratory analyses the filter following MDHS 14/4.

When undertaking dust exposure monitoring, the occupational hygiene consultant will use one of two methods. Firstly, Synergy’s consultants use a cyclone head to collect the respirable fraction only. For the second method, the occupational hygiene consultant uses an IOM head. This is equipped with a foam insert to separate the different size fractions. The consultant uses the IOM head with foam method to simultaneously measure the respirable and inhalable fractions. This method of workplace air monitoring suffers from a higher limit of detection for inhalable dust. For this reason, longer sampling times are necessary.

Health Effects of Dust

Health Effects from Dust

General effects such as coughing, sneezing, throat, eye and lung irritation are likely to occur when significant concentrations of dust are present in the air. Furthermore, prolonged and repeated inhalation of significant concentrations of respirable dust can cause this dust to settle within the lungs and reduce lung function. Other health effects from dust are related to the constituents, such as silica, wood or metals.

Controlling Dust