Whether as dust, fumes, spores or smoke, airborne particles are generated by a variety of processes on worksites. Workers have to be diligent about protecting themselves from the more dangerous particles to which they may be exposed. The immediate consequence of breathing in particles is usually airway irritation, but continued research by industrial hygienists has established connections between chronic conditions or even cancers and minor, acute exposures. A lungful of particles that may not even be noticeable at the time but with the latency of decades, may be eventually realized as a fatality.
Whether the exposure is harmful or not depends largely on the substance in question. The molecular properties of some materials, as well as the means by which the particles are generated, may dictate the size and type of particles that are present. Burning, for example, will produce smoke, which is in fact just heated particles and gases mixed with air. Welding will produce welding fume, which is condensed, oxidizing solid particles from the gaseous phase of different metals. Grinding, cutting, brazing, smoothing and many other processes can also introduce particles into the air that may be harmful.
The respiratory system has a few built-in mechanisms for keeping particles out of the lungs. The cough reflex, for example, forcefully expels air from the lungs to scour offending particles from the airways if they are large enough to be deposited higher up in the nasopharyngeal tract. The mucous in the throat captures some particles, then moves them back out of the airways via a peristaltic elevator. Generally speaking, particles with an aerodynamic diameter greater than 10 µm are captured in the nose and throat and can be expelled easily.
It’s impossible to discuss this topic without mentioning the most notorious example: asbesto
s. The harm from asbestos, particularly in its crocidolite blue form, comes from the structure of the mineral and the tendency for fibrous fracture. Essentially, on a microscopic scale, asbestos fragments into threadlike needles small enough to be inhaled and deposited in the bronchioles and even alveoli (the small sacs in the lungs that perform gas exchange with the circulatory system). Once deposited, these tenacious fibers take up residence in the lungs for good. The immune system responds by building a fibroid tissue around the invader which, usually over decades, can yield certain lung cancers, asbestosis or mesothelioma.
Silica may one day be viewed with the same caution as asbestos, because more and more data is confirming the potential harm from silicosis. Construction sites everywhere are still delinquent in addressing the hazard – you don’t have to look far to find concrete cutting, masonry, or gravel being poured with no breathing protection in sight. Silica is known to cause a similar pulmonary fibrosis as asbestos. The built-in latency of the conditions that result unfortunately makes the causal connection easy to ignore. Yet silicosis cases continue to mount, and eventually practices will have to catch up.
Numerous conditions can stem from particle inhalation above and beyond the specifics discussed above. Pleurisy, pneumoconiosis, allergy sensitization, emphysema and several other chronic conditions can develop just from the mechanical mechanisms of inhaled solid particles. That is to say nothing of the acute and chronic toxicity of some chemical particles, which could fill a hundred more articles.
Suffice it to say, it is worth doing the work to properly assess hazards and put controls in place. The consequences of breathing in particles may be very severe indeed.