Some respiratory agents may cause only respiratory irritation, while others can cause permanent damage or death. Small, respirable particles carried deep into the lungs are a serious health hazard. For example, long-term inhalation of excessive dust causes excessive scarring or hardening of the lungs, typically known as pneumoconiosis. Toxic fumes can occur when cutting or welding zinc or cadmium coatings, lead-painted surfaces and epoxy coatings. Burning materials such as plastic pesticide containers produce thick smoke that may contain chemical residue and, therefore, present a serious respiratory hazard.
Dust can be extremely hazardous when it contains asbestos, lead or high-protein materials.
Such dust is common during grinding, milling, sanding and drilling operations. Other dusts may be a nuisance but are not considered a serious health hazard. Cleaning grain bins, handling animal feed and bedding, working in a dusty field and sweeping barn floors generate nuisance dust. Of particular concern are mold and fungus spores. These are relevant when moldy hay, silage and grain are being handled.