Frequently reported causes of occupational asthma, by molecular weight
| Agents and source | Workers at risk | |
| High molecular weight agents | Animal urine and proteins (eg, mice, rats, cows, horses, insects). | Laboratory work, veterinarians, farmers, animal handlers, greenhouse workers. |
| Cereal grains and flour (eg, wheat, rye, barley). | Bakers, pizza and pastry makers, grain storage handlers, millers. | |
| Enzymes (eg, amylase, protease, lipase). | Bakers, pastry makers, food process workers (amylase), cleaners, healthcare workers, detergent manufacturers. | |
| Natural rubber latex. | Healthcare workers, rubber glove makers. | |
| Other animal or plant-derived products: milk and egg protein, beans (eg, green coffee, castor, soy), spices, gums (eg, acacia, guar). | Food producers and processors, bakers, cooks. Pharmaceutical industry, printing, carpet making (gums). | |
| Seafood proteins (eg, fish, crustaceans, molluscs). | Fish and seafood processing. | |
| Low molecular weight agents | Acid anhydrides (eg, tri-mellitic anhydride, phthalic anhydride). | Makers and processors of epoxy resins (adhesives, surface coatings). |
| Acrylic monomers (eg, cyanoacrylate, methyl methacrylate). | Adhesive work, dental professionals, aestheticians, printing. | |
| Biocides (eg, aldehydes, chlorine releasing agents, quaternary ammonium compound). | Healthcare workers, cleaners, swimming pool attendants. | |
| Colophony (rosin) in solder flux (abietic acid). | Electronic soldering, work with adhesives and surface coatings. | |
| Di-isocyanates (eg, toluene di-isocyanate, methylene diphenyl di-isocyanate, hexa-methylene di-isocyanate). | Spray painters, foundry workers, makers and processors of polyurethane substances (eg, adhesives, foams, hard surface coatings). | |
| Drugs (eg, opiates, penicillins, other antibiotics). | Pharmaceutical manufacture, healthcare workers with repeated exposures. | |
| Metals (eg, chromium, cobalt, nickel, zinc) and metalworking fluids. | Welders, metal platers, hard metal manufacturing. CNC grinders and lathe operators. | |
| Persulphates and henna. | Hairdressers. | |
| Platinum and other precious metal salts. | Refinery workers. | |
| Some wood dust (eg, iroko, obeche, sapele, western red cedar) and MDF (medium-density fibreboard) | Carpenters, joiners, millers, forestry workers. |
CNC, computerised numerical control; MDF, medium density fibreboard.