Causes of Occupational Asthma

Occupational asthma is caused by the exposure to certain respiratory sensitisers (sometimes called asthmagens) in the working environment. There are thought to be over 200 individual respiratory sensitisers which can lead to occupational asthma depending on a number of factors based upon the type of asthmagen involved, the frequency of exposure and the general health of the person involved.

It is a legal requirement of the employer to minimise the exposure of known harmful substances, but where it is not possible to prevent the substances from becoming airborne, the employer should provide personal protective equipment (PPE) with the aim of mitigating the potential for employees to inhale harmful substances.Typical job working with airborne particles.

There are over 200 different types of substances that are known to have contributed to occupational asthma cases, with some professions being much higher risk than others.

According to the UK Health and Safety Executive the highest number of new occupational asthma cases are caused by exposure to isocyanates and grain/flour with exposure to wood dusts being the next largest cause so workers that are exposed to these types of compounds or substances are in a higher risk bracket for the development of occupational asthma.

The types are substances that are the highest risk for the development of occupational asthma are listed below.

Substances that have been linked with causing occupational asthma

  • Alpha amylases (typically used in baking and flour milling but also brewing, detergents, animal feed and textile making)
  • Azodicarbonamide (used in the plastics and rubber making industry)
  • Bromelains (used in pharmaceutical drugs as an anti-inflammatory and an aid to digestion)
  • Carmine (used to dye cosmetics and food and drink)
  • Castor bean dust (often used to manufacture paint, plastics, printing ink, cosmetics, and hydraulic fluids)
  • Cephalosporins (an antibiotic)
  • Chloramine-T (used as a disinfectant)
  • Chloroplatinates and other halogenoplatinates (used in the refining of platinum along with electrode and catalyst production)
  • Chromium compounds (found in stainless steel welding fumes, cement and electroplating industry)
  • Cobalt metal and compounds (used in metal production and diamond polishing)
  • Cockroach material (the dust from cockroach material such as bodies, skins, faeces, etc.)
  • Coffee bean dust (the dust from the processing of coffee beans)
  • Cow epithelium/urine (the dust from the hair of cows and dander)
  • Crustacean proteins (from the processing of seafood such as crabs, shrimp, lobster and prawn)
  • Diazonium salts (used in the production of dyes and photocopier paper)
  • Egg proteins (used in the baking industry to glaze products)
  • Ethylenediamine (used in epoxy coatings, resins, various pharmaceuticals, circuit boards and printed metal businesses)
  • Fish proteins (by-product of the gutting of fish)
  • Flour dust (a consequence of various food product production)
  • Glutaraldehyde (a disinfectant used to sterilise medical equipment, and also used in the gas and oil industries)
  • Some hardwood dusts (the dust from 40 species of tree are implicated in the development of occupational asthma)
  • Henna (hair and skin dye)
  • Isocyanates (used in the manufacture of foams, plastic, and varnish)
  • Ispaghula (a laxative derived from Plantago ovata)
  • Laboratory animal excreta/secreta (typically from mice and rates but also insects and other mammals)
  • Latex (used in the production of latex gloves for the healthcare industry – the gloves should be powder free)
  • Maleic anhydride (used in polyester resins)
  • Methyltetrahydrophthalic anhydride (used in epoxy resins and plastic creation)
  • Nickel sulphate (used in electroplating and creation of hard metals)
  • Opiates (drugs such as codeine, morphine and heroin)
  • Papain (used in meat tenderising, production of wool and silk and various pharmaceutical products)
  • Penicillins (forms of anti-biotics)
  • Persulphates (used in peroxide hair dyes)
  • Phthalic anhydride (used to make resins, dyes, pesticides and pharmaceutics)
  • Piperazine (used in the veterinary and oil industry)
  • Psyllium (a laxative from the Plantago)
  • Some reactive dyes (such as those found attached to silk, wool, leather, or cotton)
  • Rosin-based solder flux fume (often used by solderers)
  • Some softwood dusts (usually the dust from coniferous trees. Cedar tree dust has been associated with the development of asthma)
  • Soybean dust (used often to mix with flour)
  • Spiramycin (a fine white powder antibiotic)
  • Storage mites (often found in grain or hay in high humidity regions)
  • Subtilisins (used in detergents, animal feed and leather processing)
  • Tetrachlorophthalic anhydride (used in the production of paints, electronic equipment and plastics)
  • Trimellitic anhydride (used to make wall and floor coverings, plasticisers and wire enamels)

For a full analysis of the type of substances that can cause occupational asthma see Section C of the HSE’s Asthmagen Compendium document.