Chemical Pneumonitis

17. (1995):

The exposure to gases and vapours may cause more problems than just an unpleasant smell. Certain gases and vapours (and mists and dusts) may be irritating to the lung, in the short or long term, or lead to sensitisation (occupational asthma). These symptoms are usually predictable, and depend on their solubility in lung fluids, and chemical reactivities. However, some gases and vapours when inhaled may have a delayed response. This response may be called -

• Chemical Pneumonitis,
• Delayed Pulmonary Oedema, or
• (Chemically induced) Adult Respiratory Distress Syndrome (ARDS) resulting from an inhaled toxin.

ARDS may also be caused by: an infection, aspiration of gastric contents, smoke inhalation, oxygen toxicity, near drowning, transfusion reactions, trauma, rapid ascent to high altitudes, renal problems, and post irradiation of the lungs. In general, the term chemical pneumonitis or delayed pulmonary oedema is preferred. Other toxic effects on the lungs, such as pulmonary sensitisers, fibrogenic dusts, agents causing benign pneumoconiosis, methaemoglobin formers, chemical asphyxiants, simple asphyxiants, and cholinesterase inhibitors, are not considered in this hazard alert.

Chemical pneumonitis is generally caused by a gas (or vapours) that are slightly soluble in the fluid lining the respiratory tract. These gases tend to reach the lower regions (gas exchange regions) of the lung. With time, the gases may dissolve into the fluid, or react with it, to produce an irritation. This irritation may result in the accumulation of fluid in the lung (pulmonary oedema).

As airway resistance increases due to mucus accumulation and smooth muscle contractions, chemical pneumonitis may develop further. Hypoxaemia (a decrease in oxygen concentration in the blood) and cyanosis become obvious. This is generally the result of poor gas (oxygen and carbon dioxide) exchange, and a reduced vital capacity of the lung. An increased effort and rate of breathing becomes obvious.

Other symptoms, such as: restlessness, anxiety, cough, expectoration, chest tightness, substernal pain, dyspnea (difficulty in breathing), cyanosis, rales, and rhonchi may be present.

Chemical pneumonitis can be a life threatening condition. As the term 'delayed pulmonary oedema' indicates, that the condition is delayed. The symptoms may not appear until several hours after exposure (sometimes as long as 24 hours after the event). The main problem with chemical pneumonitis is that the delay pulmonary oedema may occur when the victim is away from medical care, with serious consequences in life expectancy. Prompt and appropriate medical treatment can save lives.

In an accident at a Hong Kong University, a PhD student assisted in cleaning up a spill of acryloyl and methacrylic anhydride. About 12 hours later the student developed breathing difficulties, and was placed in intensive care. The student died later that night, about 24 hours after exposure.

Some chemicals which may cause delayed pulmonary oedema are -

• Acid gases - HCl, HBr, HI,
• Gases which hydrolysis to Hydrochloric acid - BCl3, SiH2Cl2, NOCl,
• Acetyl chloride,
• Allyl chloroformate,
• Amines,
• Ammonia,
• Anhydrides - which release acids in water,
• Chlorine and chlorine releasing compounds,
• Dimethyl sulfate,
• Ethyl chloroformate,
• Ethylene oxide,
• Hydrofluoric acid as a mist, gas or vapour,
• Gases which hydrolysis to Hydrofluoric acid - BF3, ClF3, COF,ClO3F, PF5, PF3, SiF4, N2F4, OF2,
• Mercaptans,
• Metal fumes - example: cadmium oxide fume,
• *Oxides of nitrogen - NO, NO2, N2O3,
• *Ozone,
• *Phosgene,
• Propionyl chloride,
• Pyrolysis products of plastics and fluorocarbons,
• Sulfur dioxide,
• Triethylamine,
• Vanadium pentoxide.

* indicate the classic chemical pneumonitis agents.

This is not a complete list. It is only meant to illustrate the range of possibilities.

A list of severe pulmonary irritants is given in Appendix A.

Prevention

The most important means of avoiding chemical pneumonitis is prevention. This involves -

Information:
The material safety data sheet (MSDS) for particular compounds should be consulted in order to determine whether the gas, vapour, or even particulate can cause delayed pulmonary oedema.

The Poisons Information (phone: 13 11 26) is another source of toxicological information.

Safe handling:
Any hazardous material should be handled under the most appropriate condition. This generally involves a fume cupboard. Safe handling information is also available in the material safety data sheet.
In the event of an emergency and/or spill -

• Evacuate the immediate vicinity.
• Inform building management as the air-conditioning may need to be shut down.
• Gather appropriate Personal Protective Equipment. This may involve: Breathing apparatus, respirator, gloves, safety glasses, etc.
• Using appropriate spill containment, spill control procedures, and absorbing material, collect the material for disposal. This information is usually available in the MSDS.
• Dispose of material thoughtfully. This information is available in the MSDS or Hazardous Waste Safety folder.

Safe storage:
The storage requirement of each class of chemical - be it gas, liquid or solid, will vary. The appropriate storage requirements for each chemical should be enforced, giving due consideration to the hazard, quantity of substance, and risk involved.

First Aid Procedures

This condition results from -
inhalation

• Remove to fresh air.
• Avoid physical exercise (even if patient is without symptoms).
• Transport to hospital (by ambulance, if necessary) accompanied by the Material Safety Data Sheet.
• Artificial respiration and oxygen treatment may be necessary.
• Treat other symptoms of the chemical exposure as required.
• Continue medical observation for 24 - 48 hours because of the dangers of delayed pulmonary oedema.
• Complete rest for at least 24 hours is recommended.

Bacterial pneumonia may develop.

Keep this sheet accessible for an emergency.

References:

Clinical Toxicology of Commercial Products, 5 th edition, R. Gosselin, R. Smith, and H. Hodge, Williams and Wilkins, London, .

Hunter's Diseases of Occupations, edited by: P. Raffle, W. Lee, R. McCallum & R. Murray, Hodder and Stoughton, London, 1987.

Manual of Acute Respiratory Care, G. L. Zagelbaum & J. A. P. Pare, Little, Brown and Company, Boston, 1982.

Patty's Industrial Hygiene and Toxicology, Volume 2B: Toxicology, 3rd edition, 1981, John Willey & Sons, USA.

Proctor and Hughes', Chemical Hazards of the Workplace, 3 rd edition, N. Proctor, J. Hughes, G. Hathaway, and M. Fischman, Van Nostrand Reinhold, New York, 1991.

Appendix A

Severe Pulmonary Irritants

Acrolein
Ammonia
Antimony
ANTU
Beryllium and beryllium compounds
Boron trifluoride
Bromine
Butyl mercaptan
Cadmium dust fume
Chlorine
Chlorine dioxide
Chlorine trifluoride
1-Chloro-1-nitropropane
Chloropicrin
Chromic acid and chromates
Chromium, metal and insoluble salts
Cotton dust, raw
Diazomethane
Diborane
1,1-Dichloro-1-nitroethane
Dichloroethyl ether
Diisopropylamine
Dimethylamine
Dimethyl sulfate
Ethanolamine
Ethylene chlorohydrin
Ethyleneimine
Ethylene oxide
Ethyl mercaptan
Fluorine
Hydrogen chloride
Hydrogen fluoride
Hydrogen sulfide
Iodine
Ketene
Maleic anhydride
Methyl bromide
Methylene bisphenyl isocyanate
Methyl iodine
Methyl isocyanate
Methyl mercaptan
Nickel carbonyl
Nitric acid
Nitroethane
Nitrogen dioxide
2-Nitropropane
Oxygen difluoride
Ozone
Paraquat
Perchloromethyl mercaptan
Perchloryl fluoride
Phosgene
Phosphine
Phosphorus trichloride
Phthalia anhydride
Selenium hexafluoride
Silicone tetrafluoride
Sulfur dioxide
Sulfuric acid
Sulfur pentafluoride
Tellurium hexafluoride
Toluene-2,4-diisocyanate
Tributyl phosphate
Uranium (natural), soluble and insoluble compounds
Vandium pentoxide
Zinc chloride fume

Reference: Proctor and Hughes', Chemical Hazards of the Workplace.

For further information contact:
OHS Officer, e-mail: OHS.Officer@anu.edu.au