Reference

Pisati G, Baruffini A, Zedda S, Toluene Di-isocyanate Induced Asthma: Outcome According To Persistence Or Cessation Of Exposure, Br J Ind Med, 1993;50:60-64,

BOHRF Original Authors' Main Conclusions

The original authors' main conclusions are taken from Abstract, Results and Discussion. They are decided upon by the authors of the BOHRF occupational asthma guidelines and form part of the guidelines.

Patients with toluene di-isocyanate (TDI)-occupational asthma were re-evaluated five years after diagnosis. At follow up 17/60 (group A) had relocated to jobs with only occasional exposure to TDI (15 of them used protective respiratory devices). The remaining 43/60 (group B) avoided further inhalation of TDI by moving to another sector. Group A showed a significant decrease in FEV1 and PD15 methacholine and significant increases in the severity of symptom score and requirement for medication. Group B showed significantly less severe symptoms and a threefold increase in PD15 methacholine (duration of exposure to TDI and of symptoms before the initial diagnosis delineated the patients who recovered from those who did not improve; intermediate values in these features characterised the subjects who improved but did not recover). It is inferred that complete removal from exposure is the only effective way of preventing deterioration in patients with occupational asthma due to TDI. Early diagnosis and early removal from exposure after the onset of asthma are important factors for a favourable outcome of the disease. This approach, however, does not necessarily lead to recovery. Persistence of asthma was associated with the duration of exposure to TDI and of symptoms at work before diagnosis. The use of protective devices or treatment was also unable to prevent the worsening of asthmatic symptoms and further damage to the airways.

BOHRF Associated Evidence Statements

The BOHRF occupational asthma guidelines state that this reference is associated with the following evidence statements

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2+

The symptoms and functional impairment of occupational asthma caused by various agents may persist for many years after avoidance of further exposure to the causative agent.

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2++

The likelihood of improvement or resolution of symptoms or of preventing deterioration is greater in workers who have no further exposure to the causative agent.

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2+

The likelihood of improvement or resolution of symptoms or of preventing deterioration is greater in workers who have shorter duration of symptoms prior to diagnosis.

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3

Redeployment to a low exposure area may lead to improvement or resolution of symptoms or prevent deterioration in some workers, but is not always effective.

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3

Air fed helmet respirators may improve or prevent symptoms in some but not all workers who continue to be exposed to the causative agent.