Medical surveillance and long-term prognosis of occupational allergy due to platinum salts

Purpose

Medical surveillance of workers in precious metals refineries and catalyst production plants is well established in many countries as a measure to prevent occupational asthma due to platinum (Pt) salts. It was the aim of this study to evaluate the impact of medical surveillance and to define prognostic factors with an emphasis on exposure determinants.

Methods

As part of an observational longitudinal study, 96 workers from German precious metals refineries and catalyst production plants with Pt salt allergy underwent a second examination several years (median 67 months) after the initial diagnosis was made.

Results

When the second examination was conducted, 92 subjects (96 %) had already been transferred to jobs with very low or no exposure to Pt salts. The number of subjects with sensitization to Pt salt as assessed by skin prick test (SPT_Pt) decreased from 86 to 52 %, and there was a clear improvement for rhinitis, conjunctivitis and contact urticaria between both examinations. Although the number of subjects with asthma symptoms decreased significantly, at the second examination 74 subjects (77 %) continued to suffer from asthma and 51 subjects (53 %) received asthma medication. Airway obstruction or bronchial hyperresponsiveness persisted in 83 subjects (86 %).

Conclusions

Secondary prevention in subjects with occupational exposure to Pt salts, as practiced for over 25 years in Germany could not avoid persistent asthma in the majority of cases, although improvements occurred. This study reveals the limitations of the concept that removal from exposure after the occurrence of respiratory symptoms may prevent chronic asthma. It is recommended that removal from exposure should be done immediately after the occurrence of a positive SPT_Pt, irrespective of symptoms.