Occupational health data as a basis for process engineering changes: Development of a safe work environment in the sodium azide industry

The development of an occupational health system for a plant manufacturing sodium azide has had to confront biological and hygienic difficulties related to the nature of sodium azide. Sodium azide in pellet form is used as the nitrogen generant for automobile air bags; however, it is manufactured as a very fine powder making exposure control more difficult. Sodium azide is a rapidly active, vasodilatory hypotensive agent that causes headaches and drops in blood pressure. Occupational health assessment of the plant and its employees demonstrated the need for exposure control, based on inspection, interviews, health data, process and site review. Targeted studies demonstrated the nature and magnitude of health effect problems at this plant and the relationship to azide exposure. Engineering and hygiene changes were developed in response to the evidence of worker exposure demonstrated by the targeted studies. The occupational health surveillance system provided a monitor for temporal changes. Results appear to demonstrate over the period of the development of the program, the following changes: (1) reductions in evidence of subjective symptoms from azide exposure (health incident reports of headaches and other symptoms), (2) reductions in objective signs of effects from azide exposure (drops in cross-shift mean arterial blood pressures), and (3) reductions in measured levels of azide exposure. Future studies need to validate the evidence of exposure changes and to further identify additional sources of exposure. Interventions designed to reduce exposures need to be demonstrated to be effective and need to be monitored to demonstrate continuing effectiveness.