​NIOSH staff recently identified diallyl disulfide, a chemical in garlic vapor, as the potential cause for eye and respiratory irritation reported by employees who processed garlic at a food processing facility. The organic sulfur compound is also a decomposition product of allicin, an organosulfur compound that is released when garlic is chopped or crushed. Personnel from the NIOSH Health Hazard Evaluation (HHE) Program conducted screening sampling and collected personal air samples during two site visits to the facility in response to a request from managers at the company. Management was concerned about employees’ reports of eye irritation, burning eyes, blurred vision, and burning and sore throats during garlic processing. NIOSH’s approach was to determine which volatile organic compounds (VOCs) were being released during this process and suggest actions the employer could take to minimize irritation and, if possible, eliminate the need for respiratory protection during garlic processing and cooking.

Although the company required employees who chopped garlic to wear a respirator, the written respiratory protection program indicated that the respirator cartridges should be changed when employees could smell garlic while wearing the respirator. OSHA’s respiratory protection standard states that cartridge change-out schedules should be based on measured concentrations.

According to NIOSH, no occupational exposures limits exist for diallyl disulfide. For a similar compound, allyl propyl disulfide, a product of onion processing, the OSHA permissible exposure limit (PEL) and NIOSH recommended exposure limit (REL) are 2 ppm as a time-weighted average (TWA). NIOSH also has a short-term exposure limit (STEL) for allyl propyl disulfide of 3 ppm. The ACGIH TLV for allyl propyl disulfide is 0.5 ppm TWA.

NIOSH’s personal air sampling at the food processing facility found large variances in concentrations of diallyl disulfide for some work tasks. Exposures for garlic cutting ranged from 0.09 ppm to 0.63 ppm. The agency noted that other compounds found in area air samples can cause irritation and allergy.

“Although we do not know if [diallyl disulfide] alone is responsible for the eye and respiratory irritation reported by employees who processed the garlic, [the chemical] is a main component of garlic oil and is considered a mucous membrane and skin irritant and skin allergen,” NIOSH’s report concludes.

The HHE report urges the employer to improve local exhaust ventilation (LEV) above the cooking kettles to help control garlic vapors, install LEV in the garlic-cutting areas, and change respirator cartridges at regular intervals. The agency also advises keeping the kettle room under negative pressure during garlic processing to help contain odors. Other NIOSH recommendations, including further suggestions for engineering and administrative controls, are available in the full HHE report ().

Chemical sampling information for diallyl disulfide is available on OSHA’s .