Diisocyanates are widely used in the manufacture of flexible and rigid foams, fibers, coatings such as paints and varnishes, and elastomers. It is also utilized in the automobile industry, autobody repair, and building insulation materials. Diisocyanate Exposure

A group of low-molecular-weight aromatic and aliphatic compounds, the most common diisocyanates are toluene diisocyanate (TDI), methylene biphenyl isocyanate (MDI), and hexamethylene diisocyanate (HDI). The world production of diisocyanates is estimated to be 3 billion pounds annually, and 280,000 U.S. workers are potentially exposed according to OSHA safety reports.

The major reason for occupational exposure to diisocyanates is the inhalation of the vapor or aerosol; exposure may also occur through skin contact during the handling of liquid diisocyanates. Occupational exposure normally occurs during the production and use of diisocyanates–particularly during the mixing and foaming processes in the polyurethane foam industry. Exposures to airborne diisocyanates may also occur from the melting or burning of polyurethane foams during firefighting.

Occupational exposure standards for diisocyanates are based on respiratory irritation and sensitization and carcinogenesis. The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for TDI is 0.02 part per million parts of air (0.02 ppm), or 0.14 milligram per cubic meter of air (0.14 mg/m3) as a ceiling limit [29 CFR* 1910.1000]. When updating its air contaminants standard in 1989, OSHA decreased this limit to 0.005 ppm (0.036 mg/m3) as an 8-hour time-weighted average (TWA) and 0.02 ppm (0.14 mg/m3) as a short-term exposure limit. The OSHA PEL for MDI is 0.02 ppm (0.2 mg/m3) as a ceiling limit. Diisocyanate Exposure

TDI and other diisocyanates are powerful irritants to the mucous membranes of the eyes and gastrointestinal and respiratory tracts. Direct skin contact with TDI can also cause marked inflammation. Respiratory irritation may progress to chemical bronchitis with severe bronchospasm. Diisocyanates can also sensitize workers, making them subject to severe asthma attacks if they are exposed again–even at concentrations below regulated levels. Sporadic cases of hypersensitivity pneumonitis (HP) have also been reported in workers exposed to diisocyanates. Individuals with acute HP typically develop symptoms 4 to 6 hours after exposure. Symptoms are often flu-like, with fever, muscle aches, and headaches. Symptoms may also include a dry cough, chest tightness, and difficulty breathing. Individuals with chronic HP often experience progressively more difficulty breathing, fatigue, and weight loss.

Case studies performed over the years reveal the potentially serious nature of respiratory disease after exposure to diisocyanates. Companies and managers should firmly adhere to regulatory and exposure limits to ensure the safety of themselves, their workers, the site, and surrounding communities. Besides following regulations and general safety knowledge, managers should have engineering controls such as closed systems and ventilation to help minimize diisocyanate exposure in the workplace.

Exhaust ventilation systems should be designed to capture and contain vapors and particulates. Ventilation equipment should be checked for adequate performance at least every 3 months. Diisocyanate Exposure

Areas containing diisocyanates should be restricted to essential workers. Worker education is a vital component of a good occupational safety and health program. OSHA requires that workers be informed about materials that may contain or be contaminated with diisocyanates, and the nature of the potential hazard. Employers must transmit this information through container labeling, material safety data sheets (MSDS), and worker training.

Each employer who manufactures, transports, packages, stores, or uses diisocyanates or products containing diisocyanates should determine whether the potential exists for worker exposure. When there is potential for diisocyanate exposure, workers should be provided with and required to use appropriate personal protective clothing and equipment such as fixed, personal and portable gas detection solutions.

ION Science is a leading gas detection and prevention company offering a variety of fixed, portable and personal solutions across a vast amount of applications, including industries utilizing diisocyanates. To find out more about products offered by ION Science for diisocyanate detection, or if you have a question for us, contact ION Science today. Diisocyanate Exposure