Protecting Flexible Foam Industry Workers
Occupational Health In The Flexible Polyurethane Foam Industry
To manufacture flexible polyurethane foam, (FPF) substances called isocyanates are reacted with polyols and other chemical raw materials. Isocyanates fully react during manufacturing and aren’t present in the finished product. However, in their raw reactive state, isocyanates must be handled carefully to prevent risk of exposure. The flexible polyurethane foam industry has numerous safety practices in place to protect worker health.
Typical examples of safety practices:
- Engineered ventilation systems
- Production and off-loading emergency shut off controls
- Stack engineering and scrubber technologies
- Spill and emergency management procedures
- Personal Protective Equipment (PPE) for use in high-concentration areas
- Personal and area monitoring
- Risk management training
Best Practices: Effective Risk Management
Higher concentrations of isocyanates may be found in some foam plant areas. However, higher concentrations do not necessarily result in exposure if precautions are taken.
Precautions may include restricting entrance, monitoring, supplied breathing air, use of PPE where needed, forced air ventilation, and possibly stack engineering and/or scrubbers to provide a clean air environment for workers and the community.
Engineered Ventilation Systems And Stack Controls
In areas where there could be isocyanates in the air, a continual supply of fresh air is provided, and very strong exhaust systems capture and sweep fumes and vapors from the production line. Tests indicate that for each metric ton of FPF produced, no more than 1.6 ounces of isocyanate are emitted and managed as a stack emissions. The emmitted isocyanates react readily with relative humidity in the stack, resulting in inert emissions.
Spills are unlikely because of materials handling systems, sealed storage vessels and heavy gauge piping, Systems are specially engineered with isocyanate-resistant seals and spill prevention technologies during unloading and transfer of raw materials. Closed loop systems and monitoring devices with automatic shutoff systems are used to transfer isocyanates, preventing accidental operator error. The chances of spills are remote, but should one occur, specially-trained teams are immediately mobilized onsite to handle them.
Personal Protective Equipment (PPE)
For employees working in an area where isocyanates could be present, personal protective equipment such as respirators may be assigned. Employees are carefully trained in the use and limitations of PPE, which are fitted and tested as necessary.
FPF plant employees are trained on how to safely work in an area where hazardous materials may be present, how to prevent and report accidents, and what to do should an accident occur. Important safety information from Safety Data Sheets (SDS) and the Global Harmonization System (GHS) are available for employee reference. Training is often proactive; for example, if a shipment of isocyanates arrives at the manufacturing plant, plant employees will meet the truck driver, instruct the driver on proper safety procedures at the facility, and maintain contact with the driver throughout the loading/unloading process.
As a precaution, employees may be asked to participate in medical surveillance and health surveys. If the employee will be using PPE, requirements may include a more complete physical exam prior to training, and the completion of PPE fit checks. Medical monitoring provides extra health safety.
Monitoring Worker Health
For more than 28 years, the Polyurethane Foam Association has surveyed flexible polyurethane foam manufacturers in North America to monitor rates of self-reported and medically confirmed Occupational Asthma (OA), a respiratory illness that includes sensitization from exposure to isocyanates.
Research shows that the incidents of OA among flexible foam workers are consistently lower than national averages for asthma among the general adult population. The flexible polyurethane foam industry understands that worker protection is critical to success. And having systems that protect workers from excessive exposure can be more effective than simply monitoring ambient exposure levels.
The chart below compares self-reported and medically confirmed incidents of Occupational Asthma among flexible polyurethane foam industry workers. The OA survey included companies representing more than 90% of North American production volume.
The combined results from foam production worker surveys covering 1988 – 2015 indicate that the incidence of self-reported occupational asthma is very low, representing less than 2% of the surveyed worker population from plant production areas.
The incidence of medically confirmed cases of occupational asthma was even lower among the participating manufacturing sites and currently affects less than 1% of production workers.
The very low number of self-reported or medically diagnosed cases of occupational asthma suggests that existing workplace practices continue to provide effective ways to mitigate potential exposure to isocyanates in the workplace.
The combined data, representing a 28-year history of facilities producing more than 90% of the United States output of flexible polyurethane foam, indicate that these plants operate in a manner that does not contribute to the incidence of occupational asthma. Cases of suspected or medically confirmed occupational asthma are rare among these plants.
Dermal Exposure to TDI
It is a widely understood principle of foam chemistry that isocyanates are completely consumed in reaction with polyols to produce FPF. Some academic studies and blogs claim a residual presence of isocyanates in cured foam. However, there is evidence that the detected TDI is, at least in part, an artifact of the solvent extraction methods which partially decompose the foam into constituent chemicals. The International Isocyanate Institute (III) initiated research by an independent laboratory to evaluate five grades of recently-cured FPF collected by PFA for the possible surface presence of TDI and MDI. The findings should be peer-reviewed and published in 2019. At the May 2019 PFA Technical Session, Tim Feeley of Covestro described the development of the migration testing method used in this research, and reported some test results.
Additional research papers and abstracts on occupational exposure and health risks are available on the Technical Papers page.
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