In today's litigious environment, the selection of cleaning chemicals and instruction for their use are not as simple as repeating what has been done before. Management of workplace and environmental safety requires quantitative evaluation of alternatives, development of safe procedures and process equipment, stewardship of products, and training of workers.

Hazard Rating Systems (HRSs) have been developed to meet these four needs, and others. Their use is mandated by entities whose span of control includes governments and individual laboratories. The common (in the US) National Fire Protection Association (NFPA) scheme, the risk and safety phrase systems used in the EC and UK, and the EPA-sponsored Indiana Relative Chemical Hazard Score (IRCHS) HRSs were covered in the July 2004 column. Other systems are described below.

Exposure Limit Probability

The cornerstone idea is that chemicals which have relatively low exposure limits for entry into the body by inhalation, and are quite non-volatile are safer to use than are chemicals with relatively higher exposure limits which are considerably more volatile. Said another way, it doesnít matter if itís hazardous if it doesnít evaporate.

This idea is advanced by chemical manufacturers whose products have low exposure limits for reasons other than that they present deadly hazard in use. For example, the exposure limit of benzene is 1 ppm; for dibasic acid ester solvents (DBE, etc.), it is 1.5 ppm. These exposure limits, taken alone, would suggest DBE is as lethal as benzene. But, the two hazards are not comparableóbenzene is a carcinogen, while DBE reversibly irritates oneís nose!

The Vapor Hazard Ratio (VHR) HRS is the dimensionless ratio of equilibrium vapor phase concentration divided by the use temperature divided by the exposure limit. The VHR for DBE is 87. That for IPA is 103. And that for benzene is more than 1,000. A variation of this system is to multiply the VHR by either the NFPA flammability rating or the sum of all three NFPA ratings. VHR doesnít speak to protective action.

South African Paint Manufacturers

Their simple and intelligently thought out system reports only in terms of health hazards and what protective equipment should be used to protect against them.

Health hazards are ranked in a numerical system. Protective equipment to combat them is listed simply and clearly. The two are combined into the South African Paint Manufacturers Association (SAPMA) hazard ranking system.

There are four levels of health hazard: minimal (4); slight (3); moderate (2); and serious (1). Please note this order is inverse to the NFPA systemóthere is negligible standardization among HRSs. Nine types of protective schemes are covered, ranging from nothing specific (A) to gloves and safety goggles (C) to ìconsult your supervisorî (K). The rating is a combination of number and letter. The rating 2E (or 2 HE) means moderate risk requiring gloves, safety goggles, and a gas respirator.

SAPMA does not publish a list of chemicals with their ratings; users are expected to classify them. I see this as a strong positive in that those who need to know are part of the hazard classification process. The SAPMA HRS is seriously flawed in that it is limited to health hazards only (flammability or reactivity for example). But, unlike EINECS and CHIPS, it is incredibly easy to communicate.

A Preferred System

This is preferred by absolutely no one except your author, because it has never before been published. Often the best advice is to steal shamelessly from the best. My preferred system has that heritage.

I suggest morphing the simplicity and breadth of the NFPA HRS (which doesnít speak to protective procedures or equipment) into the SAPMA HRS (which does speak to protective issues but is limited in focus to health issues).

The four diamond image would be modified (Figure 1) with a centered symbol in which the code for protective equipment would be inserted. The values showing 1, 2, 3, and F are fictitious. But the preferred change is real: users would now receive simple guidance on the package label about the hazards of the chemical AND about protective equipment required for use with this chemical.

Summary

Hazard rating systems are tools to achieve ends; better choices with less risk and fewer incidents. Though the use of some is required by governments, the use of any HRS can be only a part of a hazard evaluation, process development, and training approach.