It would be nice if there were only one hazard rating system (HRS). But that’s not so. It would be nice if classification of hazards by these rating systems created obvious pathways to safer operation. But that’s not generally so either.
Those doing cleaning with chemicals need to know about hazards presented by use of those chemicals. Users, safety managers, and environmental regulators all value quantitative information about hazards. The reason hazard rating systems exist is because the statement “…This isn’t bad stuff…” doesn’t adequately support judgments about worker safety.
HRSs number more than 50! Technologists created them because they believed the needs of those in which they have an interest weren’t being met by the existing systems. They include regions and countries, trade associations, suppliers, safety and environmental associations, laboratories, individual firms, and this author. Your HRS should effectively describe all hazards, allow comparison among chemicals, propose protection schemes, and be incredibly easy to understand and communicate.
There are five general types of HRS: 1 to 4 NFPA, safety and risk phrase, numerical, exposure limit probability, and the SAPMA system.
The US-based National Fire Protection Association (NFPA) created the HRS most commonly known in the US. The US Department of Transportation (DOT) requires its use in the “four diamond” labels found on all chemical packages. Each diamond pertains to one of three categories of risk: health, flammability, and reactivity. The fourth diamond warns of specific hazards. Each category is divided into four levels of hazard potential with increasing numbers indicating increasing hazard. Numerical values for flammability are based on flash point. Those for health are: deadly (4), extreme danger (3), hazardous (2), slightly hazardous (1), and normal (0).
The NFPA system is easily communicated but doesn’t speak to protective schemes. A trade association has developed the HMIS training system using the NFPA HRS.
Safety and Risk Phrase
The EC through its European INventory of Existing Chemical Substances (EINECS) and the UK through its Chemical Hazard Information and Packaging for Supply (CHIPS) have separately created complex HRSs which they require to be used in package labeling and worker training. That the HRSs are similar but different reflects the difficulty of achieving international agreements.
Here, specificity is valued over simplicity and ease of communication. Hazards are classified by numbered phrases which describe a specific risk or protective method. There are more than 70 of each in both the EC and UK systems. Most MSDS sheets now contain codes such as R23 or R45 which correspond to certain “risk phrases,” and S17 or S24, which correspond to certain “safety phrases.” Don’t confuse R22 (“don’t swallow”) with R2 (“explosive”)!
In the CHIPS system, chemicals are classified differently depending upon whether they are being transported, or supplied (sold). The reasons for this are the different types of risk exhibited in different situations.
In the 1990s, the US EPA was seeking methods to measure progress in pollution prevention. The Indiana Relative Chemical Hazard Score (IRCHS) was the work product whose development they contracted.
It is probably the best available algorithm for comparing hazards in use of various cleaning solvents. A database has been developed of rankings (scores) for more than 1,250 solvents (chemicals). They are sorted by CAS number and value.
The algorithm is complicated. There many components, but there are two general elements: a normalized worker exposure hazard value; and a normalized environmental hazard value. The workplace hazard value has three components: the health effects; the routes of exposure; and a safety hazard value. The environmental hazard value has four components: water; air; land; and a global hazard value. Each of these seven components has sub-components.
Like all HRSs, the ratings are no better than the data input from which they are calculated. Not all of the input are absolute measurements. Some are judgments.
The IRCHS is easy to communicate (lower scores are safer) but it can’t be understood by most (because the algorithm is complicated) and doesn’t speak to protection from hazards.