Reducing industrial emissions of hazardous chemicals is both good for the environment and good for business. Reducing hazardous chemical use can reduce costs of waste handling and regulatory compliance. In addition, employees must be protected from chemical hazards. Federal laws state that workers have both a need and a right to know the hazards of chemicals they may be exposed to in the workplace. Identifying and understanding the hazards of workplace chemicals can help businesses prioritize efforts to minimize or eliminate the use of hazardous chemicals.

Minimum standards for workplace information on chemical hazards are governed by the Occupational Safety & Health Administration’s (OSHA) Hazard Communication Standard (HCS). The HCS establishes requirements for businesses to provide information and training on chemical hazards and the means by which workers can be protected. Requirements include labeling of chemical products and the provision of Material Safety Data Sheets (MSDS) to identify specific hazards of individual chemical ingredients.

Hazardous Chemical Labeling Systems

Product labels typically provide the first line of defense for identifying chemical hazards. The OSHA HCS requires that containers be labeled, marked or tagged with the identity of any hazardous chemical and some general information about the hazards that these chemicals present. These may be communicated through words, pictures, symbols or combinations thereof. There are exceptions to specific container labeling practices. For example, in some cases, individual container warnings may be replaced by local wall signs or placards. The purpose of workplace hazard communication training is to identify the specific practices in use at any particular facility and to ensure that workers clearly understand how hazard information will be communicated in their workplace. A good practical guide to the workplace communication standard can be found at the Interactive Learning Paradigms Incorporated (IPLI) website.

The most common labeling systems are those used to address transportation of dangerous goods and emergency response. In the case of fire or chemical spills, emergency responders need to understand short-term exposure risks to be protected. Furthermore, the appropriate emergency response may vary depending on which chemicals are present in the workplace. These types of labels, for example, the National Fire Protection Association (NFPA) diamond based on NFPA Standard 704, deal with acute hazards and are not intended to reflect occupational risks or chronic exposures from environmental releases.

When considering occupational or chronic environmental exposures, the Hazardous Materials Identification System (HMIS) developed by the National Paint and Coatings Association (now the American Coatings Association) offers a more appropriate set of hazard ratings. The HMIS label includes acute and chronic health effects and personal protective equipment (PPE) recommendations. While not directly focused on environmental releases, the broader set of hazards considered in HMIS offer at least a hint of the potential risk of environmental damage.

OSHA has allowed for great flexibility in labeling as long as a hazard communication program is effective overall. While both the NFPA and HMIS labels are commonly used to satisfy OSHA requirements, there are significant differences between the two systems for human health hazard identification. While flammability, reactivity and other physical hazards are important to worker and public safety, this discussion focuses on the direct toxic effects of workplace chemicals.

NFPA 704 - National Fire Protection Association

The NFPA 704 hazard identification system label is easily recognized by its distinctive diamond shape. The main NFPA diamond is composed of four sub-diamonds. Each sub-diamond includes a number representing the hazard rating from zero (low) through four (high). A blue diamond indicates “Health”, a red diamond represents “Flammability”, a yellow diamond indicates “Instability,” and a fourth white diamond used to address additional hazard criteria, typically the presence of unusual reactivity with water (critical information for first responders).

When addressing chemical toxicity, the most relevant NFPA information is in the blue health hazard diamond. The NFPA describes a health hazard as “the capability of a material to cause personal injury to due to contact with or entry into the body via inhalation, skin contact, eye contact or ingestion.” The numeric levels of human health hazard include:

4 - Materials that, under emergency conditions, can be lethal

3 - Materials that, under emergency conditions, can cause serious or permanent injury

2 - Materials that, under emergency conditions, can cause temporary incapacitation or residual injury

1 - Materials that, under emergency conditions, can cause significant irritation

0 - Materials that, under emergency conditions, would offer no hazard beyond that of ordinary combustible materials

Unfortunately, there is no easy way for employers or employees to relate these numeric hazard ratings to any specific human health hazard. As mentioned previously, NFPA 704 is intended for emergency use and does not address health hazards from chronic or repeated long-term exposure to hazardous materials. At best, users of chemical products can use these hazard ratings to indicate a rough “level-of-concern,” but they should not be used as a substitute for a detailed consideration of any chemical or chemical product’s safety.

Detailed criteria for applying these numeric hazards levels are provided in an appendix to the NFPA 704 standard (Appendix B – Health Hazard Rating). While not freely available, the NFPA 704 standard is available for purchase from the National Fire Protection Association website. Rating values for some common chemicals can be found at a Michigan State University website.

HMIS - Hazardous Materials Identification System

HMIS labels appear as a rectangle-shaped block of colored bars with numeric hazard ratings. HMIS version III, released in 2002, uses labels with a blue "Health" bar on top, a red "Flammability" bar below that, followed by an orange "Physical Hazard" bar and a white PPE area. The level of hazard is identified by a single number in each hazard area ranging from zero (low hazard) to four (high hazard). Prior to 2002, the HMIS label used a yellow “Reactivity” bar in place of the “Physical Hazard” bar. The HMIS labeling program criteria and information for implementation as part of a full hazard communication program are freely available at the J. J. Keller & Associates website.

The HMIS label was developed primarily to address occupational safety. The “Health” numeric hazard rating is similar to the NFPA system:

4 - Severe hazard: life-threatening; major or permanent damage may result from single or repeated exposures; extremely toxic; irreversible injury may result from brief contact

3 - Serious hazard: major injury likely unless prompt action is taken and medical treatment given; high level of toxicity; corrosive

2 - Moderate hazard: temporary or transient injury may occur; prolonged exposure may affect the CNS and lead to apparent intoxication, nausea, headache, dizziness, weakness or fatigue

1 - Slight hazard: minor reversible injury may occur; may irritate the stomach if swallowed; may defat the skin and exacerbate existing dermatitis;

0 - Minimal hazard: no significant health risk; no effect anticipated; practically non-toxic; irritation of skin or eyes not anticipated

Each higher level of hazard indicates a roughly ten-fold increase in toxicity. In addition to the numeric rating, the HMIS III label includes a box to indicate the presence or absence of a hazard from chronic exposure. The box should include a slash if no chronic hazard is anticipated.

As with NFPA 704, the five levels of health hazard provide only a rough guide to chemical hazards. The numeric health hazard rating is based on acute toxicity, with the most toxic effect guiding the applied rating. These effects include skin and eye irritation or corrosion, and toxicity via inhalation, oral or dermal routes (exposure via lungs, mouth and skin). For many occupational environments, chronic exposures to chemicals are common. Effects from long-term exposure might include cancer or harm to specific body organs such as the liver or lungs (target organs). Chronic effects show only as an asterisk (*) in the HMIS system and do not affect the numeric health hazard rating.

A quick guide to the HMIS system can be found at the IPLI website. Detailed guidance can be found in the HMIS Chemical Ratings Guide on the J. J. Keller website. Rating values for many chemicals and supporting data can be found in the HMIS III guidance documents.

Other Labeling Systems

OSHA will soon begin implementing a revision to chemical labeling requirements to conform to provisions of the Globally Harmonized System (GHS) for classification and labeling. Information on the US implementation of GHS should become available in 2012.

Lab Safety Supply company offers labels under their own Hazardous Material Identification Guide (HMIG). The HMIG system closely resembles the HMIS system, however, the Lab Safety Supply website offers few specifics on how the rating numbers are generated. As with the HMIS system, PPE suggestions are incorporated on the label.

The American Chemistry Council has developed a label and safety data sheet (SDS) combined standard maintained by the American National Standards Institute as ANSI Z400.1/Z129.1?2010. This standard is a revision and consolidation of two earlier, related standards and contains details on material identity, manufacturer information, hazard classification, emergency information, instructions on what to do if a hazardous situation has occurred information on the prevention of hazardous situations and guidance on other technical information to be included in an SDS. The standard was designed with the coming US implementation of GHS in mind.

Health Hazard Labels for Some Typical Workplace Chemicals

To illustrate how these systems differ, examine the ratings applied to three common solvents, acetone, methyl ethyl ketone (MEK), and toluene, and a common plasticizer, dibutyl phthalate. Data for the HMIS III label were obtained from the J. J. Keller website. Data for NFPA were obtained from the Michigan State University website.

Chemical	HMIS Health Ratings	NFPA Health Rating
Acetone	HMIS Health: 2 + Chronic *	NFPA Health: 1
Methyl ethyl ketone	HMIS Health: 2 + Chronic *	NFPA Health: 1
Toluene	HMIS Health: 2 + Chronic *	NFPA Health: 2
Dibutyl phthalate	HMIS Health: 1	NFPA Health: 2

MEK, which is highly toxic to the nervous system, among other hazards, is identified in NFPA as a level 1 rating, notable only in its potential for irritation. This would not sufficiently indicate the risk of day-to-day work exposures to MEK. HMIS labels also indicate chronic hazards that are not shown or considered in the NFPA system. Acetone has in general lower toxic properties than MEK, but is rated similarly in both systems.

Toluene is very highly toxic to the nervous system, but rates only a 2 for health in both systems, suggesting only temporary damage. Dibutyl phthalate is widely recognized as toxic to reproduction, but receives a 1 for health in the HMIS III system and includes no indication of the chronic hazard it presents to reproductive health. This suggests that published HMIS III ratings have not been updated with the most current human hazard information.

Summary of Chemical Labels

Employers and employees must be educated on the use of hazardous chemical labeling systems. However, it is important that the limitations of hazardous chemical labeling system used in their facilities also be clearly communicated. As illustrated above, human health ratings can vary depending on the specific labeling system used. Thorough study of chemical hazards should be required using the more complete information provided by Material Safety Data Sheets and other resources.

HMIS III labels provide a more appropriate set of information on occupational and environmental hazards of chemicals. In addition to more complete hazard information, HMIS III labels include chronic health hazard information not available on NFPA 704 labels. NFPA 704 labels are primarily intended to inform on acute hazards to emergency services personnel during accident response.

Labels do provide a first line of defense to inform employers and employees of chemical hazards. Higher hazard values suggest a need for extra caution, but lower values should not be used as an excuse to take risks. When considering workplace and environmental safety, use labels only as a starting point for identifying chemical hazards.