Chemical Hazard Classification

9.  Chemical Hazard Classification

9.1.Chemicals can be divided into several different hazard classes.  The hazard class will determine how a chemical should be stored and handled and what special equipment and procedures are needed to use them safely.

9.2.Each chemical container, whether supplied by a vendor or produced in the laboratory, must include labels that clearly identify the hazards associated with that chemical. In addition to specific chemical labels, hazard information for specific chemicals can be found by referencing the Safety Data Sheet (SDS) for that chemical.

9.2.1. All secondary containers must be labeled with the chemical name (in English), signal word, hazard statement, pictograms and date of transfer or preparation.

9.2.2.  Secondary containers are one to which a chemical or chemical product is transferred or the container in which a new chemical product/reagent is made and stored.

9.2.3.Immediate Use containers are containers which are only expected to last one work shift and are not intended to leave the control of the person who filled them.

9.3 It is essential that all laboratory workers understand the types of hazards, recognize the routes of exposure, and are familiar with the major hazard classes of chemicals. In many cases, the specific hazards associated with new compounds and mixtures will not be known, so it is recommended that all chemical compounds be treated as if they were potentially harmful and to use appropriate eye, inhalation and body protection equipment.

9.4.   Corrosives

9.4.1 A corrosive substance is defined by OSHA as a chemical that can destroy skin tissue.

9.4.2. Acids and bases are the most commonly used corrosive materials in the laboratory.

9.4.3. When working with concentrated corrosive solutions, a full-length lab coat, splash goggles, and chemical resistant gloves must be worn. The use of a face shield over the goggles or glasses protects the entire face in the event of a splash.

9.4.4. These materials must always be used in the chemical fume hood to avoid the inhalation of the vapors.

9.4.5. Acid should always be added to water slowly to avoid splatter.

9.4.6. All labs using corrosive materials must install an eyewash and emergency shower that meets ANSI Z358.1 standard (See Eyewash Station and Emergency Shower Section for requirements).

9.4.7.Hydrofluoric Acid is a particularly hazardous corrosive substance and requires a SOP, with associated training. The antidote, calgonate, should also be placed in the first aid kit in each lab using hyrofluoric acid.

9.4.8. Perchloric acid is a powerful oxidizing agent that may react explosively with organic compounds and other reducing agents. It shall be used only in a perchloric-acid, water-wash-down fume hood of noncombustible construction.

9.4.9. Strong bases are all corrosive and can cause serious chemical burns. Bases generally have good warning properties: they typically have a slippery feeling on the skin. However, if it is not completely removed by rinsing, a solution of a strong base may not cause pain until the corrosive damage is quite severe.

9.4.10. Formaldehyde, formalin, paraformaldehyde, and phenol are corrosives that do not fall into the acid and bases categories discussed above. Formaldehyde is a colorless gas with a pungent odor and is most commonly used as a saturated aqueous solution called formalin. Formaldehyde is a suspected carcinogen.

9.4.11. Phenol is a colorless or pink crystalline solid or viscous liquid with a characteristic sweet, medicinal odor. It is corrosive and considered moderately toxic. Phenol is capable of rapidly penetrating the skin and causing severe burns. It is toxic and even fatal amounts of phenol can be absorbed through relatively small areas of skin.

9.4.12. Care should be taken when storing corrosive materials.   The following protocol should be followed.               

• Nitric acid should be stored separately or in secondary containment from other acids.
• Acids and bases shall be stored separately.
• Perchloric acid shall be stored separately from other acids.
• Glacial acetic acid, even though corrosive shall be stored with the flammable substances.

Table 1: Corrosives

9.5 Flammable and Combustible

           9.5.1.   A flammable liquid is a liquid with a flash point below 100 °F and a vapor pressure not exceeding 40 psi (absolute) at 100 °F. These are categorized as Class I liquids. A liquid with a flash point of 100 °F or greater is classified as a combustible liquid and may be referred to as a Class II or Class III liquid.

Table 2: Flammable Substances

9.5.2. Flammable solids often encountered in the laboratory include alkali metals, magnesium metal, metallic hydrides, some organometallic compounds, elemental phosphorus, sulfur, and powdered metals. Many flammable solids are also considered highly reactive chemicals.

9.5.3. Flammable aerosols as a category are flammable gases compressed, liquefied, or dissolved under pressure, and fitted with a release device allowing the contents to be ejected as particles in suspension in a gas, or as a foam, paste, powder, liquid, or gas. They present multiple hazards including the flammability of the compressed material and hazards associated with compressed gases.

9.5.4. An oxidizing agent is a chemical that has the ability to oxidize other substances, in other words, to cause them to lose electrons. Some oxidizers can spontaneously evolve oxygen at room or slightly elevated temperatures, and can explode violently when shocked or heated. Because they possess varying degrees of chemical instability, oxidizing agents can be explosively unpredictable and, therefore, can be particularly hazardous. Examples of oxidizing agents includes peroxides, hyper peroxides, and peroxyesters.

9.5.5.  Explosive and reactive (unstable) chemicals can be identified a few different ways. The label or SDS may include the pictograms  above, the SDS may include the H codes and statements discussed below, or they may fall into one of the categories discussed further in this section. Some common examples are listed in the table below.

Table 3: Explosive and Reactive Chemicals

9.6 Irritants

9.6.1.. Irritants are defined as non-corrosive chemicals that cause reversible inflammatory effects on living tissue by chemical action at the site of contact.

9.6.2. A wide variety of organic and inorganic compounds, including many chemicals that are in a powder or crystalline form, are irritants. The most common example of an irritant may be ordinary smoke which can irritate the nasal passages and respiratory system.

9.6.3. Consequently, eye and skin contact with all laboratory chemicals should always be avoided.  Symptoms of exposure can include reddening or discomfort of the skin and irritation to respiratory systems.

9.7 Sensitizers

9.7.1. A sensitizer (allergen) is a substance that causes exposed people to develop an allergic reaction in normal tissue after repeated exposure to the substance.

9.7.2. Examples of sensitizers include diazomethane, chromium, nickel, formaldehyde, isocyanates, arylhydrazines, benzylic and allylic halides, and many phenol derivatives. Sensitizer exposure can lead to all of the symptoms associated with allergic reactions, or can increase an individual’s existing allergies.

9.8 Reactivity Hazards

9.8.1. Reactive and explosive substances are materials that decompose under conditions of mechanical shock, elevated temperature, or chemical action, and release large volumes of gases and heat.

9.8.2. Some materials, such as peroxide formers, may not be explosive, but may form explosive substances over time. These substances pose an immediate potential hazard and procedures which use them must be carefully reviewed.  

9.8.3. These materials must also be stored in a separate flame-resistant storage cabinet or, in many cases, in a separate laboratory grade refrigerator or freezer that is designed for flammable/ reactive chemicals.  

9.8.4. Peroxide formers can only be stored in refrigerators when unopened. Once used, they must be stored in a dry environment. Peroxide formers, such as diethyl ether, should also be dated when received and again when opened.

9.8.5. Pyrophoric chemicals are a special classification of reactive materials that spontaneously combust when in contact with air and require laboratory-specific training.

9.8.6.  Flame-resistant laboratory coats or other appropriate flame-resistant protection must always be worn when working with pyrophoric chemicals, along with flame-resistant gloves and training.

9.7.7.  When ordering picric acid, the PI must inform EHS.   This substance should be stored separately and should be disposed of within two years of purchase.

9.9 Hazardous Substances with toxic effects on specific organs

9.9.1.  Substances included in this category include items in Table 4.

Table 4: Specific Organ Toxicity

9.9.2. Symptoms of exposure to these materials vary.  Personnel working with these materials should review the SDS for the specific material being used, take special note of the associated symptoms of exposure, and contact EHS for assistance.

9.10 Particularly Hazardous Chemicals

9.10.1. OSHA recognizes that some classes of chemical substances pose a greater health and safety risk than others. To differentiate this different risk characteristic, OSHA identifies two categories of hazardous chemicals.

• Hazardous chemicals.
• Particularly hazardous substances.

9.10.2. Substances that pose such significant threats to human health are classified as "particularly hazardous substances" (PHSs).  The OSHA Laboratory Standard regulation require that special provisions be established to prevent the harmful exposure of researchers to PHSs, including the establishment of designated areas for their use.

• Use of containment devices such as fume hoods or glove boxes;
• Procedures for safe removal of contaminated waste; and
• Decontamination procedures.

9.10.3. Particularly hazardous substances are divided into three primary types:

9.10.3.1. Acute Toxins

Substances that have a high degree of acute toxicity are interpreted by OSHA as being substances that "may be fatal or cause damage to target organs as the result of a single exposure or exposures of short duration.” These chemicals, associated chemical waste, and storage containers must be handled with care to prevent cross contamination of work areas and unexpected contact.  These chemicals must be labeled as “Toxic.”  Empty containers of these substances must be packaged and disposed of as hazardous waste without rinsing trace amounts into the sanitary sewer system.

9.10.3.2. Reproductive Toxins

Reproductive toxins include any chemical that may affect the reproductive capabilities, including chromosomal damage (mutations) and effects on fetuses (teratogenesis).

Reproductive toxins can affect the reproductive health of both men and women if proper procedures and controls are not used. For women, exposure to reproductive toxins during pregnancy can cause adverse effects on the fetus; these effects include embryo lethality (death of the fertilized egg, embryo or fetus), malformations (teratogenic effects), and postnatal functional defects.  For men, exposure can lead to sterility.

Examples of embryo toxins include thalidomide and certain antibiotics such as tetracycline.  Women of childbearing potential should note that embryo toxins have the greatest impact during the first trimester of pregnancy.  Because a woman often does not know that she is pregnant during this period of high susceptibility, special caution is advised when working with all chemicals, especially those rapidly absorbed through the skin (e.g., formamide).  Pregnant women and women intending to become pregnant should consult with their laboratory supervisor and EHS before working with substances that are suspected to be reproductive toxins.

9.10.3.3. Carcinogens

Carcinogens are chemical or physical agents that cause cancer.  Generally they are chronically toxic substances; that is, they cause damage after repeated or long-duration exposure, and their effects may only become evident after a long latency period.  Chronic toxins are particularly insidious because they may have no immediately apparent harmful effects. These materials are separated into two classes: 

 

Select carcinogens are materials which have met certain criteria established by the National Toxicology Program (NTP) or the International Agency for Research on Cancer (IARC) regarding the risk of cancer via certain exposure routes. It is important to recognize that some substances involved in research laboratories are new compounds and have not been subjected to testing for carcinogenicity.  The following references that can be used to determine which substances are select carcinogens.

• OSHA Carcinogen List
• Annual Report on Carcinogens published by the National Toxicology Program (NTP), including all of the substances listed as "known to be carcinogens" and some substances listed as "reasonably anticipated to be carcinogens" based on the below standard
• IARC Monographs on the Identification of Carcinogenic Hazards to Humans, including all of Group 1 "carcinogen to humans," and some in Group 2A “probably carcinogenic to humans” or 2B, "possibly carcinogenic to humans" based on the below standard
• For substances listed in either Group 2A or 2B by IARC or under the category “reasonably anticipated to be carcinogens” by NTP, to be considered a “select carcinogen” by OSHA, it must also cause statistically significant tumor incidence in experimental animals in accordance with any of the following criteria:
  • after inhalation exposure of 6-7 hours per day, 5 days per week, for a significant portion of a lifetime to dosages of less than 10 mg/m3;
  • after repeated skin application of less than 300 mg/kg of body weight per week;
  • after oral dosages of less than 50 mg/kg of body weight per day  

Regulated Carcinogens fall into a higher hazard class and have extensive additional requirements associated with them. The use of these agents may require personal exposure sampling based on usage. When working with Regulated Carcinogens, it is particularly important to review and effectively apply engineering and administrative safety controls as the regulatory requirements for laboratories that may exceed long term (8 hour) or short term (15 minutes) threshold values for these chemicals are very extensive.

9.11 Nanomaterials

9.11.1. Nanomaterials: Exposure standards have been proposed for only a limited number of engineered nanomaterials (e.g. carbon nanofiber, silver, titanium dioxide) in the US. However, none have been adopted as regulatory standards.  See  Table 5  for types of nanomaterials.

9.11.2. Until more definitive standards are developed based on the understanding of nanomaterial toxicology, and the potential health risks associated with handling nanomaterials, researchers should take a conservative approach when planning to work with nanomaterials, and where applicable, implement a combination of advisory engineering controls, work practices, and PPE to minimize potential workplace exposures.

9.11.3. A detailed Standard Operating Procedure (SOP) for working with nanomaterials should be written to provide guidance on appropriate work practices, engineering controls, personal protective equipment (PPE), and waste disposal practices depending on the risk level of a particular nanomaterial or process involving a nanomaterial.

9.11.4. For further information, see the “Nanotool kit: Working Safely with Engineered Nanomaterials in Academic Research Setting”, the National Institute of Occupational Safety & Health’s (NIOSH) “General Safe Practices for Working with Engineered Nanomaterials in Research Laboratories" and the NIOSH “Current Strategies for Engineering Controls in Nanomaterial Production and Downstream Handling Processes.”

Table 5: Common Nanomaterials

Table 6:  Nanomaterial Risk Category