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Hazardous Chemicals

NFPA4.jpgChemicals pose health and safety hazards to personnel due to innate chemical, physical, and toxicological properties. Chemicals can be grouped into several different hazard classes. The hazard class will determine how similar materials should be stored and handled and what special equipment and procedures are needed to use them safely. 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. More detailed hazard information for specific chemicals can be found by referencing the SDS for that chemical.

There are numerous posting and labeling methodologies including the National Fire Prevention Association (NFPA) building and/or door placarding that provides an overview of the key chemical hazards contained within that building or room. NFPA postings have the familiar four color 1-4 number rating, which quickly supplies the hazard information broken down into four hazard classes, with 1 indicating a low level of hazard and 4 indicating a high hazard level. The four chemical hazard types correspond to the four color areas: red indicates a flammability hazard, yellow indicates a reactive hazard, blue indicates a health hazard and the white area is reserved for special hazards that are identified by hazard symbols or labels to indicate hazards such as radioactivity, biohazard, water reactive chemicals, etc. Each of these hazards has a different set of safety precautions associated with them. 

1. Flammability and Combustibility Hazards

flameSM.pngA number of highly flammable substances are in frequent use in campus laboratories. Flammable liquids include those chemicals that have a flashpoint of less than 100 degrees Fahrenheit (°F), and combustible liquids have a flashpoint between 100-200 °F. These materials must be stored in flammable storage cabinets if aggregate quantities of 10 gallons/room or more are stored in the lab. Guidance on proper flammable liquid storage is provided in a FireNet from UC Davis Fire Prevention. Flame-resistant laboratory coats must be worn when working with large volumes of flammable materials (>1L) and/or with procedures where a significant fire

 risk is present (e.g., when working with open flame, etc.). These materials pose a significant risk and should be treated with care, even though use of these materials is fairly common in the laboratory setting. Particular attention should be given to preventing static electricity and sparks when handling flammable liquids.

It is the vapors from flammable liquids that burn, rather than the liquids themselves. For a fire to occur, there must be: 1) vapor concentration between the lower and upper flammability limits; 2) source of oxygen (often air); and 3) an ignition source. Careful handling and use of chemical fume hoods are typically sufficient to prevent high vapor concentrations. Do not use open flames where flammable vapors may be present. Ensure that containers are properly bonded and grounded before transferring flammable liquids between metal containers or equipment.

2. Reactivity and Stability Hazards

explosives.pngReactive and unstable substances are materials which may decompose, condense, vigorously polymerize, or become self-reactive under conditions of shock, temperature, pressure, light, or contact with other materials, with the release of large volumes of gas or heat. Examples of such chemicals include explosives, pyrophorics, peroxides, and water-reactive chemicals. These substances pose an immediate hazard and procedures for their use and storage must be carefully reviewed and followed. Such materials must also be stored in a manner to protect from light, heat, shock, friction, static discharge, contact with a catalyst, or other conditions to which they are sensitive. Some materials, such as peroxide formers, may not be explosive, but may form explosive substances over time.

Pyrophoric chemicals are a special classification of reactive materials that spontaneously ignite when in contact with air and require laboratory-specific training. Flame-resistant (FR) laboratory coats must always be worn when working with pyrophoric chemicals. Individuals working with pyrophoric materials must know the appropriate method(s) to quench the chemicals being used. Additional information related to pyrophoric and water-reactive materials is provided in SafetyNet #135 – Procedures for Safe Use of Pyrophoric/Water Reactive Reagents. Helpful safety videos on reactive and pyrophoric chemicals are available from the Dow Chemical Company, and for organolithium chemicals from Yale University.

3. Oxidizers

oxidizerSM.pngOxidizers present a fire and explosion hazard when they come in contact with flammable or combustible materials. They can: 1) speed the development of a fire and increase intensity, 2) cause substances which are normally stable in air to rapidly burn, and 3) lead to spontaneous combustion of materials without an obvious ignition source. Oxidizers are classified on a scale of 1-4 by the NFPA based on their potential to initiate spontaneous combustion. In addition to the flammability hazards posed by oxidizers, they can also be corrosive or toxic.


4. Health Hazards

Cal/OSHA uses the following definition for health hazard in 8 CCR §5191:

poisonSM.gif“A chemical that is classified as posing one of the following hazardous effects: Acute toxicity (any route of exposure); skin corrosion or irritation; serious eye damage or eye irritation; respiratory or skin sensitization; germ cell mutagenicity; carcinogenicity; reproductive toxicity, specific target organ toxicity (single or repeated exposure); aspiration hazard.”

Criteria by which a specific chemical is classified as a health hazard can be found in 8 CCR §5194, including the definition of a “simple asphyxiant.” An overview of the major classes of “hazardous” and “particularly hazardous substances” and their related health and safety risks are detailed below.

a. Corrosive Substances

corrosiveSM.pngAs a health hazard, corrosive substances cause destruction of, or alterations in, living tissue by chemical action at the site of contact.

Major classes of corrosive substances include:

  • Strong acids – e.g., sulfuric, nitric, hydrochloric and hydrofluoric acids;
  • Strong bases – e.g., sodium hydroxide, potassium hydroxide and ammonium hydroxide;
  • Dehydrating agents – e.g., sulfuric acid, sodium hydroxide, phosphorus pentoxide and calcium oxide; and
  • Oxidizing agents – e.g., hydrogen peroxide, chlorine, bromine, perchloric acid, and nitric acid.

Symptoms of exposure for inhalation include a burning sensation, coughing, wheezing, laryngitis, shortness of breath, nausea, and vomiting. For eyes, symptoms include pain, blood shot eyes, tearing, and blurring of vision. For skin, symptoms may include reddening, pain, inflammation, bleeding, blistering and burns. As a physical hazard, corrosive substances may corrode materials they come in contact with and may be highly reactive with other substances.

It is important to review information: 1). regarding the materials they may corrode, 2) their reactivity with other substances, and 3) on health effects. In most cases, these materials should be segregated from other chemicals and require secondary containment during storage.

b. Irritants

irritantsSM.pngIrritants are non-corrosive chemicals that cause reversible inflammatory effects on living tissue by chemical action at the site of contact. A wide variety of organic and inorganic compounds, including many chemicals that are in a powder or crystalline form, are irritants. Consequently, eye and skin contact with all laboratory chemicals should always be avoided. Smoke is a common example of an irritant which can irritate the nasal passages and respiratory system. Symptoms of exposure can include reddening or discomfort of the skin and irritation to respiratory systems.

c. Sensitizers

Danger.jpgA sensitizer (allergen) is a substance that causes exposed people to develop an allergic reaction in normal tissue after repeated exposure to the substance. Examples of sensitizers include diazomethane, chromium, nickel, formaldehyde, isocyanates, arylhydrazines, benzylic and allylic halides, many phenol derivatives, and latex proteins. Sensitizer exposure can lead to all of the symptoms associated with allergic reactions, or can exacerbate an individual’s existing allergies.

d. Hazardous Substances with Toxic Effects on Specific Organs

Substances included in this category include:

  • Hepatotoxins –substances that produce liver damage, such as nitrosamines and carbon tetrachloride;
  • Nephrotoxins –agents causing damage to the kidneys, such as certain halogenated hydrocarbons;
  • Neurotoxins – substances which produce their primary toxic effects on the nervous system, such as mercury, acrylamide and carbon disulfide;
  • Agents which act on the hematopoietic system – e.g., carbon monoxide and cyanides which decrease hemoglobin function and deprive the body tissues of oxygen; and
  • Agents which damage lung tissue – e.g., asbestos and silica.
    Personnel working with these materials should review the SDS for the specific chemical being used, and take special note of the symptoms of exposure.

e. Particularly Hazardous Substances

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

    1. Hazardous chemicals; and
    2. Particularly hazardous substances.

Substances that pose such significant threats to human health are classified as "particularly hazardous substances". The Cal/OSHA “Laboratory Standard” (8 CCR §5191) requires that special provisions be documented in laboratory SOPs to prevent the exposure of laboratory personnel to PHSs, including:

  1. Establishment of designated areas;
  2. Use of containment devices (e.g., fume hoods, glove boxes);
  3. Procedures for contaminated waste disposal; and
  4. Decontamination procedures.

Particularly hazardous substances are divided into three primary types.

1. AcuteToxins

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. Many of these compounds can also be classified as corrosives, irritants, sensitizers, toxic gases, Select Agent Toxins, or specific-organ toxins.

2. ReproductiveToxins

Reproductive toxins include any chemical that may affect the reproductive capabilities, including chromosomal damage (mutations), effects on fetuses (teratogenesis), and adverse effects on sexual function and fertility. 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, personal physician, and EH&S before working with substances that are suspected to be reproductive toxins. SafetyNet #108 – Pregnancy and Reproductive Hazards in the Workplace: Chemical and Radiological Hazards provides additional information on this subject.

3. Carcinogens
Carcinogens are chemical or physical agents capable of causing cancer or tumor 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.

Comprehensive UC Davis requirements related to carcinogens is provided in the UC Davis Chemical Carcinogens Manual. Please consult this manual for detailed information. SafetyNet #139 – Guidelines for Handling Formaldehyde and SafetyNet #140 - Guidelines for Handling Dichloromethane (Methylene Chloride) provide information specific to formaldehyde and dichloromethane respectively. Contact EH&S for additional information on carcinogens and campus requirements.

f. Nanomaterials

The increasing use of nanomaterials in research laboratories warrants consideration of the hazards they may pose. As is the case with many new technologies, the health effects of nanomaterials have not been thoroughly investigated. Consequently, the uncertainty surrounding the toxicity of nanomaterials merits a cautious approach when working with them.

Nanomaterials include any materials or-9particles that have an external dimension in the nanoscale (~1 – 100 nanometers, 10 meter). Nanomaterials occur naturally in the environment, are products of incomplete combustion, and are produced via chemical synthesis. Synthesized nanomaterials are referred to as Engineered Nanomaterials (ENMs). Materials whose properties do not differ significantly between their nanoscale and larger forms are generally excluded from ENMs. Some examples of ENMs include fullerenes (carbon buckey- balls), carbon nanotubes, carbon nanofibers, quantum dots, and metal oxide nanoparticles.

Nanomaterials can be categorized by the risk of potential exposure they pose to personnel based on the physical state of the materials and the conditions in which they are used. In general, the risk of exposure is lowest when nanomaterials are bound in a solid matrix with little potential to create airborne dust or when in a non-volatile liquid suspension. The risk of exposure increases when nanomaterials are used as fine powders or are suspended in volatile solvents or gases. The parent compound of the nanomaterial should also be taken into consideration when evaluating the potential hazards associated with exposure (e.g., a highly toxic compound such as cadmium should be anticipated to be at least as toxic and possibly more toxic when used as a nanomaterial). Laboratory personnel using or preparing nanomaterials must utilize a combination of engineering controls, SOPs, and personal protective equipment to minimize potential exposure to their self and others.

The UC Davis Chemical and Laboratory Safety Committee has adopted the detailed guidance related to nanomaterials from the California Nanosafety Consortium of Higher Education’s “Nanotoolkit: Working Safely with Engineered Nanomaterials in Academic Research Settings” and the National Institute of Occupational Safety & Health’s (NIOSH) “Safe Practices for Working with Engineered Nanomaterials in Research Laboratories”. A useful video on nanoparticle safety is available from the Dow Chemical Company. Given the uncertainty of the health and environmental hazards posed by nanomaterials, SOPs are required for the preparation, use, storage, and disposal of nanomaterials. All nanomaterials, including solutions containing nanomaterials, are to be disposed as hazardous waste. SafetyNet #132 - Nanotechnology: Guideliness for Safe Research Practices has been prepared to provide additional guidance on these materials. Contact for additional information if needed.

g. Compressed Gases & Cryogenic Liquids

Compressed gases and cryogenic liquids present pressure and asphyxiation hazards in the workplace. Both compressed gases and cryogenic liquids may also present additional health hazard and/or flammability concerns. Given these hazards, special handling and storage requirements must be followed to mitigate the associated risks. More detailed information on compressed gases can be found in SafetyNet #60 - Compressed Gas Safety, while additional information on cryogenic liquids is contained in SafetyNet #58 - Safety Precautions for Cryogenic Liquids.