Chemical Hazard Class Definitions – Stanford Environmental Health & Safety

Carcinogens

Summary: The risks associated with the use of laboratory chemicals must be well understood prior to their use in an experiment. As many chemicals have multiple hazards, ensure to review the safety guidance for all hazard classes that may apply.

Definition:
Carcinogens are chemicals or physical agents that cause cancer or tumor development, typically after repeated or chronic exposure. Their effects may only become evident after a long latency period and may cause no immediate harmful effects.

Further, Cal/OSHA (8 CCR 5191) defines a “select carcinogen” as a substance or agent that meets one of the following criteria:

It is regulated by Cal/OSHA as a carcinogen.
It is listed under the category, “known to be carcinogens” in the Annual Report on Carcinogens published by the National Toxicology Program (NTP)(latest edition); or
It is listed under Group 1 (“carcinogenic to humans”) by the International Agency for Research on Cancer (IARC)
It is listed in either Group 2A or 2B by IARC or under the category, “reasonably anticipated to be carcinogens” by NTP, and causes statistically significant tumor incidence in experimental animals in accordance with any of the following criteria:
1. 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;
2. After repeated skin application of less than 300 mg/kg of body weight per week; or
3. After oral dosages of less than 50 mg/kg of body weight per day.

Examples:
Carcinogens used in Stanford University laboratories include: Methylene chloride, benzene, formaldehyde, and acrylonitrile.

Compressed Gases

Definition:

Per 29 CFR 1910.1200 App B, a compressed gas is defined as a gas stored at pressures of 29 psi gauge or higher, which remains wholly gaseous at -50°C (-58°F). Related classifications include liquefied gases and dissolved gases, which are defined as follows:

Liquefied gas: A gas, stored at pressures of 29 psi gauge or higher, which is partially liquid at temperatures above -50°C (-58°F).
Dissolved gas: A gas which is dissolved in a liquid solvent at pressures of 29 psi gauge or higher.

Characteristics:

Compressed gases have inherent pressure hazards and can also create health hazardous and/ or flammable atmospheres.

Compressed gases may also be flammable, toxic, and/or corrosive. Some gases (i.e., silane, diborane, phosphine) are considered pyrophoric (will ignite spontaneously in air).

One additional hazard property common to all compressed gases is the substantial volume expansion that occurs when they are released into the air. Gas release in an inadequately ventilated room can create an oxygen-deficient environment.

Examples:

Compressed gas: Nitrogen, argon, helium, oxygen, hydrogen
Liquefied gas: Chlorine, carbon dioxide, nitrous oxide, dichlorane, hydrogen bromide
Dissolved gas in Solution: Acetylene

Information on Toxic Gases:
For additional information on gases classified as toxic gases and management responsibilities, go to https://ehs.stanford.edu/reference/toxic-gas-ordinance-tgo-data-table

Corrosive Materials

Summary:The risks associated with the use of laboratory chemicals must be well understood prior to their use in an experiment. As many chemicals have multiple hazards, ensure to review the safety guidance for all hazard classes that may apply.

Definition:

Corrosive materials cause irreversible destruction of living tissue through chemical action at the point of contact. As corrosive chemicals can be liquids, solids, or gases, corrosive effects most commonly affect the skin, eyes, and respiratory tract.

Examples:
Corrosive materials used in Stanford University laboratories include: Liquids such as acids and bases, bromine, and hydrogen peroxide; gases such as chlorine and ammonia; and solids such as phosphorous and phenol.

Hydrofluoric Acid:
For work with hydrofluoric acid, see SU’s Information on Hydrofluoric Acid.

Cryogenic Liquids

Summary:The risks associated with the use of laboratory chemicals must be well understood prior to their use in an experiment. As many chemicals have multiple hazards, ensure to review the safety guidance for all hazard classes that may apply.

Definition:
Cryogenic liquids are materials with extremely low boiling points (i.e. less than -150 °F/-101 °C).Characteristics:

One special property of both cryogenic liquids and dry ice is that they undergo substantial volume expansion upon evaporation or sublimation, which can potentially lead to an oxygen deficient atmosphere where ventilation is limited.

Some cryogenic liquids can also pose additional hazards including toxicity and flammability (i.e. liquid carbon monoxide).

Examples:
Cryogenic liquids used in Stanford University laboratories include: liquid nitrogen, liquid helium, and liquid argon.

Flammable and Combustible Liquids

Summary:The risks associated with the use of laboratory chemicals must be well understood prior to their use in an experiment. As many chemicals have multiple hazards, ensure to review the safety guidance for all hazard classes that may apply.

Definition:
For the purposes of laboratory safety, both flammable and combustible liquids are considered fire hazards. Flammable liquids have a flash point of less than 199.4 °F (93 °C) and combustible liquids have a flash point above 199.4 °F (93 °C).

The flash point of a substance is the temperature at which enough substance will vaporize to form an ignitable mixture with air.

Examples:
Flammable and combustible liquids used in Stanford University laboratories include: acetone, methyl alcohol, acetic acid, toluene, and glycerol.

Highly Acutely Toxic Chemicals

Summary:The risks associated with the use of laboratory chemicals must be well understood prior to their use in an experiment. As many chemicals have multiple hazards, ensure to review the safety guidance for all hazard classes that may apply.

Definition:
Categorized based on their LC₅₀ or LD₅₀ values, substances with a high degree of acute toxicity have the ability to cause adverse effects after a single exposure/dose or multiple exposures/doses within a 24 hour period. Many of these chemicals may also be characterized as toxic gases, Select Agent Toxins, corrosives, irritants, or sensitizers.On GHS-compliant Safety Data Sheets (SDSs), highly acutely toxic chemicals can be identified via the following hazard statements:

H300: Fatal if swallowed
H310: Fatal in contact with skin
H330: Fatal if inhaled

Examples:
Highly acutely toxic chemicals used in Stanford University laboratories include: Acrolein, Arsine, Nitrogen dioxide.

Highly Reactive/Unstable Materials

Definition:
Highly reactive and unstable materials are those that have the potential to vigorously polymerize, decompose, condense, or become self-reactive under conditions of shock, pressure, temperature, light, or contact with another material. Examples of such substances are explosives, peroxides, water-reactives, and pyrophorics.Examples:

Explosives: Lead azide, nitroglycerin
Peroxide formers: Isopropyl ether, sodium amide, diethyl ether, styrene
Water Reactives:Alkali metals (lithium, sodium, potassium), calcium carbide
Pyrophorics:Grignard reagents (RMgX), metal powders (e.g., Al, Co, Fe, Mg, Mn, Pd).

Irritants

Definition:
Irritants are substances that cause reversible effects (e.g., swelling or inflammation) on skin or eyes at the site of contact. A wide variety of organic and inorganic compounds are irritants; thus, skin and eye contact with all laboratory chemicals should be avoided.

Reproductive Toxins

Definition:
Reproductive toxins are substances that adversely affect reproductive capabilities. Possible effects include chromosomal damage (mutations), effects on fetuses (teratogenesis), adverse effects on sexual function and fertility in adult males and females, as well as adverse effects on the development of the offspring. Many reproductive toxins cause damage after repeated low-level exposures. Effects become evident after long latency periods.

Reproductive Toxins List:
Under CA Proposition 65, the State of California maintains a list of known chemicals causing reproductive toxicity. For the updated list, refer to: https://oehha.ca.gov/proposition-65/proposition-65-list#files

Examples:
Chemicals that are reproductive or developmental hazards include: chloroform, benzene, arsenic, and mercury compounds.

Stanford University’s Reproductive & Developmental Health Protection Program:
Personnel planning to use reproductive toxins can get more health-related information and further consultation via: https://ehs.stanford.edu/topic/health-wellness/reproductive-and-developmental-health-protection.

Restricted Chemicals

Stanford University Restricted Chemicals:
If not properly considered, managed, and overseen, the use of certain chemicals can result in conditions of higher risk for laboratory personnel and to facilities.List:
Laboratory personnel may not use any of the following chemicals in Stanford University laboratories without obtaining prior written approval from their PI or Lab Supervisor:

Toxic gases regulated by Santa Clara County (e.g., diazomethane, hydrogen cyanide, hydrogen fluoride (anhydrous), nickel carbonyl)
Dimethylmercury

Granting Prior Approval:
For additional information on methods for granting prior approval, go to section 5.2 of the Chemical Hygiene Plan.

Sensitizers

Summary:The risks associated with the use of laboratory chemicals must be well understood prior to their use in an experiment. As many chemicals have multiple hazards, ensure to review the safety guidance for all hazard classes that may apply.

Definition:
A sensitizer is a substance that can cause exposed people to develop an allergic reaction in normal tissue after repeated exposure to the substance. The reaction may be as mild as a rash (contact dermatitis) or as serious as anaphylactic shock.Examples:
Compounds that may cause sensitization in some individuals include diazomethane, various isocyanates, formaldehyde, and benzylic and allylic halides.