Hazardous Chemicals
Please read these related areas on this site: Waste Disposal and Chemical Information.
Chemicals in the organic lab can be flammable, volatile, health hazardous, and/or corrosive. In the organic chemistry lab courses at CU, we require that you know the hazards of all the chemicals in the laboratory. First and foremost, you need to know these hazards so that you will know when it is critical to take precautions such as wearing protective clothing or keeping chemicals from flame. We consider this so important that you will always be asked to look up the hazards and include them in your prelab notebook write-up, and we will put questions about chemical hazards on the prelab quizzes.
Not only does the CU Chem Department think that chemical hazard information is essential knowledge, it is a federal law (below). Whether you work in the medical field, photography, construction, retail stores, painting, etc., chemicals will be in the workplace and you have the right to know the hazards of the chemicals that are present. We hope that the lessons you learn about the hazards of chemicals will enable you to work in a safe manner whatever your future profession.
Chemical Bottle Labels
The two major systems of chemical hazard labeling are NFPA (National Fire Protection Agency) and HMIG (Hazardous Material Information Guide). Each uses the same color and number codes, but each lays the label out in a different manner:

The NPFA is concerned primarily with fire, HMIG with safety in general. Also, the manufacturer assigns the number value when they label and sell a compound, rather than the government. Therefore, number values will change from manufacturer to manufacturer according to their individual interpretation of the hazard. You can find these numbers on the MSDS for a compound.
Toxicology
Several different terms are used to quantify how toxic a substance is under different circumstances. These are listed below.
Term | Subscript | Definition | Usage | Description |
LD | Lo, 50 | Lethal dose | Exposure by any route except inhalation | LD50 is the single dose of a toxic substance administered by any route (other than by inhalation) that causes the death of 50% of an animal population. LDLo is the lowest dose of a substance reported to have caused death in humans or animals. |
LC | Lo, 50 | Lethal concentration | Exposure by inhalation | LC50 is the concentration of a material in air that kills 50% of a group of test animals when administered as a single exposure in a specific time period (usually 1 hour). LC values are often expressed as parts of material per million parts of air (ppm). |
TD | Lo, 50 | Toxic dose | Exposure by any route except inhalation | TDLo is the lowest dose of a substance reported to produce any toxic effect in humans or to produce tumorigenic or reproductive effects in animals or humans. Like LD, it is used for all routes of administration except inhalation. The same subscripts, routes of administration, and species tested abbreviations are used as with LD and LC. TD50 is toxic dose 50, and means that 50% of the test subjects suffered from one or more toxic effects. |
TC | Lo, 50 | Toxic concentration | Exposure by inhalation | TCLo is the lowest concentration of a substance in air to which humans (or animals) have been exposed for any given period of time that has produced any toxic effect or produced a tumorigenic or reproductive effect one or more members of the group of subjects. TC values are only for the inhalation toxicity of a compound. TC values are of great importance to industrial workers and chemists exposed to fumes and dust. |
TLV | TWA, STEL, C | Threshold limit value | Airborne concentration allowed in a normal work schedule | TLV and PEL are exposure limits and are used by agencies to establish permissible exposure limits in workplaces. TLV is threshold limit value and is used by the American Conference of Governmental Industrial Hygienists (ACGIH) to express the maximum airborne concentration of a material to which most workers can be exposed during a normal daily and weekly work schedule without adverse effects. Values for TLV and PEL are usually equivalent; each is the average concentration of a chemical in the air to which most people can be exposed and show no ill effect. These values are sometimes derived from TCLo values. A PEL or TLV value refers only to inhalation toxicity, not to skin or eye contact or to ingestion. Not all TLVs have been established by scientific experimentation. Many are estimates, based on experience with the chemical or based on known information about similar chemicals. TLVs are expressed in three ways:
|
PEL | TWA, STEL, C | Threshold limit value | Airborne concentration allowed in a normal work schedule | PEL is the permissible exposure limit and is used by the Occupational Health and Safety Administration (OSHA). It is usually equivalent to TLV. |
Some approximate toxicities are listed below. The Human Dose column lists how much compound a 150 pound adult human would have to ingest to reach the LD50.
LD50 (animal) | Human Dose | Toxicity | Value in NFPA or HMIG |
0-50 mg/kg | 0-1 tsp | Extreme | 4 |
50-500 mg/kg | 1 tsp to 1 oz | High | 3 |
500-5000mg/kg | 1 oz to 1 pt | Moderate | 2 |
5-15 g/kg | 1 pt to 1 qt | Slight | 1 |
Over 15 g/kg | More than 1 qt | Practically non-toxic | 0 |
Other Hazards
- Carcinogen: a substance that causes cancer. Officially, a compound must be labeled as a carcinogen if it is identified as such in the latest edition of one of three lists: the National Toxicology Program (NTP) Annual Report on Carcinogens, the International Agency for Research on Cancer (IARC) Monographs, or OSHA 29 CFR1910, Subpart Z, Toxic and Hazardous Substances. Informally, compounds are called carcinogens if they are on the NTP or IARC lists of known or suspected carcinogens, the California List or on the list of the EPA Carcinogen Assessment Group.
- Teratogen: a compound that can cause fetal damage.
- Allergen: a compound that can cause allergic reactions.
- Lachrymator: a compound that causes tearing of the eyes.
- Contact hazard: usually expressed in descriptive word form:
- Irritant means that it causes a reversible inflammatory effect on living tissue.
- Corrosive means that the chemical causes visible destruction of tissue if it comes into contact with skin.
- Sensitizer means that with repeated exposures it causes a substantial proportion of exposed people to develop an allergic reaction.
The Law
The Occupational Safety and Health Administration (OSHA) requires employers to meet the requirements of the Hazard Communication Standard (HCS: 29CFR 1910.1200). The main points of this HCS as they pertain to students in the teaching labs are:
- Students must have access to a list of all the chemicals present in the laboratories.
- Material Safety Data Sheets (MSDS) must be made available for each chemical in the lab.
- Chemical containers must be properly labeled and their hazards must be listed.
- Students must be trained in the proper handling of the chemicals.
- Complete information about the OSHA requirements is available on the Internet. The organic chemistry Web site lists pertinent links.
The Organic Chemistry teaching labs comply with these regulations by doing the following:
- A print out of the database inventory is on the blue cabinet in the organic chemistry stockroom (Ekeley M1B48).
- Hazard information for all chemicals used in the labs is available in the Handbook for Organic Chemistry Lab.
- MSDS are available in printed form in big notebooks on top of the blue cabinet in the organic chemistry stockroom, and in each student lab.
- All chemical containers are properly labeled.
- We train you, the student, in the proper handling of chemicals.
The links below will take you either to the laws on the OSHA site and to other university sites that explain these laws.
OSHA
- Table of Contents for regulations - table of contents for 29 CFR
- HC1910 - Table of contents for Occupational Safety and Health Standards, part 1910 of 29 CFR. Of special interest:
- HC1910.1200 - Regulations applying to the handling of toxic and hazardous substances in industrial situations.
- 1910.1200 App E - Employer Compliance Advisory or Chemical Hygiene Plan advisory.
- 1910.1450 - Occupational exposure to hazardous chemicals in laboratories.
- HC1910 - Table of contents for Occupational Safety and Health Standards, part 1910 of 29 CFR. Of special interest: