Safety Office, Commissary Building
University of Waterloo
200 University Avenue West
Waterloo, Ontario, Canada N2L 3G1
Phone 519 888 4567 Ext. 33587
Fax 519 886 8082
Email: safety@uwaterloo.ca
Any chemical used in a laboratory should be handled with care and according to laboratory procedures. Before performing work involving chemicals, safe handling procedures and the chemical's Safety Data Sheets (SDS) must be reviewed. If mixing chemicals, the reactivity of each must be reviewed to avoid adverse chemical reactions. Chemicals are hazardous for many reasons.
Many chemicals used in laboratories may be toxic. Toxicity depends on the quantity, frequency and duration of exposure, or the dose. Toxic effects can be local (at the site of exposure) or systemic (at another site in the body), acute or chronic. When dealing with toxic chemicals, it is important to consider the route of exposure and the target organ to ensure that proper controls are adhered to.
When planning and conducting experiments, it is critical to recognize that the combination of toxic effects of two or more substances may be significantly greater than that of one substance alone. Toxic reaction products can be much more dangerous than the starting reagents. Many cases of toxic reaction products occur when chemicals are mixed unintentionally. This can occur due to improper labelling, mishandling of chemicals and spills.
Laboratory workers must be able to recognize the potential hazards present to prevent exposure to toxic chemicals, and in the event of accidental exposure, know the procedures for emergency, spill response and first aid.
"All substances are poisons; there is none which is not a poison. The right dose differentiates a poison" (Paracelsus)
The single most important factor that determines whether a substance is harmful is the relationship between the amount/concentration and the toxic effect it produces. This is referred to as the dose-response relationship. Many chemicals are toxic with one small exposure, while others require repeated doses (chronic exposure). It is important to remember that this relationship is unique to each chemical.
The toxicity of a chemical is best identified by its lethal dose 50 (LD50). LD50 is defined as the amount of a chemical that when given to a specified laboratory animal (e.g. rat), it will kill 50% of the animals. The LD50 is usually expressed in mg/kg or g/kg of body weight. Thus, chemicals with low LD50's are highly toxic, requiring a low dose to cause fatal effects. For chemicals where the hazard is inhalation, the LC50 (lethal concentration 50), which is the concentration of chemical in air, is more often used. LC50 is usually expressed in ppm, mg/L or mg/m3. This information is found on the MSDS.
The duration and frequency of exposure are factors in whether a chemical will produce a toxic effect. While effects can occur after a single dose (acute), or with intermittent (repeated), or long-term (chronic) exposures, the specific chemical and route of entry determine the effect. Some chemicals are acutely toxic, while others require repeated exposures or have long-latency effects (effect appears long after the exposure).
Generally, the longer the duration and/or frequency of exposure, the greater the toxic effect. For certain chemicals, the body is able to eliminate the toxins and/or repair tissues to some degree, thus the time between exposures will also affect the total dose required for a response.
Ingestion - Refers to exposure by entrance through the mouth and swallowing. The substance enters the gastrointestinal tract and is absorbed into the system through the blood stream. Ingestion is a method of exposure that is highly preventable through use of proper personal protection equipment, personal hygiene practices and adherence to rules regarding eating, drinking and use of cosmetics in the lab.
Inhalation - Gases, vapours, aerosols, particulates, fibers and dusts can enter the body and cause either local or systemic effects by absorption through the mucous membranes in the mouth, throat and lungs.
For gases, the most important factor in rate of absorption is solubility. Chemicals that are highly soluble easily penetrate the lung tissue and blood, which allows them to be transported to other organs. For solids, particle size determines where a particle can penetrate and how far into the respiratory tract it can travel. Solubility of the particle (fat or water-soluble) also determines whether it will be cleared from the body, or remain for long periods of time causing chronic or long-latency disease.
A major factor in inhalation is the vapour pressure of the chemical - the higher the vapour pressure, the greater the potential of it being released into the air. It is also important to remember that vapour pressure increases with temperature, therefore by heating a substance, the likelihood that hazardous vapours will be produced increases. Procedures to control the production or release of airborne toxins are important to prevent both acute and chronic exposures. Ventilation through the use of fume hoods is the key control measure in preventing inhalation exposure. It is also necessary to reduce the surface area of solvents exposed, to cover containers, and to follow procedures to avoid spills.
Absorption - Can occur through intact or broken skin, or via a body orifice (e.g. eye, ear). Either the skin itself may be injured, or the chemical may be absorbed into the body and transported via the bloodstream. Use of PPE such as lab coats, gloves and goggles are the best method of protection against absorption.
Injection - Needles, razor blades, broken glass or other sharp objects that pierce the skin can allow toxic chemicals or biohazardous agents to enter the body. Proper handling and disposal of sharps is necessary to eliminate this method of exposure.
A maximum of 300 L of combustible (class II and III) and flammable liquids (class I), of which no more than 50 L can be flammable (class I), can be outside of a flammable liquid storage cabinet at any one time.
A maximum of 500 L of combustible (class II and III) and flammable liquids (class I), of which no more than 250 L can be flammable (class I), can be stored in an approved flammable liquid storage cabinet. Each lab is permitted a maximum of 3 flammable liquid storage cabinets.
All work, research, investigations, etc. involving flammable or combustible liquids must be carried out in an approved chemical (fume) hood when:
Flammable liquids can be easily ignited, even at concentrations less than their lower flammable limits, and at temperatures below their flash point. Vapours may be heavier than air, thus allowing them to travel long distances along the ground where they may reach an ignition source.
Part IV (s.4.12) of the Ontario Fire Code governs quantities of flammable liquids that are handled or stored in Laboratories. All laboratories must conform to these requirements.
Section 4.12.3.1(1) of the Ontario Fire code states:
The container size used for the storage of flammable or combustible liquids in a laboratory shall be not more than 5 L capacity.
Where refrigerators are required to keep flammable liquids (class I) at a controlled temperature the refrigerator must:
Description | Class | Boiling point (°C) | Flash point (°C) |
---|---|---|---|
Flammable | IA | < 37.8 | < 22.8 |
Flammable | IB | > 37.8 | < 22.8 |
Flammable | IC | --- | > 22.8 and < 37.8 |
Flammable | II | --- | > 37.8 and < 60 |
Combustible | IIIA | --- | > 60 and < 93.3 |
Combustible | IIIB | --- | > 93.3 |
Part IV of the Ontario Fire Code restricts dispensing flammable or combustible liquids from containers of more than 5 L capacity. Dispensing flammable or combustible liquids from containers of 5 L capacity or less is permissible in laboratories at University of Waterloo (UW) provided the dispensing is performed in an approved chemical (fume) hood. Chemistry Stores (ESC 109) is the only location on campus that has been designed and approved to dispense flammable or combustible liquids from containers with greater than 5 L capacity.
Oxidizing agents represent a significant hazard in the laboratory due to their capacity to undergo violent reactions when they come into contact with reducing agents, causing ignition in flammable and combustible materials. Oxidizers can also increase the intensity of a small fire, making safe storage a key consideration in the lab. In addition to the risk of fire, oxidizers may release toxic gases either by reacting with other chemicals, or through decomposition caused by heating. Oxidizers on their own can also have corrosive properties.
Oxidizers may be found in both solid and liquid form. Solid oxidizing agents such as metallic chlorates, perchlorates, nitrates, chromates and permanganates may form explosive mixtures with oxidizable dusts and other suspended particles (e.g. flour, coal dust, magnesium powder, zinc dust, carbon powder).
Liquid oxidizers include nitric acid, chromic acid and sulphuric acid. In addition to being oxidizers, these are also corrosive chemicals. One of the most hazardous liquid oxidizers is perchloric acid, and should be avoided if possible. If perchloric acid must be used, workers must be trained in safe handling procedures and a perchloric acid fume hood designed and constructed for this purpose must be used.
Corrosive materials include chemicals that will result in an immediate, acute erosive effect on tissue as well as other materials. Corrosive chemicals include strong acids and bases, dehydrating and oxidizing agents, and halogen gases.
When handling corrosive chemicals, the eyes and skin are most commonly at risk, however failure to use proper protective equipment and handling procedures can result in exposures to the respiratory and digestive tract through inhalation and ingestion as well.
Corrosive chemicals exist in solid, liquid and gaseous forms. Some examples and their effects are:
Corrosive solids Sodium hydroxide, phosphorous, phenol. Dust from these can be inhaled and cause serious damage to the respiratory tract.
Corrosive liquids - Bromine, sulfuric acid, aqueous sodium hydroxide, hydrogen peroxide. The danger in liquid form is the speed at which the liquid reacts upon contact, causing immediate destruction of tissue.
Corrosive gases - Chlorine, ammonia, nitrogen dioxide, hydrogen chloride, formaldehyde. Exposure occurs through inhalation, causing damage to the lining of the respiratory tract and lungs.
Special consideration must be given to the use of hydroflouric acid or hydrogen flouride. It should be avoided if at all possible, and if used, workers must be trained in safety procedures, first aid, and spill response. Specific procedures for hydrogen flouride are below.
Hydrofluoric acid is highly corrosive and toxic even in a dilute form, therefore any contact with skin or eyes must be treated as a medical emergency. The following procedures will assist the user in the safe handling of hydrofluoric acid. Further information is available from the Safety Office.
The following equipment is to be used when handling hydrofluoric acid:
Any laboratory possessing hydrofluoric acid must have:
Safety Office Recomendations for Hydrofluoric Acid Spill Station
When water-reactive chemicals come into contact with water, one or more of the following reactions can occur:
These materials must be stored away from any source of water or moisture. Some examples include:
Aqua regia (hydrochloric acid/nitric acid mixture) and piranha (sulfuric acid/hydrogen peroxide) solutions are both highly aggressive (corrosive) acids as well as being strong oxidizers. On top of this aqua regia is a solution that continually breaks down (off-gasses) to form fumes of nitrogen peroxide. Both solutions must be prepared in quantities for immediate use only and then disposed of immediately when the work is done. As the solutions are unstable, they should not be prepared and stored for future use and should never be stored in a sealed container, especially a glass one. When preparing and using the solution, it should be done in an open top beaker in a fume hood to allow for off-gassing. Please be aware that there is a large amount of heat (exothermic) generated in the making of these solutions so appropriate PPE must be worn (gloves/goggles/face shield/apron) and ensure there is an eye face wash/drench hose or an eyewash/shower combination available within 10 seconds of travel, and pathway free of obstructions that may inhibit the use of equipment. For disposal of these solutions, they should be diluted by adding the solution slowly to water (dilute by at least 10 times the original quantity, 20 times is recommended) and then neutralized using sodium bicarbonate or a solution of sodium hydroxide to a pH of 5. At this point, the solution can be safely poured down the drain with copious amounts of water, unless there are any hazardous materials still in solution (ie. heavy metals). For further information, contact the Safety Office at ext. 35755.
Pyrophoric chemicals will ignite spontaneously upon contact with air due to the extreme rate of oxidation. These must be stored under inert gas or mineral oil or other hydrocarbon liquids. Metals, when finely divided are pyrophoric. Some examples of pyrophoric materials are:
See section on organic peroxides under oxidizers.
An explosive is any chemical compound or mechanical mixture that, when subjected to heat, impact, friction, detonation, or other suitable initiation, undergoes rapid chemical change, evolving large volumes of highly heated gases that exert pressure on the surrounding medium. This term applies to materials that either detonate or deflagrate.
Explosives are regulated by the Canadian Explosives Act and Ontario Fire Code regulations, and any use, handling or storage must conform to these regulations.
Picric acid is a common reagent used mainly in biological laboratories. The hazard related to picric acid is dehydration- when it dries, it becomes a dangerous explosive. In addition, when in contact with metal, picrate salts can be formed, which are highly shock-sensitive. The following safety precautions must be adhered to:
**If dehydrated picric acid is discovered, contact the Safety Office at ext. 36268 for disposal.
Safety Office, Commissary Building
University of Waterloo
200 University Avenue West
Waterloo, Ontario, Canada N2L 3G1
Phone 519 888 4567 Ext. 33587
Fax 519 886 8082
Email: safety@uwaterloo.ca
The University of Waterloo acknowledges that much of our work takes place on the traditional territory of the Neutral, Anishinaabeg and Haudenosaunee peoples. Our main campus is situated on the Haldimand Tract, the land granted to the Six Nations that includes six miles on each side of the Grand River. Our active work toward reconciliation takes place across our campuses through research, learning, teaching, and community building, and is centralized within our Office of Indigenous Relations.