Working safely with solvents

Exposure to solvents can affect your health in many ways. In some circumstances, the effect can be very serious, therefore you must control the risks from exposure to potentially harmful solvents.

Within UCL there is a large range of solvents used as standard and even more chemicals that are used as experimental solvents.

Types of solvents

Organic solvents (containing carbon)

Hydrocarbon solvents are aliphatic and aromatic, such as benzene or petrol
Oxygenated solvents such as alcohols, ketones, aldehydes, esters, glycol etheres, etc
Halogenated solvents such as dichloromethane (Chlorinated and brominated hydrocarbons)

Inorganic non-aqueous solvents

These are solvents other than water, that are not organic compounds. Common examples are liquid ammonia, liquid sulphur dioxide, phosphoryl chloride and pure sulphuric acid. Water is classed as an inorganic solvent as its chemical structure does not contain carbon.

Hazards relating to solvents

No matter what the solvent is, it is important to remember to assess the hazards associated with the chosen solvent, as well as those associated with the other chemicals involved in the experiment.

Health risks from solvents

Solvents may enter the body through inhalation or through the skin. Due to their low vapour pressure, the health risks they pose can be realised easily.

Use the solvent Safety Data Sheet as guidance for hazards, storage, use and waste.

Physical risks

Although these chemicals are used for their properties as solvents, it must not be forgotten that they are hazardous chemical in their own right and can react violently when mixed with other chemicals including other solvents.

Due to this solvent waste must be separated from other waste and in separate solvent waste streams, for example, Chlorinated and Non-chlorinated waste.

Examples of hazards

Flammable - Most organic solvents
Explosive - Nitromethane, ether residue (peroxide formation)
Narcotic - Ether, chloroform
Carcinogenic - Dichloromethane, benzene
Mutagenic - teratogenic Toluene, ethanol
Toxic - Methanol, carbon disulfide
Chronic conditions - such as contact dermatitis and workplace asthma
Acute conditions - such as irritation of the skin, eyes and lungs, headaches, nausea and dizziness.

Exposure limits

A major risk of solvent use is its volatility (low boiling point) causing flammable or toxic vapour.

Some general information on solvent properties demonstrates that possibility.

The exposure limits are the maximum amount you may legallly be exposed to in an 8 hour period (long-term limit), or in a 15-minute period (short-term limit).

The explosive limit is the percentage of vapour that will generate a flammable mixture with air. When working with small small volumes and in a fume cupboard or with an LEV this is not relevant. Outside an LEV/fume cupboard or on a large scale a Dangerous Substance and Explosive Atmosphere Regulations (DSEAR) risk assessment may be required.

View common solvent chemical limits

Solvent	Melting point oC	Boiling Point oC	Flash Point oC	Explosive limits %GHS label	Exposure limits short term/long term
Acetone -94.7	56.1	-20.7	2.6-12.8	Flammable Irritant	500 ppm/ 1500 ppm
Acetic acid	16	118	40	Apr-16	Flammable Corrosive
Acetic anhydride	-73.1	139.8	49	2.7-10.3	Flammable Irritant Corrosive
Acetonitrile	-46	81	2	4.4-16.0	Flammable Irritant
Butanol	-89.8	117.7	35	1.45-11.25	Flammable Corrosive Irritant
t-Butanol	25	82	11	2.4-8.0	Flammable Irritant
Benzene 5.5	80.1	-11.6	1.2-7.8	Flammable Irritant Health Hazard	1 ppm/ Carcinogenic
Chloroform	-63.5	61.2	non-flammable	Irritant Health Hazard	2 ppm/ Absorbed through skin
Cyclohexane	6.5	80.7	-20	1.3-8	Flamm. Irritant Environ. Hazard
Dichloromethane	-96.7	39.6	above 100	Irritant Health Hazard	100 ppm/ unknown
Diethyl ether	-116.3	34.6	-45	1.9-48.0	Flammable Irritant
DMF	-60.5	152	58	2.2-15.2	Flammable Irritant Health Hazard
DMSO	19	189	89	2.6-42	Flammable Irritant Health Hazard
Ethyl acetate	-83.6	77.1	-4	2.0-11.5	Flammable Irritant
Ethanol	-114.1	78.2	16.6	3.3-19	Flammable Irritant
Hexane	-96	68.5	-26	1.2-7.4	Flamm. Irritant Health/Environ. Hazard20 ppm/ not reported
Isopropanol	-89	82.6	11.7	2.2- %	Flammable Irritant
Methanol	-97.6	64.7	11	6.7-36.0	Flammable Health Hazard Toxic
Pentane	-130.5	35.9	-49	1.4-7.8	Flamm. Irritant Health/Environ. Hazard600 ppm/ not reported
THF	-108.4	66	-14	2.0-	Flammable Irritant Health Hazard
Toluene	-95	111	6	1.2-7.1	Flammable Irritant Health Hazard
Xylene	-47.4	138.5	30	1.1-6.6	Flammable Irritant Health Hazard

Good Practice

Eliminate - Substitute hazardous solvents with less toxic or hazardous solvents Carry out a risk assessment before using any solvent for the first time and show why that solvent is the best to use both for safety and for the experiment.
Minimise - Solvents evaporate quickly, so lids should be properly replaced on storage vessels / Winchesters immediately after use. Do not decant in open-top vessels, and when designing the experiment, minimise the risk of evaporation of the solvent as far as reasonably practicable. This includes solvent-based products, including paints, and cleaning substances.
Always have good ventilation - For some substances, the odour threshold exceeds legal exposure limits. Therefore, if you can smell chloroform, benzene, carbon tetrachloride and dichloromethane, you may be overexposed. Always check to see if the solvent has defined workplace exposure limits (WELs). When working with solvents, know whether the solvent readily forms a hazardous vapour. The risks may require that there is good ventilation or a requirement for forced ventilation.
PPE - This is only to be used in addition to all the other control measures. If reusable PPE is chosen such as RPE with filters, a documented procedure on how RPE is stored and needs to be available and followed.

Waste solvents

It is necessary for solvent waste to be classified either according to their own properties or by the chemical that they have been used in conjunction with.

Each work area needs to plan for the removal of waste before generating it, and reassess the requirements when a new project is started in the work area.

The most common solvent is water, but as with most solvents, after it has been used in an experiment it will be contaminated with the reactants / products from the experiment and will need to be either “cleaned” or sent to the correct waste stream.

All labs / departments should have a waste management plan which will require a section for solvents.

The following information is required:

The types of solvents used in the laboratory that may produce waste
The processes and operations that may produce waste solvents.
The types of waste solvents produced (e.g. contamination).
Any specific hazards associated with waste solvents.
The quantities of waste solvents generated.

It should be noted that if a laboratory produces or holds 500 kilograms or more of hazardous waste in any 12-month period, it must register the laboratory with the Environment Agency.

Risk groups when dealing with waste solvents

When dealing with waste solvents, as well as the risk to the users and others in the work area, the following risk groups have to be taken into account.

The environment - staff (porters / contractors) involved in the removal of waste from the work area
The waste carrier

Management of waste solvents

Once the manager for the work area has the above information, a waste management plan for the solvents can be written.

This will depend on the information from the first section but will cover;

Waste Segregation - Is waste separated into appropriate categories? Are staff members made aware of segregation requirements and arrangements?
Containers - Are appropriate receptacles used for the storage? Are the containers sensibly located and suitably labelled?
Waste Handling - Are hazardous waste solvents handled in a safe manner with due attention to any associated hazard? Are contractors handling waste informed of the dangers?
Storage Areas - How and where are the waste solvents stored? How long are solvents stored prior to transport and disposal?
Procedures - How do we meet our duty of care under environmental legislation? What emergency procedures are in place in the event of an unwanted incident?
Safety - Are employees made aware of the hazards of the waste solvents? Are adequate safety equipment and systems provided?