ABC of Safety in the Biological Sciences
Carcinogenic chemicals are highly toxic. Rigorous care is needed when handling these chemicals, especially where threshold limits have not been established. Carcinogenic chemicals show large differences in dose requirements for the production of tumours in laboratory animals and there is little basis for comparing carcinogen potential between animal and human.37 Nevertheless if a chemical has produced malignant tumours in laboratory animals it must be regarded as being potentially hazardous to humans and handled accordingly. It is therefore essential that all of those in contact with these substances are fully aware of the extent and nature of the hazards associated with their use. These chemicals often have a delayed health effect and there is often uncertainty as to the threshold limit for humans.34 If possible, seek safer alternatives.
The World Health Organisations International Agency for Research on Cancer (IARC) has classified carcinogens into three groups as follows:
Category 1 Established human carcinogens. There is sufficient evidence to establish a causal relationship between human exposure to these agents and the development of tumours.
Category 2 Probable human carcinogens. Evidence, usually related to long term animal studies, suggests that human exposure may result in the development of tumours.
Category 3 Substances suspected of having a carcinogenic potential in humans. In these cases there is limited evidence from animal and epidemiological studies to suggest a hazard.
Exposure to carcinogenic chemicals can result from the following:
If possible designate a special area of the laboratory for handling carcinogenic chemicals and wash hands thoroughly before and after use. Other precautions which need to be taken are as follows:
1 Always use a fume hood. There must be, at the work point, a minimum of 0.60 metres per second air flow. The exhaust from the fume cupboard must not be fed back into the laboratory nor should it discharge where it might be hazardous to others.
2 The working surface where carcinogenic chemicals are handled must be non-absorbent so that any spill can be easily dealt with.
3 Always ensure that full protective clothing is worn. This should include:
For any accidental skin or eye contact the affected area should be washed immediately with cold water (not warm or hot) for at least 15 minutes until all evidence of the chemical has been removed. Warm or hot water encourages absorption of chemicals. Vapour from hot water may also carry chemical particles which can be inhaled. Use a safety shower if necessary and change clothing and shoes which need to be washed before re-use. Wash equipment separately from other laboratory apparatus.
Store carcinogenic chemicals in appropriately labelled, closed screw cap containers. Keep them apart from other chemicals and keep a documented record of their usage.
Some known or suspected carcinogens9
20 29 37
This is not a complete list. The exclusion of a chemical does not necessarily indicate that it is not a carcinogenic substance.
arsenic and arsenic compounds
benzidine based dyes
chromic potassium sulphate
di aniline derivatives
dimethylcarbamoyl chloride dimethyl sulphate
lead and lead compounds
polycyclic aromatic hydrocarbons
fast blue B
fast blue salt R
fast garnet GBC
fast red TR
light green SF
patent blue V
ponceau De Xylidine
The following chemicals and dyes have not
yet been classified but are considered to have a high hazard
aniline and its bi-products
brilliant blue FCF
selenium and its compounds
Destruction and disposal of carcinogenic
Organic compounds can be destroyed by sodium dichromate in a strong solution of sulphuric acid. One to two days is required for the total destruction of chemicals when a freshly prepared reagent is used. The residue can then be flushed to sewer with a large amount of water.
Carcinogens that readily oxidise can be inactivated by adding to a saturated solution of potassium permanganate in acetone. Concentrated or 50% aqueous sodium hypochlorite is also suitable as an oxidising agent.
Alkylating, arylating or acylating agents can be destroyed by reaction with nucleophiles such as water, hydroxyl ions, ammonia, thiols and thiosulphate. The reaction can be enhanced by dissolving the carcinogen in ethanol before treatment with the nucleophile.
Aflotoxins should be added to a hypochlorite solution followed by treatment with acetone to destroy any 2,3-dichloroaflotoxin B1 which may have been formed.
Cyclophosphamide can be destroyed by adding to potassium hydroxide dissolved in methanol.
Polycyclic aromatic hydrocarbons are readily oxidised using the sodium dichromate-sulphuric acid mixture as in 1.