ABC of Safety in the Biological Sciences

 

 

CARCINOGENIC CHEMICALS

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:

• Absorption through the respiratory system by inhalation of dust, vapour or both.
• Absorption through the skin from contact with spillage's or splashes, or from contact with contaminated clothing, benches, apparatus and floors.
• Ingestion from contaminated hands or food. Pipetting by mouth should never be allowed.
• Absorption through the eye membranes from dust, vapours or splashes.

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:

• Rubber, P.V.C. or polythene disposable gloves.
  • Buttoned laboratory coats or preferably wrap around gowns which tie at the back.
  • Laboratory safety glasses, or a full face safety shield if the possibility of a splash exists.
    • An approved respirator with a suitable particulate vapour cartridge.

Treatment
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.

Chemicals:
acetaldehyde
amino azobenzene
2-acetylaminofluorine
acrylonitrile
acryl amide
adriamycin
aflotoxins
p-amino azobenzene
0-aminoazotoluene
4-aminobiphenyl
arsenic and arsenic compounds
benzene
benzidine
benzidine based dyes
benzidine derivatives
beryllium
beryllium compounds
bis(chloromethyl) ether
cadmium
cadmium compounds
carbon tetrachloride
chlorambucil
chloroform
4-chloro-o-toluidine
chromic potassium sulphate
chromium compounds
chromium trioxide
cisplatin
cobalt chloride
cyclophosphamide
daunomycin
2,4-diaminoanisole
2,4-diaminotoluene
di aniline derivatives
1,2-dibromoethane
1,2-dibromo-3-chloropropane
dichlorobenzene
dichloroethane
dichloromethane
diepoxybutane
diethyl sulphate
diethyl hydrazine
dimethyl formamide
dimethyl hydrazine
dimethylcarbamoyl chloride dimethyl sulphate
dioxane
epichlorohydrin
epoxides
1,2-epoxy propane
ethylene dibromide
ethylene oxide
ferrous sulphate
formaldehyde
formic acid
hexamethylphosphoramide
hydrazine
hydrazine sulphate
lead and lead compounds
lead acetate
naphthylamine
nickel
nickel compounds
nitroso compounds
perchloric acid
polycyclic aromatic hydrocarbons
potassium bromate
potassium chromate
potassium dichromate
sodium chromate
sodium dichromate
sodium nitrite
styrene
styrene oxide
tannic acid
o-toluidine
treosulphan
tris(2,3-dibromopropyl) phosphate
vinyl chloride

Dyes:
acid fuchsin
auramine O
basic fuchsin
crystal violet
dihydroxyphenylalanine
eosin Y
fast blue B
fast blue salt R
fast garnet GBC
fast green
fast red TR
gentian violet
Giemsa
light green SF
magenta
methyl violet
nigrosine
pararosaniline
patent blue V
ponceau De Xylidine
ponceau 2R
ponceau 3R
resorcin fuchsin
Sudan III
Sudan IV
trypan blue

The following chemicals and dyes have not yet been classified but are considered to have a high hazard potential:
acridine orange
aniline and its bi-products
benzoyl chloride
benzoyl peroxide
benzyl acetate
brilliant blue FCF
carbazole
catechol
ferric oxide
hydrogen peroxide
hydroquinone
isopropyl alcohol
methyl acrylate
methyl methacrylate
methyl red
orange G
polyethylene
polyvinyl pyrrolidone
propylene
resorcinol
rhodamine B
scarlet red
selenium and its compounds
Sudan 1
Sudan II
Sudan red
trichloroethane

Destruction and disposal of carcinogenic waste
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.

 

 

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REFERENCES