Inside vehicles
Benzene has been measured in air inside vehicles at levels higher than those in residential air , but substantially lower than those at petrol filling stations . 4
Food and water
Waterborne and foodborne benzene contributes only a small percentage of the total daily intake in non-smoking adults . 2
World Health Organization ( WHO ) benzene guidelines
Drinking-water
0.01 mg / l ( guideline values corresponding to the upper 95 % confidence limit of modelled excess lifetime cancer risks of 10 −4 , 10 −5 and 10 −6 are 0.1 , 0.01 and 0.001 mg / l , respectively ). 5 , 6 An excess lifetime cancer risk of 10 −4 , 10 −5 or 10 −6 means the risk of one new cancer case above background levels per 10 000 , 100 000 or 1 million people , respectively .
Air
No specific guideline value has been developed for air . Benzene is carcinogenic to humans , and no safe level of exposure can be recommended . For general guidance , the concentrations of airborne benzene associated with an excess lifetime risk of leukaemia of 10 −4 , 10 −5 and 10 −6 are 17 , 1.7 and 0.17 μg / m 3 , respectively . 4
Health effects
Acute effects
� Acute occupational exposure to benzene may cause narcosis : headache , dizziness , drowsiness , confusion , tremors and loss of consciousness . 2 Use of alcohol enhances the toxic effect . 7
� Benzene is a moderate eye irritant and a skin irritant . 2
Effects following chronic exposure �
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Benzene is a well-established cause of cancer in humans . 1 , 3 The International Agency for Research on Cancer has classified benzene as carcinogenic to humans ( Group 1 ). 1 , 3 Benzene causes acute myeloid leukaemia ( acute non-lymphocytic leukaemia ), and there is limited evidence that benzene may also cause acute and chronic lymphocytic leukaemia , non-Hodgkin ' s lymphoma and multiple myeloma . Individuals who have experienced benzene poisoning requiring treatment show a substantially increased risk of mortality from leukaemia . 3
Chronic exposure to benzene can reduce the production of both red and white blood cells from bone marrow in humans , resulting in aplastic anaemia . 2
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Both B-cell proliferation and T-cell proliferation are reduced by benzene . Decreased host resistance to infection has been reported in several laboratory animals exposed to benzene . However , other measures of immunotoxicity have not been studied . 2