WORKING FOR A HEALTHY FUTURE

INSTITUTE OF OCCUPATIONAL MEDICINE . Edinburgh . UK www.iom-world.org

Benzene – Monitoring, Managing and Reducing the Risk

John Cherrie

Summary…

• Benzene and the diseases it causes• Sources in the workplace• Monitoring exposure

• Air monitoring• Biological monitoring• Modelling exposure• Skin exposure

• Risk assessment• The Occupational Exposure Limit for benzene

• Risk management

Benzene is…

• Benzene is an aromatic hydrocarbon• It is colorless, flammable with a

sweet smell• It was first isolated and identified in

1825 by Michael Faraday• It has had many varied industrial and

consumer uses• In the past it was even used as an after-

shave lotion because of its pleasant smell.

Mr Jones has leukaemia…

• He was diagnosed in 2010• Mr Jones worked offshore

for an oil company between 1990 to 2000

• He came into contact with natural gas and natural gas condensate

• These streams contain some benzene, e.g. 0.1 to 5% for condensate

Benzene is hazardous to health…

• It affects the blood forming system• Main adverse effects are various cancers from

long-term exposure• According to the International Agency for

Research on Cancer…• acute non-lymphocytic leukaemia

• Plus limited evidence it may also cause…• acute lymphocytic leukaemia• chronic lymphocytic leukaemia• multiple myeloma

• non-Hodgkin lymphoma

Sources in the workplace…

• Benzene was frequently used as an industrial solvent in the past

• Now it can be found in small quantities in…• gasoline • petrochemical streams – onshore and offshore• emissions from coke ovens and other similar

processes

• It may also be found in the wider environment at very low levels

Monitoring exposure…

• Air monitoring• Colorimetric detector tubes• Active pump-based systems• Diffusive samplers• Direct-reading instruments

• There are standard methods available from HSE

• Biological monitoring• Estimating exposure using simple models• Is there any risk from skin contact?

http://www.hse.gov.uk/pubns/mdhs/

Active samplers…

• A glass or metal tube containing an adsorbent material

• Air is drawn through the adsorbent by a pump

• Tube located close to workers nose/mouth

http://www.skcltd.com/

Diffusive sampling…

• Sometimes called “passive” samplers

• Simple container with an adsorbent material and a small air gap between inlet opening and the surface of the adsorbent

• Most commonly the adsorbent is activated charcoal

• Sampler worn on the lapel

Mr Jones…

• In 2000, HSE made about 250 measurements of occupational exposure to benzene during routine offshore oil and gas production operations

• 91% of measurements were less than 0.05 ppm 99% were less than 0.5 ppm, as 8-hr average

• Higher levels are measured during specific tasks, e.g. up to 10 ppm in opening valves, changing of filters, pipeline clean-out

Direct-reading monitors…

• For example, Photo-ionisation detector (PID)

• Results can show minute-by-minute fluctuations

• Data can be stored for later analysis• Generally respond to a range of

compounds, although some types can be relatively specific for benzene

• Care needed to get data relevant to exposure

http://www.raesystems.com/products/ultrarae-3000

Mr Jones…

• Measurements using a direct reading instrument ranged from zero to 200 ppm

• No information about where measurements made• No details of the duration of measurements

• Many measurements may have been made very close to leaks

• The limited information about the samples makes the data useless

Biological monitoring…

• Analysis of blood, urine or exhaled breath for benzene or its metabolites• e.g. urinary S-phenylmercapturic acid

• Samples should be collected before and after work

• Samples reflect difference between individuals, both in their exposure and the way they metabolise benzene

• Benzene is mostly eliminated from the body within about 24-hr

Quality assurance for measurements…

• Workplace Analysis Scheme for Proficiency (WASP)• http://www.hsl.gov.uk/centres-of-excellence/proficiency-t

esting-schemes/wasp.aspx

• Use an qualified and experienced person• http://www.bohs.org/education/professional/

• UK Accreditation Service• for sampling and analysis

Quality assurance for measurements…

http://www.ukas.com/TestingSearch.asp?qt=search+our+website

Exposure modelling tools…

• There are a number of model tools available to estimate workplace exposure• COSHH Essentials

www.hse.gov.uk/coshh/essentials • Stofenmanager

www.stoffenmanager.nl • Advanced REACH Tool (ART)

www.advancedREACHtool.com

Exposure modelling tools…

Skin exposure to benzene…

• Benzene may pass through the unbroken skin and contribute to systemic exposure

• Benzene is very volatile so splashes and spills onto the skin may evapourate

• Probably only a problem if the skin is occluded, e.g. spills inside gloves

• Solvents also damage the skin barrier and may cause dermatitis

Workplace Exposure Limits…

• Limits in the UK are published by the HSE, but mostly are now derived from European Indicative Occupational Exposure Limits• Specified over 8-hr and/or 15-min • Units of concentration parts per million

(ppm) or mg/m3

• Benzene limit unchanged since 2003• No biological monitoring guidance value

for benzene

EH40 entry for benzene…

Mr Jones…

• Overall his exposure was probably less than 1 ppm

• Background level <0.05 ppm• Average of the peak exposure levels…

5 x 1/8 = 0.625 ppm

• Risk was probably adequately controlled under COSHH Regulations

Principles of Good Control Practice……

• Minimise emission, release and spread of substances• Take into account all relevant routes of exposure• Control exposure by measures that are proportionate to

the health risk• Choose the most effective and reliable control options• Where needed provide suitable personal protective

equipment• Review regularly all elements of controls• Inform and train all employees • Ensure control measures does not increase overall risk

http://www.hse.gov.uk/coshh/detail/goodpractice.htm

Specific risk management for benzene

• Always use a fuel retriever when draining petrol tanks or pipelines

• Don’t blow out fuel lines with compressed air• Use protective gloves such as disposable

nitrile where there is a risk of short-term skin contact

Is there an important health problem?

• We have estimated the number of leukaemia deaths occurring in Britain from past exposure

• Risk estimates for acute non-lymphocytic leukaemia • RR = 2.17 for workers in industrial chemicals• RR = 1.32 for land transport• RR = 1.11 for low benzene exposure

• Using these data and estimates of the number of people exposed gives…

• 7 leukaemia cases per year due to benzene

Rushton L, Brown TP, Cherrie JW, et al. How much does benzene contribute to the overall burden of cancer due to occupation? Chem Biol Interact 2010;184:290–292.

Conclusions…

• Benzene is a known human carcinogen• There are about 20k people exposed to higher

levels and 700k to low levels• Monitoring exposure is relatively simple and and

methods are adequately standardised• Few people are likely to be exposed above the

current Workplace Exposure Limit• Very few people in Britain now get leukaemia

because of benzene exposure