WORKING FOR A HEALTHY FUTURE

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

Diesel engine exhaust emissions and lung cancer

John Cherrie

Summary…

• Diesel engines and their emissions• Guidance from HSE• Original concerns about cancer• The epidemiological evidence• The International Agency for Research on Cancer

(IARC) classification• The likely impact on the working population• Exposures and how they are changing• Possible changes to the EU Carcinogens Directive

Diesel…

• Rudolf Diesel invented the engine in 1893

• Uses the heat from compressing the fuel air mixture to initiate ignition

• Widely used for heavy duty applications but increasingly in cars

• There are probably about 400,000 people occupationally exposed to diesel engine exhaust in Britain

Diesel cars in Europe…

Emissions…

• Are a complex mixture:• Soot (carbon)• Water• Carbon monoxide• Oxides of nitrogen and sulphur• Polycyclic aromatic hydrocarbons (PAHs)• Various other substances

• Elemental carbon commonly used as a marker of exposure

SulphatesMetalsHydrocarbonsCarbon

HSE guidance (2008)…

• Irritation of the eyes and respiratory tract• Coughing, increasing breathlessness and

increased sputum production• Limited evidence for lung cancer

• Good source of guidance for control of exposure in fixed workplaces e.g. garages

http://www.hse.gov.uk/pubns/priced/hsg187.pdf

Toxicological evidence for cancer risk…

• In 1988 IARC reviewed animal experimental evidence• Five well conducted studies - chronic exposure of rats to

high concentrations of whole diesel exhaust• Most showed tumours in the lungs• Two studies with filtered exhaust showed no effect

• Concluded that there was sufficient evidence to conclude diesel exhaust emissions were carcinogenic in animal toxicology• Limited evidence from human epidemiological studies

Epidemiological evidence…

• Studies among non-metal miners, railroad workers and workers in the trucking industry • Best studies take account of smoking risks

• Many (most) studies show increasing risk of lung cancer with increasing exposure• Overall risks increased by about 50% for

prolonged occupational exposure

• Some studies also suggest an increased risk for bladder cancer

Lung cancer risk and exposure…

Silverman et al. The Diesel Exhaust in Miners Study: A Nested Case-Control Study of Lung Cancer and Diesel Exhaust. Journal of the National Cancer Institute.

Data from a study of non-metal miners in the USA

The IARC evaluation…

• Latest evaluation June 2012• Concluded diesel engine exhaust is

“carcinogenic to humans” (Group 1) • There is “strong evidence” for the ability of

whole diesel-engine exhaust to induce cancer in humans through genotoxicity

• Recognised that new technology diesel engines have reduced emissions but insufficient information to classify them differently

Occupational cancer in Britain…

5.3% (4.6 – 6.6%)

Men = blueWomen = red

Cancer registrations…

85% of the cancer cases come from the top ten chemical agents

- excluding ETS, which is already banned

800 cases of lung and bladder cancer per year

Exposures and how they are changing…

In the future we expect exposure levels to decrease by about 7% per annum because of replacement of old engines with new technology

The European dimension…

• The European Commission is considering revising the Carcinogens Directive to include Diesel Exhaust Emissions (as elemental carbon)• Which would result in it being highlighted in

COSHH

• They may also set an Occupational Exposure Limit (OEL)• Existing limits are around 100 mg/m3

• An effective limit would be nearer 10 to 20 mg/m3

Exposures and how they are changing…

In the future we expect exposure levels to decrease by about 7% per annum because of replacement of old engines with new technology

OEL?

OEL?

OEL?

Greater control of exposure is needed…

• Use of local exhaust ventilation and good general ventilation in garages and similar workplaces

• Replacement of old engines• Filtration of air into vehicle

cabs• Use of respirators for mobile

workers, e.g. traffic wardens

Summary…

• Diesel engine exhaust particulate causes lung cancer

• There are many people exposed at work (and in the urban environment)

• Relatively large numbers die as a consequence of their exposure

• We need to need to tighten exposure controls