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The Expert Panel on Air Quality Standards (EPAQS) has concluded in the light of further scientific evidence that the current health based UK standard for 1,3-butadiene in urban air should remain 1 part per billion (2.25 micrograms per cubic metre) measured as a running annual mean.

The Panel believes that concentrations of 1,3-butadiene in the ambient atmosphere of 1 part per billion constitute so small a risk to the population as to be undetectable by any feasible study.

Notes for editors

Expert Panel on Air Quality Standards (EPAQS)

The Expert Panel on Air Quality Standards (EPAQS) was set up by the Secretary of State for the Environment in 1991 to advise the Government on air quality standards. The Chair, Professor Anthony Seaton CBE, Head of Environmental and Occupational Medicine at the Liberty Safe Work Research Centre within Aberdeen University retired in 2002. Members of EPAQS are drawn from the fields of medicine and air pollution. Applications for the Chair and several new members of EPAQS are currently being considered.

Terms of Reference

The terms of reference for the Expert Panel on Air Quality Standards are:

"To advise the Secretary of State for the Environment, Scottish Ministers, the National Assembly for Wales and Department of the Environment in Northern Ireland as required, on non-occupational ambient air quality standards, with particular reference to the levels of airborne pollutants at which no or minimal effects on human health are likely to occur:

i. taking account of the best available evidence of the effects of air pollution on human health and of progressive development of the air quality monitoring network; but

ii. without reference to the practicality of abatement or mitigation measures, the economic costs and economic benefits of pollution control measures or other factors pertinent to the management rather than the assessment of risk;

Where appropriate, for example for pollutants where no threshold for adverse effects can be determined, the Panel may wish to recommend exposure-response relationships or other information which Government might use to set policy objectives.

to identify gaps in the knowledge needed for standard setting and suggest potential priority areas for future research;

to advise on other aspects of air quality and air pollution referred to it;

for the purpose of informing the development of policy on the improvement of air quality and increasing public knowledge and understanding of air quality issues."

The Panel's recommendation

In its 1994 report, the Panel accepted that 1,3-butadiene is a genotoxic carcinogen. The new evidence supports this view, and this therefore remains the Panel's opinion. The Panel has earlier stated as a principle in recommending Air Quality Standards that concentrations of genotoxic carcinogens should not be allowed to rise above those currently attained.

This principle formed the basis of the Panel's 1994 recommendation of 1 part per billion. Its starting point was a conclusion, based on the then available literature, that it was unlikely that an excess risk of leukaemia or lymphoma could be detected in workers exposed to concentrations lower than 1000 part per billion over a working lifetime. The Panel then divided this figure by 100 to allow for the difference between a full lifetime and that part spent at work and also for a range of susceptibility in the population (EPAQS, 1994). The Panel was however, unanimous in agreeing that the levels of genotoxic carcinogens in the environment should not be allowed to rise. It noted that the concentrations of 1,3-butadiene measured in urban air of the United Kingdom had not exceeded 1 part per billion as a running annual average. The Panel therefore recommended 1 part per billion, measured as a running annual average, as the Standard and were of the view that, at this concentration, any risks to the health of the population were exceedingly small.

Since the 1994 report was written, urban background concentrations have dropped considerably and more data are now available at kerbside locations. In addition, much more detailed data have been produced on cohorts of workers potentially exposed to 1,3-butadiene. The analysis of these further data has given a firmer base to the Panel's earlier conclusion that 1000 part per billion is an appropriate starting point for the derivation of an air quality standard, increasing our confidence in our recommendation for an Air Quality Standard of 1 part per billion.

The Panel believes that concentrations of 1,3-butadiene in the ambient atmosphere of 1 part per billion constitute so small a risk to the population as to be undetectable by any feasible study. It concludes that this should remain the Air Quality Air Quality Standard for the UK.

1,3-Butadiene

The majority of 1,3-butadiene in ambient air comes from combustion sources, for example, road transport (85% of the total emissions) - primarily from petrol with a small contribution from diesel-fuelled vehicles. The introduction of catalytic converters in 1991 has had a significant impact on the emissions from road transport causing a reduction of 56% in total emissions from 1990 to 1999. It is also an important industrial chemical, being used particularly in the manufacture of synthetic rubber for tyres. Fugitive emissions from the manufacture and use of 1,3-butadiene in the chemical industry are small.

The Report

The EPAQS Second Report on 1,3-Butadiene is available from The DEFRA Publishing Unit, ISBN 0-85521-010-9, priced £7. This is a review document on the UK Air Quality Standard for 1,3- butadiene. It is one in a series by the Expert Panel on the principal pollutants. Earlier reports have covered airborne particles, polycyclic aromatic hydrocarbons, lead, nitrogen dioxide, particles, sulphur dioxide, carbon monoxide, 1,3-butadiene, ozone and benzene. The report will shortly be available on the Panel's website

Air Quality Strategy

The Air Quality Strategy was published on 19 January 2000 (DETR Press Notice 032 refers). The Strategy sets out air quality objectives to be achieved by at least 2005 (these are set with reference to air quality standards which represent no or minimal risk of health effects to the public). The pollutants covered are benzene, 1,3 butadiene, carbon monoxide, lead, nitrogen dioxide, ozone, particles (PM10) and sulphur dioxide. The objectives for seven of the pollutants are now in regulation for the purposes of Local Air Quality Management.

The objective for 1,3-butadiene is 2.25 micrograms per metre cubed measured as a running average annual mean to be achieved by the end of 2003.

The Strategy also describes a range of policy options for achieving the objectives and the contribution to be made at international, national and local levels in key sectors - industry, transport and local Government.

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