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POLLUTION FROM DIESEL FUMES
Arising out of the consideration of my annual report for the year 1971, I was requested to report
more fully on the question of atmospheric pollution from diesel fumes. The following is the substance
of the report I submitted to the Health Committee in February 1973. The subject falls naturally into
two main sub-headings, viz., Road Traffic and Railways.
(a) ROAD TRAFFIC
The Council has no statutory responsibilities for the control of air pollution arising from road
traffic. The Ministry of Transport and the Police are responsible for the enforcement of the Road
Traffic Act and the Regulations made thereunder. Amending Regulations applying to diesel vehicles
came into force in June, 1972. The Motor Vehicles (Construction and Use) (Amendment)
Regulations 1972 require that no avoidable smoke or visible vapour shall be emitted. In addition, a
driver must not be able to operate the excess fuel device, for easier starting, whilst the vehicle is in
motion, unless such device does not cause any increase in smoke or visible vapour. This should
ultimately eliminate the practice of lorry drivers tampering with the excess fuel device to gain more
power and thereby producing dense black smoke. After 1st April 1973, a compression - ignition
engine must be so constructed that it complies with the British Standard Specification for maximum
opacity of smoke.
The diesel engine is far more efficient than the petrol engine in that, except when starting from
cold, there is, theoretically, always more than sufficient air to ensure complete combustion of the
fuel.
Broadly speaking it can be said that a diesel engine tends to emit more smoke than a petrol
engine and about the same amounts of oxides of nitrogen, but it emits less hydrocarbons and
aldehydes and very much less carbon monoxide (between 0.1 and 1%). A properly maintained and
adjusted diesel engine emits no visible smoke and virtually no carbon monoxide. The sulphur content
of diesel oil is quite low, averaging 0.3%. Diesel smoke in quantity is dirty and nauseating but
research has not shown that it has any direct ill-effects on health. The petrol engine, in comparison is
a more prolific and insidious source of pollution, producing up to 6% of carbon monoxide which is
invisible.
In this country a great deal of research on the health effects of motor vehicle emissions has been
carried out by the Medical Research Council and other bodies and is still continuing. The Department
of the Environment has recently commissioned a study to extend up to five years in five city centres,
and in London a site in Cromwell Road, Kensington, has been selected. The behaviour of various
pollutants will be investigated and the extent to which motor vehicle exhaust is contributing to the
general urban pollution will be assessed.
The Scientific Branch of the Greater London Council has continued to make measurements of
pollution by spot tests and by continuous monitoring. Recent results have confirmed that, in general,
the levels of pollution in London streets fall within what are currently considered to be medically
acceptable limits. One such investigation was carried out by the Greater London Council in 1970
following a complaint of increased exhaust fumes in Batchelor Street, N.1, arising from the
Barnsbury Traffic Scheme. The results showed carbon monoxide concentrations to be low, usually
between 0 and 5 parts per million (by volume) and the highest value recorded was 10 ppm. Daily
averages of smoke varied from 40 to 270 microgrammes per cubic metre. In the opinion of the
Scientific Adviser the results gave little cause for complaint.
In view of the lead organo-metallic additives used in petrol, a three year exercise was conducted
by my department from 1968-1970 to measure the atmospheric lead contamination in Upper Street.
The average lead content varied from 0.2 to 1.5 microgrammes per cubic metre of air. Based on a
suggested American standard of 6 microgrammes per cubic metre, these results did not suggest any
danger from that source.
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