- It would be a bitter irony indeed if the introduction
of lead-free petrol were behind the disappearance from British cities of
the house sparrow, the world's most familiar bird. But the circumstantial
evidence is so strong, according to the world authority on sparrows, Denis
Summers-Smith, that the hypothesis needs to be investigated urgently.
- The removal of lead compounds from motor fuel was one
of the biggest victories for the environment movement of the post-war period.
The compounds, used in petrol to boost its burning efficiency, had been
found to accumulate in children's bodies and gradually damage their brains.
After a long struggle by green campaigners, an official decision was finally
taken to phase out lead right across Europe. In 1988 unleaded petrol became
available at British service stations; on January 1 this year it became
- But what replaced the lead? Substitute chemicals involved
in boosting the petrol octane rating may have caused problems all of their
own, Dr Summers-Smith believes, and may present the answer to the biggest
environmental mystery of recent years why the house sparrow has vanished
from many of our big cities, virtually without trace.
- Dr Summers-Smith is an engineering consultant and former
senior scientific adviser to ICI. Now 79, he has been studying sparrows
intensively for more than 50 years and has produced four books on the birds,
including the standard monographs, The House Sparrow (1963) and The Sparrows
(1988), as well as numerous papers in learned journals. His own sparrow
database contains more than 5,000 items.
- Two substances associated with unleaded petrol in particular,
he feels, deserve urgent investigation MTBE (methyl tertiary butyl ether),
an additive, and benzene, a by-product of the refining. Both are toxic,
of health concern, and known to cause cancers in animals.
- There is a dearth of information on MTBE. (Not so, in
the US where the catastrophic consequences of MTBE are now fairly well-known.
- jr) The UK Petrol Industry Association cannot give a figure on how much
unleaded petrol contains it, though it is probably less than 50 per cent.
- The Department of Health, in an unpublished paper, signals
health concerns about MTBE and says measurements should be made of concentrations
in the air in Britain none are done at present. California and Denmark
currently plan to phase it out.
- Benzene is better known and a proven carcinogen. It is
thought to have become more prevalent with the uptake of the super unleaded
petrol grade, which was widely bought by motorists in the early 1990s.
The amount that can be present in petrol was cut from 5 per cent to 1 per
cent by an EU directive that came into force on 1 January this year.
- Dr Summers-Smith agrees that there is no scientific evidence
as yet linking MTBE or benzene directly with house sparrows.
- But he points out that the circumstantial evidence of
a connection between sparrow decline and the introduction of unleaded petrol
- For a start, he now believes that road traffic pollution
is at the bottom of the sparrow mystery. He does so because of a remarkable
discovery he has made after spending this summer analysing all the available
sparrow population data: British sparrow populations have indeed collapsed
in big cities but not in small towns.
- While he calculates the drop in cities such as London
or Glasgow is of the order of 95 per cent, in small towns such as Crewkerne
in Somerset or Guisborough in Cleveland the numbers have stayed virtually
- This is backed up by many of the letters in response
to The Independent's Save the Sparrow campaign.
- What cause of sparrow decline could operate selectively
in cities but not small towns? Hardly any, Dr Summers-Smith says: not predation
by cats and sparrowhawks, not disease, not lack of nesting places, not
competition for food. All would have similar effects in small as well as
in big conurbations.
- Only road traffic pollution, he says, would be of a different
order in cities, where a very much larger number of vehicles are present,
often with engines idling, pumping out fumes. It would not have to affect
the birds directly: it could, for example, cut down the number of insects
they need to feed their very young chicks, which as German researchers
have found, and the Independent reported last week, is the most vulnerable
point in the sparrows' lifecycle.
- Dr Summers-Smith then points out that the disappearance
of the sparrow and the introduction of unleaded correlate closely in terms
- Although sparrows have been gradually declining for much
of the past century, the real collapse of house sparrow populations in
places such as London, much evidence suggests, is a phenomenon of the 1990s.
In Kensington Gardens, for example, 885 birds were counted by ornithologists
in 1948; in 1966 there were 642 birds, and in November 1975 there were
544. But in February 1995 there were only 46, and in July 2000 there were
- Lead-free petrol use is also a 1990s phenomenon. When
it became available in Britain in 1988 at first it sold only in tiny amounts,
but it represented nearly 90 per cent of total fuel sales by the end of
last year, when leaded petrol was phased out completely.
- "While the removal of lead from petrol was unquestionably
right, could it be that it was at the cost of introducing other undesirable
materials to the environment?" Dr Summers-Smith asks.
- "There are at least two substances used in unleaded
petrol that are potentially hazardous MTBE and benzene. As the disappearance
of the house sparrow from our large cities correlates with the introduction
of unleaded petrol, the possibility that such substances are involved surely
requires immediate investigation if for no other reason than as an application
of the precautionary principle."
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