Lead-free petrol may be villain in mystery of demise of the world's most familiar bird

A A A

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.

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 compulsory.

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. 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 is strong.

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 the same.

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 of time.

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 12.

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."

PROMOTED VIDEO
Have you tried new the Independent Digital Edition apps?
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
iJobs Job Widget
iJobs General

Tradewind Recruitment: KS2 Teacher

Negotiable: Tradewind Recruitment: My client is a two form entry primary schoo...

Tradewind Recruitment: English Teacher

Negotiable: Tradewind Recruitment: My client is an excellent, large partially ...

Tradewind Recruitment: Science Teacher

£90 - £140 per day: Tradewind Recruitment: I am currently working in partnersh...

Tradewind Recruitment: Year 3 Primary Teacher

£100 - £150 per day: Tradewind Recruitment: Year 3 Teacher Birmingham Jan 2015...

Day In a Page

Isis hostage crisis: The prisoner swap has only one purpose for the militants - recognition its Islamic State exists and that foreign nations acknowledge its power

Isis hostage crisis

The prisoner swap has only one purpose for the militants - recognition its Islamic State exists and that foreign nations acknowledge its power, says Robert Fisk
Missing salvage expert who found $50m of sunken treasure before disappearing, tracked down at last

The runaway buccaneers and the ship full of gold

Salvage expert Tommy Thompson found sunken treasure worth millions. Then he vanished... until now
Homeless Veterans appeal: ‘If you’re hard on the world you are hard on yourself’

Homeless Veterans appeal: ‘If you’re hard on the world you are hard on yourself’

Maverick artist Grayson Perry backs our campaign
Assisted Dying Bill: I want to be able to decide about my own death - I want to have control of my life

Assisted Dying Bill: 'I want control of my life'

This week the Assisted Dying Bill is debated in the Lords. Virginia Ironside, who has already made plans for her own self-deliverance, argues that it's time we allowed people a humane, compassionate death
Move over, kale - cabbage is the new rising star

Cabbage is king again

Sophie Morris banishes thoughts of soggy school dinners and turns over a new leaf
11 best winter skin treats

Give your moisturiser a helping hand: 11 best winter skin treats

Get an extra boost of nourishment from one of these hard-working products
Paul Scholes column: The more Jose Mourinho attempts to influence match officials, the more they are likely to ignore him

Paul Scholes column

The more Jose Mourinho attempts to influence match officials, the more they are likely to ignore him
Frank Warren column: No cigar, but pots of money: here come the Cubans

Frank Warren's Ringside

No cigar, but pots of money: here come the Cubans
Isis hostage crisis: Militant group stands strong as its numerous enemies fail to find a common plan to defeat it

Isis stands strong as its numerous enemies fail to find a common plan to defeat it

The jihadis are being squeezed militarily and economically, but there is no sign of an implosion, says Patrick Cockburn
Virtual reality thrusts viewers into the frontline of global events - and puts film-goers at the heart of the action

Virtual reality: Seeing is believing

Virtual reality thrusts viewers into the frontline of global events - and puts film-goers at the heart of the action
Homeless Veterans appeal: MP says Coalition ‘not doing enough’

Homeless Veterans appeal

MP says Coalition ‘not doing enough’ to help
Larry David, Steve Coogan and other comedians share stories of depression in new documentary

Comedians share stories of depression

The director of the new documentary, Kevin Pollak, tells Jessica Barrett how he got them to talk
Has The Archers lost the plot with it's spicy storylines?

Has The Archers lost the plot?

A growing number of listeners are voicing their discontent over the rural soap's spicy storylines; so loudly that even the BBC's director-general seems worried, says Simon Kelner
English Heritage adds 14 post-war office buildings to its protected lists

14 office buildings added to protected lists

Christopher Beanland explores the underrated appeal of these palaces of pen-pushing
Human skull discovery in Israel proves humans lived side-by-side with Neanderthals

Human skull discovery in Israel proves humans lived side-by-side with Neanderthals

Scientists unearthed the cranial fragments from Manot Cave in West Galilee