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Coming up for Air
by John Stuart Clark

Stuff a pipe over the exhaust of a idling car, stick the other end through a side light, settle down behind the steering wheel, and close all doors and windows. Within a couple of minutes you will be slumped against the Pearly Gates.

Failing that (though it never fails), stick the car in a sealed garage, open all the vehicle's orifices and rev the engine mercilessly. It has the same effect but takes a little longer, about ten minutes, just enough time to write a witty epitaph, or come to your senses and bust out.

The efficiency with which the effluence from a motor vehicle snuffs out life is a by-product of the inefficiency of the internal combustion engine. Its failure to burn off all the fossil fuel injected into it is a measure of its success as the country's prime polluter.

Too heavy, too powerful, under occupied and over used, the theoretical efficiency of a car cruising in perfect circumstances peaks at only 25%. In practice, few manage to convert more than 10% of fuel energy into motion.

At rest, grid locked or in a sealed garage, a running engine is little more than a highly efficient factory for the production of poisons, something the Nazis were quick to appreciate. Years before The Final Solution and Zyclon B, extermination camps employed jacked-up trucks to lethal effect.

The road lobby would condemn such an introduction as crass sensationalism, alarmist in the extreme. They would be right, but such is the nature of the beast. Their argument against the current concern for levels of traffic pollution starts from the premise that the air in our towns and cities is cleaner than a hundred years ago. Again, they are right, but somebody needs to remind them times have changed.

Britain is no longer the Workshop of the World, and the choking pea-soupers Sherlock Holmes stalked through have relocated to the Third World, banished by clean air legislation of the 1950s and 60s. What few production industries remain on this island cough up less than 12% of airborne pollutants. Domestic heating plants are slightly worse offenders, but the dirtiest kid on the block by a barge pole is transport, spewing out over 51% of the filth in the air.

The Environment Agency is not the meanest of watchdogs, more a poodle than a rottweiler, but even they have declared that road transport poses a greater risk to the UK than is imagined. Last year they dealt with 1,400 traffic pollution incidents, up 30% on the previous year. They conclude that its impact on air and water quality, the ecology, landscape, climate, flooding, property and health can only get worse.

Fresh air is an invigorating concoction, 78% nitrogen, 21% oxygen, with a dash of carbon dioxide, argon and various trace gases. Also present, depending on the weather and location, are minute particles of water vapour, ice crystals and dust (sand, pollen and plant spores).

Exhaust is a toxic cocktail of carbon monoxide, sulphur dioxide, oxides of nitrogen, benzene, toluene and xylene. There are also particles present, microscopic particulates of lead, other metals and 'petroleum coke' or soot, ranging in size from PM2.5s (the smallest of interest to researchers) up to PM10s (i.e. 10 microns).

What kills the suicide victim is carbon monoxide, a colourless, odourless, highly poisonous gas produced when carbon is burnt without sufficient oxygen to give off carbon dioxide. Entering through the walls of the lungs, carbon monoxide binds itself to the haemoglobin in the blood to create carboxyhaemoglobin, thus reducing the amount of haemoglobin available for carrying oxygen to the heart and brain. Inhale too much of the stuff and the body becomes drowsy, neuro-behavioural functions slow down, fall apart and finally stop.

Sulphur dioxide is a nasty irritant that exacerbates bronchitis and can induce chronic bronchitis. It constricts the airways and causes a tightening of the chest. Like nitrogen dioxide it is a serious threat to children and asthmatics. Oxides of nitrogen are also closely associated with hyperactivity and emphysema, but for all three gases there are safe levels that the body can cope with because they can be expelled.

There are no safe levels for benzene, toluene, xylene or the particulates. The gases add the smell to petrol and are known carcinogens. Benzene is implicated in over 5,000 new cases of cancer in the UK every year. It is so potent, its use in laboratories has been all but banned.

The particulates are microscopic bits of carbon which have absorbed heavy metals and carcinogens like asbestos. How they attack the body depends on the metal, but sufficient quantity of any or all of them can induce neurological disfunction and premature death. For example, lead in the blood stream impacts on several different parts of the body, particularly the nervous system and the brain.

While airborne and roadside levels of lead have dropped markedly since the introduction of unleaded petrol, low levels of exposure still take their toll, eventually. It is the cumulative effect of particulates that does the damage. Older people are particularly vulnerable, and become more so with age.

That is the cup of poison you will swim through tomorrow when you pedal off into town. Nobody questions that exhaust fumes are lethal. The evidence is piled high and has been for several decades. And nobody denies that all these pollutants have additional, lesser sources.

Where the argument lies is in the quantity we actually breathe in after the crap has mingled with fresh air, and how the diluted chemicals affect those exposed. The argument turns on the question of dispersion - whether the poisons are dispersed sufficiently to render them harmless.

Pantechnicans are good at spreading their fallout around, simply because their bulk initiates more air movements than cars, but the prime dispersant is the wind. If the wind speed doubles, the concentration of pollutants drops by 50%. If the city is enveloped in an inversion and the air is stagnant, or if the town is sheltered in a valley, exhaust fumes will simply swill backwards and forwards with the motion of the traffic.

Because of their organic development and chaotic structure, urban areas of the UK are often difficult for Mother Nature to sweep clean. In America, where the cities are much younger and planned on a checkerboard system, the wind can rattle through without hitting a brick wall. The reason Los Angeles infamous lurks under a pall of pollution is because off-shore breezes are deflected back by the stone wall of the San Gabriel Mountains. Air layers of different temperatures hold down the pollution, preventing its escape to the east.

Of course all the wind does is shift the problem around. Carbon monoxide, for example, does not appear to be accumulating in the atmosphere, though there is an ominous uncertainty surrounding its disappearing act. Sulphur and nitrogen dioxides we know more about, but not as much as the Scandinavians. They take delivery of our windswept waste in the form of acid rain.

But the weather is just as likely to conspire against dispersal. On a hot summer day, oxides of nitrogen and hydrocarbons react together photochemically under the influence of sunlight and temperature to create ground level ozone. This is what bubbles away over LA and hit London so badly in the summer of '96.

Ozone is a secondary pollutant and the irritant that makes eyes stream, throats rasp and increases an individual's sensitivity to allergens like pollen. It is bad news for anybody with a respiratory problem, and as often as not affects those living down wind of our cities, in rural areas, more dramatically.

Then there is precipitation. The reason the city smells so fresh after a cloud burst is because the rain has indeed flushed the pollutants from the atmosphere. Unfortunately it has dumped them in our gardens, gutters, streams and fields. As research around Spaghetti Junction demonstrated back in the 1970s, it is then a short journey for heavy metals to travel from soil to carrot to stomach.

It's a bleak picture, made worse by the knowledge that there are roughly 25 million cars in the UK, expected to rise to 50 million by 2025, each pumping out an average 1/4 tonnes of pollution a year.

The only good news the Environment Agency has for us is that nitrogen oxides and their contribution to soil acidification will decrease over the coming years. This is largely due to the phasing out of old bangers and the fact that all cars since 1992 are fitted with catalytic converters.

Short of sneaking up behind a belcher and jamming a spud up its exhaust pipe, there is naff all city commuters can do about the nightmare we are expected to cycle through. We are at the mercy of governments that are terrified of tackling the problem at source, a road lobby that lurks over them like Mephistopheles, and motorist who are too selfish and lazy to take the initiative themselves.

But all is not doom and gloom. Of all those passive chokers sucking up air-borne poisons, cyclists are the least affected and best equipped to the counter their impact.


© John Stuart Clark


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