The expansion of the controversial ultra low emission zone (ULEZ) has now come into force in London’s outer boroughs

• I WRITE on the eve of the start of the ULEZ, ultra low emission zone, expansion, which has been “explained” in the press as designed to focus on reduction of air pollution in and around the city.

One component of pollution is the presence of tiny particles, on which the World Health Organisation has set a tough target (not often mentioned in the press) for air to reach, in terms of absence of such particles.

Some research has found microparticles in people who have, and who have died with, lung diseases. I may have such particles aboard, myself, though I am lucky not to have suffered yet.

Those who have internet access can get basic information on the amounts of microparticles reported in the air. Enter PM2.5 levels (in London, or whichever other city one wants to study – let’s say one is travelling to, or has relatives in, another city) and here are a few values reported this morning: New Delhi 183, Canberra 168, Rome 99, Tokyo 70, Dhaka 61, Abuja 58, Berlin 11, Beijing 9, London 4, Paris 2.5.

Further figures show that such values vary greatly across the day and also over the seasons. So one might consider it wiser to study averages across the year.

In looking at these figures it does also seem that there may be, or are, problems of accuracy (might travellers to Nigeria be convinced that Lagos, with a score this morning of 6, be so much clearer than Abuja?) See its level reported above.

Overall it appears that London has much lower levels of this particular pollutant than have other great cities.

Further it is very difficult to discover what the “carbon footprint” or degree of release of microparticles is from the so-called “scrappage” of older vehicles. There is an element of mystery about this, suggesting that the offending objects simply disappear.

Since it is reported that much of the tiny particles arise from wear on vehicle brakes and tyres, and this will continue to occur from service and transport vehicles, we may find that the whole ULEZ scheme may impose a significant cost on the economy of the city and those who live in and serve it, while London is hardly in the front line of cities on this clamour of the WHO’s alarm bells.

MALLORY WOBER, NW3