When T.S. Eliot wrote about smog it was so dense that it was frequently impossible to see the kerb from the driver’s seat. On one occasion the climatic conditions trapped the smog in a layer above London and although the fog wasn’t evident at street level, at lunchtime pitch darkness suddenly fell.

As the sunlight was blocked out the waiters switched on the lights in the restaurant where I was eating and drivers on the streets outside needed to turn on the headlights. Amazingly, everyone behaved as if this was an everyday occurrence.

In hospitals at this time, whenever there was a “peasouper”, patients with asthma, chronic bronchitis and emphysema flooded into the accident and emergency department. These were one of the few occasions when it was accepted by surgeons that they would have to give up their acute beds to their colleagues, the physicians. The death rate during these foggy or smoggy days or weeks was always appalling.

Neither T. S. Eliot nor the average citizen would now recognise the atmosphere in London or any other great cities. Now smog, when it comes on hot muggy days with temperatures in the Eighties and humidity at New Orleans levels, leaves most of us sweating but breathing comfortably. There are exceptions. Those with COPD (the current name for chronic bronchitis and emphysema), asthma and the elderly whose breathing is impaired, are in danger.

Last week the warning of potentially dangerous high pollution levels and smog coincided with disturbing news for some patients with asthma. One of the standbys of asthma treatment, the long-acting beta 2 agonists, however successful at reducing the overall number of attacks of asthma, are associated with an increase in the number of severe attacks of asthma (occasionally with a fatal outcome) when taken regularly and as the only form of treatment. Long-acting beta agonists relax the smooth muscles of the patient’s airways, so that they can breathe more readily. They may be safely used with other medication as part of the treatment to reduce the number of attacks of asthma and possibly to prevent them altogether.

Regular readers of this column will have known for years that the sole use of long-acting beta agonist drugs that rely for some of their effect on such preparations as salmeterol and formoterol, the long-acting beta agonists that are commonly prescribed for asthmatic patients, should never be used alone.

A study published last week considered the treatment of more than 33,000 patients. It showed those patients who need regular daily treatment should always use the long-acting beta agonists with another substance — presumably a steroid. I always prescribe Symbicort, a steroid, Pulmicort budesonide, combined with a long-acting beta agonist, formoterol. This is only a personal preference. There are undoubtedly other equally effective combinations.

The British Thoracic Society guidelines suggest that “long-acting beta agonists on their own are not safe and this monotherapy is neither supported by current evidence, nor encouraged by the British Thoracic Society”. Similarly the American Food and Drug Administration warned a year ago that salmeterol, possibly the most commonly prescribed beta agonist, was associated with rare instances of serious asthma episodes or asthma-related deaths.

Many cases in which asthma attacks are occasional may be adequately controlled by the use of a short-acting selective beta 2 agonist that should provide relief for three to six hours. They are used as required but not regularly. Once they are having to be used too often it is an indication that the patient’s treatment needs review, and they are going to require long-term care that will include changing to the regular use of an inhaled steroid plus a long acting beta agonist — but NEVER a long-acting beta agonist inhaler by itself.

There are approximately five million people who suffer from asthma. An increasing number are now taking a closer interest in their own treatment, and an increased responsibility in the management of their long-term condition. This has proved successful, especially when they have self-management plans. It is important that these should now always include the advice that long-acting beta agonists used by themselves are not recommended.

The general rules when advising patients are that everyone with asthma should understand what to do in an emergency; which inhaler provides immediate treatment for short-term relief and which is used regularly to reduce the number of asthma attacks or preferably to keep them at bay altogether (and what both look like); how often the long-term treatment inhaler should be used and at what dose; and how to recognise any deterioration in their symptoms that needs medical advice. Above all, they need to practise the use of their inhaler under supervision so that they receive the intended dose.

Although urban pollution is more likely to induce an asthma attack, paradoxically it doesn’t cause more people to develop asthma in the first place as does country life. This is especially true if country life is lived during early childhood in hyper clean, spotless, crumb- and mud-free conditions, without much contact with animals or other people. The yellow fog that rubs its back upon the window-panes.