SHORTLY before, and for several weeks after supermarkets and shops began charging for plastic carrier bags, I was contacted by a radio chat show to add my tuppence worth to a discussion.

For some reason it was presumed I would be against this initiative, which was baffling and vaguely insulting. Needless to say, I declined to take part.

How could anyone think it bad to cut down on the plastic clogging our gutters, choking our seas, not to mention flapping like tattered pirate flags from every windblown tree?

In the years since 2014 there has been a marked difference in the river where until recently I lived – a wide and fast-flowing stretch of water which, if you could walk on the backs of swans and ducks and moorhens, you could cross without getting wet.

As a result, the biggest threat these creatures face is from overzealous bird-lovers fattening them on white bread.

Now, with Tesco announcing it is no longer to sell the flimsy one-use 5p bags (except for home deliveries) and offer only 10p bags for life, environmentalists and wildlife can breathe even easier.

Tesco’s motives are not, one suspects, wholly driven by green principles. The cost-saving will be huge, while the amount of extra plastic used to produce heavier bags is considerable.

But it is probable that, in the longer term, as people’s habits change further, it is a step in the right direction, and one other companies look likely to follow.

It’s remarkable how promptly we adapt to new ways of behaving, especially when it saves us money. Within months of the 5p charge, the use of bags plummeted.

Earlier, when Holyrood first introduced the smoking ban in enclosed public places, there were moans and groans and there was much bellyaching.

Today? Only a woolly mammoth would not agree it has been a major factor in improving the way we live, protecting the health of millions of passive inhalers as well as encouraging smokers to give up.

Introducing both these measures took courage, for which various governments deserve great credit.

If (one fervently hopes when) Holyrood also carries through its oft-thwarted intention to introduce minimum pricing for alcohol, it will have cleared another significant hurdle in the way of benefitting public health.

Thus far, thus commendable. So why is it that, faced with escalating pollution and illegal levels of air quality in many built-up areas, there seems no appetite, no backbone, to make another equally tough but equally necessary decision?

Fumes from traffic represent a deadly and indiscriminate threat about which no individual can do much beyond wear a mask.

It is estimated that around 2,500 people a year in Scotland die early as a result of poor air quality, a problem that blights not just Edinburgh, Glasgow and the largest cities, but also14 of our councils. In its proposals for the future, air quality certainly features, but Holyrood gives the impression of being committed to addressing this issue with kid gloves, when what is needed is a sledgehammer.

As well as advocating enhanced public transport there has been talk of low-emission zones.

Such ventures are part of a long-term solution, as are educational efforts to help punters make better informed decisions.

But in the time it takes for the message about walking and cycling and catching the bus gradually to percolate and alter the way we behave, much foul air will have been breathed.

Surely it makes sense that, while that important grass-roots reprogramming gets underway, there should also be a more radical, less consumer-friendly strategy that needs to be implemented fast.

A congestion charge has been mooted for Glasgow, although little has been said on that lately. Has the Government got cold feet? As one who can taste the petrol in the evening air in George Square, I would urge immediate action; and not just in the two main cities, but right across the land.

Getting behind the wheel is almost as much an addiction as lighting a fag or reaching for a drink. The hypnotic pull of the car has to be addressed, be it in the Merchant City or the Mearns.

Nothing less than a countrywide shift in outlook, a dramatic rethinking of our relationship with the road, is required to address the problem.

The 5p bag shows that, when you hit people’s pockets, they are quick to respond.

Phasing out diesel and petrol cars is a slow-burn response and takes no account of the pollution even the greenest cars produce.

To get ahead of this predicament, we need drastically to cut not only emissions but also the number of cars themselves.

As it has done in the past, Holyrood must take a brave stand, or be accused of a shameful lack of will.

Introducing congestion charges and clearing the air could make the biggest health and environmental difference yet seen this century; and that’s saying something.