Market failure occurs when the free market results in external costs not accounted for by the producer or the consumer; in this case, smoking.
Smoking in playgrounds could promote the wrong idea about smoking to children. There will be no obvious signs of ill effects as these may take a long time to develop and therefore children may grow up thinking smoking will not cause harm.
A smoking ban in playgrounds is an example of local government intervention which could help reduce the externality and the quantity of consumption. If consumption falls then social costs (which include external costs) will also fall.
BUT this intervention may not work if smokers simply ignore the ban and it is not regulated. so someone smokes and nothing happens to them in the form of punishment and so there is no deterrent.
Even if the ban is enforced this will be expensive.
So, when considering whether it is the 'most effective' then of course you also have to consider other methods such as taxation or information campaigns.
There is also the point that even if you don't smoke in the playground you may smoke in many other places so your total smoking may not fall and the NHS costs also may not fall.
You also consider whether many people smoke in playgrounds at all - if not many then the ban - even if it works - is hardly going to be effective. To be effective it would have to be extended to more areas where children are present.
Ideally the ban is likely to be more effective when used in conjunction with other interventions such as the change in cigarette packaging.
Of course, as readers of this blog know, a smoking ban for playground smokers was considered here....weeks ago
