Understanding toxicity is the key to dealing with pollution

Understanding toxicity is the key to dealing with pollution

by Martin Livermore
article from Monday 16, October, 2017

AS MOST READERS of my regular columns will already be very well aware, toxicity is a relative term. But for the general public, this simple but important concept is all too often misunderstood. For many people, if something is toxic, then it’s dangerous, end of message. To complicate this, many of us are easily capable of a rather bizarre form of Orwellian double-think: we may strive to avoid all traces of synthetic pesticides, for example, while being perfectly willing to consume a wide range of natural chemicals that are demonstrably carcinogenic. In both cases, the dose makes the poison, but one is ‘good’ and one is ‘bad’.

This black or white, good or bad view of things can lead to poor decisions and unwanted outcomes. On one hand, wanting to eliminate pesticide residues on produce has led to more efficient means of crop protection, minimising spraying or extending the interval between spraying and harvesting, for example. On the other hand, highly effective compounds which are toxic in smallish doses but can be used perfectly safely with simple precautions have been phased out because of the hazard they present if these precautions are not taken. Their (lower toxicity) replacements may be less effective, so increasing losses and food costs.

Similarly, it is a failure to take account of the evidence that low doses of radiation cause no ill-effects (and may even have a positive effect on living things, a phenomenon known as hormesis) that has inflated the costs of building new nuclear power stations considerably. Once a safety standard has been set, it’s a very brave legislator who relaxes it, whatever the evidence in favour of doing so.

And yet a new fleet of fail-safe nuclear generating stations is just what is needed at present. They would provide an ideal way of slashing carbon dioxide emissions while providing a reliable, secure supply of electricity; a least-regrets option whether or not climate change turns out to be as significant as projected.

In an opinion piece this week, the inimitable Matt Ridley argued that Politics is obsessed with virtue signalling.  In essence, the means becomes much more important than the result. Adam Smith pointed out long ago that free markets and competition create wealth, despite the fact that they are driven by that most selfish of purposes, the profit motive. But the profit motive is decried despite its key role in creating wealthy societies, and socialism is regarded as ‘good’ despite the clear lessons from every country that has taken that road in all but its mildest form.

Transport has been a battleground for different interpretations of what is ‘good’. Diesel engines were favoured via the tax system when carbon dioxide emissions were the primary focus. However, the diesel engine recently became ‘bad’ because of the higher level of particulates and nitrogen oxides produced by these engines compared with their petrol equivalents.

This has been exacerbated by the ‘Dieselgate’ scandal in which VW (and others?) deliberately used software that improved the official test results for some engines, while allowing much higher levels of emissions under real use conditions. Even without this, the nature of official emissions tests means that in many cases the results are falsely reassuring when compared to the reality of everyday driving.

A combination of pollution charges for entering some urban areas and scrappage schemes offered by many manufacturers have been designed to take older diesels off the road. However, another result has been to discourage sales of new diesels, despite there being little to choose in terms of overall emissions between petrol and diesel variants under the latest Euro 6 standard.

All of this is, in the longer term, overshadowed by the intention of manufacturers to move solely to hybrid and all-electric cars, although there is little sign that all conventional vehicles are likely to disappear over the next twenty or so years without considerable public subsidy. Battery technology may continue to improve, but the increasing demand for lithium and other essential elements is also driving up prices of these commodities.

In the meantime, this demonization of diesel may turn out to be something of a blind alley. The justification at present is the need to reduce urban air pollution to meet the latest standards and reduce negative impacts on health. This would be helped enormously by using hybrid cars in electric-drive mode in built-up areas, but on the open road diesel or petrol still makes more sense overall.

Diesels are, of course, still emitting similar amounts of PM2.5 and NOx into the air wherever they are driven, but out of town these emissions are diluted in a much greater volume of air. Since it is the concentration – the dose – that is important, any health impact is minimised. It is the geography of urban streets that contains emissions and creates the problem.

Campaigners are pushing for similar reductions in emissions from shipping. Ships use very low-grade fuels, as we can readily see from what comes out the funnel. This may not be very aesthetic, but the exhaust is rapidly diluted in the open air over the sea. Since even busy sea lanes are very uncrowded places compared to cities or even rural roads, this obvious pollution causes no practical problem, while making good use of heavy oil fractions which would otherwise be effectively wasted.

This is not an argument for simply ignoring air quality. This has certainly improved enormously over the last 50 years, but could still be better. However, it would be better to look at the end result and prioritise goals rather than take a sledgehammer – banning the internal combustion engine – to crack a nut – urban air quality.

The campaign against the internal combustion engine is couched in terms of air pollution at present, but the main driver behind it is still the ambitious goal of slashing carbon dioxide emissions. Cars are a relatively soft target for politicians to focus on at present, but the real heavy lifting comes with the enormous task of developing a reliable, cost-effective, zero-carbon electricity supply capable of heating homes and offices and powering all road and rail transport as well as displacing conventional generation sources for present uses of electricity. While this is generally seen as a ‘good’ objective, opinion may change quickly if costs are high, energy security is lower and the rest of the world fails to follow suit.

Martin Livermore writes for the Scientific Alliance, which advocates the use of rational scientific knowledge in the development of public policy. To subscribe to his regular newsletter please use this link.

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