Thin film of red dust enveloping parts of country for two weeks in 2014 came mostly from farms in mainland Europe and local emissions, study says
Britain’s most serious air pollution event in the past 10 years was only partly caused by “natural” dust blowing in from the Sahara desert and mostly came from farmers fertilising their fields and industrial emissions from mainland Europe, a scientific paper has concluded.
The event, which lasted nearly two weeks in March and April in 2014, raised pollution levels to the highest level across much of Britain and France and for a short while spread a thin film of red dust across some parts of south-east England.
Although Defra and the Met office had warned people to stay indoors as air pollution worsened, it was the Sahara dust which caught the public and media imagination and led to No 10 dismissing the air pollution as natural and suggesting it was beyond the control of government or industry.
Cameron did not go on his usual morning run because of the pollution and on 3 April, nearly a week after levels soared, he told BBC1’s Breakfast TV: “It is unpleasant, and you can feel it in the air. But it’s a naturally occurring weather phenomenon. It sounds extraordinary, Saharan dust, but that is what it is.”
The authors of the study say that chemical analysis of the minute particles of pollution in the air showed that the desert dust was only present for a short time near the end of the 10-day pollution episode.
“The spring 2014 PM [particulate matter] episode was widely perceived as being associated with an enhanced surface concentration of mineral dust from the Sahara. An implication is that this was, at least in part, a ‘natural’ event,” they said in the scientific journal Environmental Research Letters.
“A significant contribution of Saharan dust at surface level was restricted only to the latter part of the elevated PM period and to a relatively small geographic area in the southern part of the UK.”
They showed through modelling that the dust was present at substantial surface concentrations only in the southern UK. “Overall, the percentage of modelled Saharan dust in PM2.5 and PM10 is less than 20% for most of the UK,” said the paper.
The authors say that much of the pollution came from European farmers spreading ammonia-based fertiliser on their fields mixing with local pollution, from industry and traffic. Ammonia is a gas emitted from fertilisers and manure which condenses to form particles which can be blown long distances by the wind.
“The elevated PM during this period was mainly driven by ammonium nitrate, much of which was derived from emissions outside the UK. In the early part of the episode, Saharan dust remained aloft above the UK.”
The result, says the paper, was that the public was misinformed about air pollution. “The pollution episode in spring 2014 was widely attributed to Saharan dust in the UK media, thus placing a (false) emphasis on a natural phenomenon, which cannot be addressed by policy action.”
The authors added: “The focus on an ‘exciting headline’ may be attributable to the complexity of communicating atmospheric processes and the public observations of dust-fall on surfaces. There is a danger that important messages to high-level policy-makers may be obscured by attention-catching headlines.”
“The initial mischaracterisation of the PM event may also represent a missed opportunity to inform and educate the general public about the role of anthropogenic emissions, specifically agricultural emissions of ammonia, as a key contributor to many high PM pollution events in recent years,” they said.
Alan Andrews, a lawyer at the environment law firm ClientEarth which is mounting a legal challenge against the government’s air pollution cleanup plan, said: “This proves what many of us suspected at the time – politicians blamed the smog on Saharan dust when it was really caused by man-made pollution.
“By dismissing this as a natural phenomenon, the government was able to dodge taking any action. This is a betrayal of the thousands of people who are dying early each year in the UK from being forced to breathe dangerous levels of pollution.
“Instead of lobbying in Brussels for weaker pollution targets, our government should be working with our European neighbours to cut pollution across the continent and acting to reduce the home-grown pollution which chokes our towns and cities on a daily basis.”
The study comes as the UK government pushes to water-down new EU targets for ammonia emissions, having recently succeeded in halving its own proposed reduction target for 2030 from 24% to 11%.