More than 45,000 peo­ple are thought to die each year in the UK be­cause of air pol­lu­tion

LEAD­ERS FROM ATHENS, MEX­ICO CITY, PARIS AND MADRID HAVE RECENTLY AN­NOUNCED THAT DIESEL VE­HI­CLES WILL BE BANNED IN THEIR CITIES FROM 2025, DUE TO POL­LU­TION CON­CERNS. SO WHAT EF­FECT DO DIESEL EMIS­SIONS HAVE ON OUR HEALTH, AND SHOULD WE BE WOR­RIED? Words: Pr

Focus-Science and Technology - - News -

Look out­side. Per­haps it’s a bright and cold day, and you’re think­ing of cy­cling into town. But you might want to think again. You may be about to put your­self in harm’s way from high lev­els of com­pounds at the cen­tre of a ma­jor pub­lic health is­sue: air pol­lu­tion.

Air pol­lu­tion has long been re­garded as a threat that van­ished with the smoke-belch­ing fac­to­ries of yes­ter­year. And while the dense ‘pea-souper’ smogs of the 1950s may have gone for good, they have been re­placed by in­vis­i­ble forms of pol­lu­tion that build up on bright, still days – es­pe­cially dur­ing the cooler months of the year. Ex­actly how such pol­lu­tants af­fect our health is the sub­ject of ur­gent re­search, but there’s grow­ing con­cern that they pose a ma­jor health threat. Air pol­lu­tion is back at the top of the UK pub­lic health agenda, im­pli­cated in the deaths of tens of thou­sands of peo­ple each year.

Ac­cord­ing to Prof Dame Sally Davies, chief med­i­cal of­fi­cer for Eng­land, it’s al­ready clear that the el­derly and those with pre- ex­ist­ing heart dis­ease or lung dis­or­ders are

par­tic­u­larly at risk. “How­ever, re­searchers are find­ing that air pol­lu­tion may be as­so­ci­ated with a much wider range of health con­di­tions,” she says. Th­ese in­clude di­a­betes and neu­ro­log­i­cal dis­ease. Un­born ba­bies can even be af­fected.

Davies is one of many lead­ing health ex­perts now call­ing for ac­tion. The Na­tional In­sti­tute for Health and Care Ex­cel­lence (NICE) has recently un­veiled draft pro­pos­als on how to tackle the is­sue, fol­low­ing le­gal ac­tion against the UK gov­ern­ment, which has been found to be in breach of Euro­pean stan­dards for air qual­ity.

HAZY DAYS

The resur­gence of pub­lic con­cern about air pol­lu­tion has been sparked by the scan­dal sur­round­ing diesel cars built by Volk­swa­gen. In 2015, the US En­vi­ron­men­tal Pro­tec­tion Agency (EPA) re­vealed that the Ger­man-based man­u­fac­turer had fit­ted its ve­hi­cles with tech­nol­ogy that sensed when the car was un­der­go­ing an emis­sions test, and al­tered its per­for­mance to en­sure com­pli­ance. But once on the road, the car re­verted to its nor­mal per­for­mance – and far higher emis­sions of ox­ides of ni­tro­gen (NOx), one of the pol­lu­tants now prompt­ing con­cern. Yet the scan­dal came as lit­tle sur­prise to air qual­ity ex­perts. Ac­cord­ing to Prof Alas­tair Lewis of the Univer­sity of York, sci­en­tists had ex­pected NOx lev­els to be de­clin­ing in city cen­tres as old ve­hi­cles were re­placed by new, sup­pos­edly cleaner ones. “But this was based on cars emit­ting NOx at the rates sug­gested by the man­u­fac­tur­ers’ test data,” ex­plains Lewis. Fol­low­ing EPA’s rev­e­la­tions, the rea­son why there had been no de­cline was all too ob­vi­ous.

NOx is not the only, or even most harm­ful, form of pol­lu­tion emit­ted by diesel en­gines. They also spew out so- called par­tic­u­late mat­ter (PM), tiny specks of car­bon laced with or­ganic com­pounds like sul­phates and met­als. Short-term PM ex­po­sure causes acute ir­ri­ta­tion to the eyes, throat, nose and lungs, while peo­ple with con­di­tions like asthma can suf­fer more se­vere symp­toms. But long-term ex­po­sure can pose a broader risk, says res­pi­ra­tory med­i­cal ex­pert Prof An­thony Frew of the Royal Sus­sex County Hos­pi­tal, Brighton: “There’s data sug­gest­ing that diesel par­ti­cles can leave peo­ple more prone to al­ler­gic re­sponses, and pro­mote in­flam­ma­tion of the air­ways.”

Stud­ies sug­gest that PM may pose a par­tic­u­lar risk to the el­derly and those with heart dis­ease. “It can cause car­diac rhythm is­sues – though we don’t know if the ef­fect hap­pens im­me­di­ately on ex­po­sure, or takes some time,” says Frew.

Mys­tery also sur­rounds the long-term ef­fects of ex­po­sure. In a study of the health of over 360,000 peo­ple in Eng­land and Wales, a team led by Dr Anna Hansell of Im­pe­rial Col­lege Lon­don found that ex­po­sure to pol­lu­tion in the 1970s still

af­fected health al­most 40 years later. The team also found that while lev­els of air pol­lu­tion are now far lower than in the 1970s, it seems to be more toxic.

Ex­actly why isn’t clear, and some ex­perts have ques­tioned the find­ing. Even so, there is an emerg­ing con­sen­sus that air pol­lu­tion is a ma­jor health hazard. In a re­port pub­lished just be­fore the VW scan­dal broke, the De­part­ment for En­vi­ron­ment, Food and Ru­ral Af­fairs (De­fra) put the es­ti­mated num­ber of deaths in the UK due to ox­ides of ni­tro­gen and PM at over 45,000 per year.

It’s a shock­ing statis­tic – over 25 times the an­nual num­ber of fa­tal­i­ties on roads. But it has been backed by the Royal Col­lege of Physi­cians and Royal Col­lege of Pae­di­atrics and Child Health. Their joint re­port is­sued last year stressed that the threat from air pol­lu­tion has evolved over re­cent decades. “Ev­ery­one thought that the prob­lem of air pol­lu­tion was over. But how wrong we were,” said Prof Stephen Hol­gate, chair of the group which put to­gether the study. He be­lieves the time has come for “ur­gent, de­ter­mined and mul­ti­dis­ci­plinary ac­tion” to tackle the threat.

CITY SHAKE-UP

Un­sur­pris­ingly, there are al­ready calls for dra­co­nian ac­tion against diesel ve­hi­cles in cities. In Novem­ber, Lon­don’s mayor Sadiq Khan called for a scrap­page scheme and taxes to en­cour­age a switch

Lis­ten to So I Can Breathe, a sea­son ex­plor­ing air pol­lu­tion, 6-12 March.

LEFT: In the 1950s, Lon­don’s chok­ing ‘pea-souper’ smogs were caused by burn­ing coal as fuel. While the city’s air looks clearer to­day, it’s still laden with pol­lu­tants – this time from ve­hi­cle emis­sions

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