A document introducing the topic of photochemical smog. very useful for the geography topic of climatic hazards.

1. MatthewMortimer
Photochemical Smog
Photochemical smogisamixture of smoke andfog.Photochemical smogformswhenphotonsof
sunlighthitmoleculesof differentpollutantsandcause chemical reactions.The pollutantsinclude
nitrogenoxides,volatileorganiccompounds andozone.
Airpollutionisassociatedwithhighpressure.Thisisbecause windsinahighpressure systemare
oftenweak,meaningpollutantsare notdispersed.Underanticyclone conditions,poorairqualitycan
persistformanydays.One factor that often leadstophotochemical smogishumanactivity,suchas
the emissionof pollutants.Roadtransportaccountsfor 44% of VOCs,55% of NOx and 87% of carbon
monoxide emissions.The effectof the pollutionisstingingeyes,coughing,headachesandchest
pains. Ozone canharm lungtissues,impairthe body’sdefence mechanism, increase respiratorytract
infections,andaggravate asthma,bronchitisandpneumonia.The longtermeffectsare premature
agingof the lung,as seeninchildreninLosAngeles.Incitycentresitisnitrogendioxideratherthan
ozone thatis likelytobe the mainpollutant.Reactionswithoxygenandozone cause car emissionsto
be turnedto nitrogendioxide.Thisdoescause healthproblemsforasthmaandbronchitissufferers;
howeveritdoesrapidlyremoveozone fromcitycentres.Inthe winter,urbanareassurroundedby
highgroundare more at risk.This isbecause the coldair sinksinfromthe surroundinghills,
reinforcingthe temperature inversion.
The effectsof photochemical smogcan be veryserious.InLosAngeles,USA,childrencanhave a 10-
15% reductioninlungcapacityandthere are 1600 premature deathsrelatedtochronicrespiratory
disorderseveryyear.The particlesthatcause these issuesare oftenlessthantenmicronsin
diameterwhichcanflowstraightintothe lung.The numberof asthmasufferersisgrowing
worldwide;inthe UK 1 in 7 childrensufferfromasthma.Inthe USA the costs relatedtoair pollution
are around$40 billionayear.
There are over9 millionvehiclesinLA,meaning
theyare one of the main contributorsto
photochemical smog.
As seenhere inBeijing,heavy industrycreates
lotsof pollutionwhichcreatesthe
photochemical smogshown.