wanderlust.co.uk September 2019 137HEALTH DISCOVER
Travel
Clinic
Understandingtherisksyoufacewhentravellingthroughpollutedcountriesisonlypartofthe
problem,saysDrJaneWilson-Howarth–thetrickybitisknowingwhatyoucandoaboutthem...with D Jane
Alamy; Dreamstime
Dr Jane Wilson-Howarth lives in
Nepal; you can read her blog at
http://www.wilson-howarth.comM
any major cities have
poor air quality; the worst
are mostly in Asia but the
problem is global (see, for example,
airvisual.com/air-quality-app). The
chemical composition of pollutants,
caused by motor exhausts and
industry, is complex, and ‘particulate
matter’ (PM) can be used as a proxy
for all kinds of urban air pollution.
Air quality counts assess particulate
matter that is less than 2.5 microns in
diameter (PM2.5) and also particulate
matter that is less than 10 microns
across (PM10) – a human hair is
about 50 microns in diameter. The
larger particles lodge in the lungs
while PM2.5 are small enough to
enter the circulation when inhaled
and are even more harmful to health.
These particles are invisible,
tasteless and odourless. The WHO
suggest PM2.5 daily counts should be
below 25μg/m^3 , whereas some city air
is well above that. In pre-monsoon
Kathmandu in 2019, for example,
values of 160μg/m^3 were recorded.In plain sight
In addition to invisible pollutants,
carbon and dust particles reduce
visibility, while ozone and sulphur
dioxide gases sting the eyes and cause
sore throats and drippy noses. This
is unpleasant, but people at normal
levels of fi tness should largely be
unaff ected by this in the short term.
Toxins in the air can also include
nitrous oxides (NOx) and volatile
organic compounds (VOC) including
CFCs (chlorofl uorocarbons), carbonwho are asthmatic, had childhood
asthma or tend to allergic conditions
may become wheezy again. Pollution
increases the risk of chest infections,
even in those not usually susceptible,
and there is also strong evidence that
it signifi cantly reduces life expectancy
and increases the risk of heart disease
and strokes in the long term. Indeed,
it has been said that living in Delhi
is as harmful as smoking two packs
of cigarettes a day. Furthermore,
smokers living in similarly polluted
environments are at even higher risk.Breathing easier
People who choose to workout a lot
in polluted urban environments
should check pollution indices before
doing so. Many people wear masks
but ordinary surgical masks are
completely ineff ective; those
designed for cyclists may give some
protection, but not all perform to
the manufacturer’s claims, however,
and price is no indicator of quality.
In the UK, look out for masks that
have passed the BS EN 149:2001
British Standards test for airborne
particles. Only masks certifi ed to an
occupational hazard level are good
enough for experts in the USA; these
will have a NIOSH rating and should
be fi tted individually and tested to
ensure that they are the correct size.
Many masks on the market do not
reach this NIOSH standard, but it
is helpful to know if they perform
to N95 or N99 levels, which means
they should exclude 95% or 99%
of pollutants respectively.monoxide (CO) and cancer-causing
benzene. There is more on these on
the WHO site (tinyurl.com/WL-aq1).Taking the air
The Air Quality Index (AQI) has been
developed in the USA to give a daily
score for levels of particulates and
ozone that might have an infl uence
on day-to-day symptoms (rather than
long-term health). It is a useful guide
that operates on an simple scale: air
pollution poses little or no risk when
the AQI is below 50, while less than
100 is ‘satisfactory’ (see airnow.gov).
When pollution levels are high
(AQI > 100; PM2.5 > 25 μg/m^3 ), thoseSmog gets in your eyes
(top) Pollution levels in
New Delhi are some of the
worst on the planet, and it
is worth checking AQI
levels if you’re going to be
out for a long time; (below)
not all pollution masks are
created equal, so check
yours meets the correct
independent standards