It is now
generally accepted that the very small particles emitted into the
surrounding air by combustion
and abrasion have a large effect on annual death rates. In a
typical west European and North American population, a modest
10microgramme /m3 increase in the ambient annual average level of PM2.5
is associated with a 6% increase in death rate. Built up areas
where solid domestic fuel combustion is common can easily raise PM2.5
levels by 20 microgramme per cubic metre. People often ask how
this compares to living close to heavy traffic. The answer is
that although heavy traffic causes particulate levels to increase in a
locality for which there is much evidence, domestic fires typically
emit more particulates. A heavy goods vehicle will emit about 5kg
of PM10 particles per year. A house fire burning two tonne of
fuel at the UK smokeless limit will emit just under 10kg. That
illustrates why domestic fire pollution is important.
Independent newspaper article on home fires
of the American Medical Association, Arden Pope III et al
(last accessed Feb '09)
more . . . . .
Air has tiny solid particles or fine liquid droplets suspended within it often called particulates. Usual concentrations are invisible but high concentrations can be seen as a haze, a mist or smoke especially when accompanied by condensing water vapour. The large majority are less than a hundreth of a millimetre across and are known as P M tens (PM10 = particle ten m icrometres = 10µm). The fraction of the PM10's which are thought to be the most poisonous are less than 2.5 micrometres across and are called PM2.5's. The smallest of the particulates are the ultrafine particles which are smaller than 0.1µm across (PM0.1) and often contain less than a million molecules. There are many millions of PM10's suspended in each cubic metre of even clean air. The chemistry of suspended particulate matter is varied and depends upon the source and can contain carbon, nitrates, sulphates, metals, polycyclic aromatic hydrocarbons to name but a few. When coal or wood is burnt, many of the poisonous emissions start as vapour but quickly condense onto surfaces such as the inside surface of chimney stacks or onto the surfaces of the suspended particles. Particles are the main delivery system for many of the inhalable poisons.
Natural as fine dust,
spray etc.. Anthropogenic (man made) primary
particles direct from combustion mainly but other sources include
Also secondary particles formed in the air due to chemical reaction.
PM10's are readily inhalable and because of their small size are not filtered and penetrate deeply into the cardiovascular system where they cause damage. Those smaller than 2.5 um penetrate deeper than those closer to 10um. Mainly because of their physical properties, they have a strong association with most types of respiratory illness and even mortality. They also have a strong association with circulatory (heart disease and strokes) disease and mortality. Particles allow many chemicals harmful to human health to be carried to many of our internal organs causing a wide range of illness and mortality including cancer, especially lung cancer, brain damage and damage to the unborn child.
A list of health effects
compiled by the US EPA who state that elevated particulate
concentrations have been associated with:
Size of Health Effects
Long term exposure has been estimated by the UK
government to reduce life expectancy by 3.5 days per microgram/m3
averaged over a whole population. Therefore, if four percent of the
population are made ill and killed by a lifetime particle exposure of
PM10's and if exposure averages 30µgm-3 then the loss in life years per
affected person would be more than ten. The annual number of deaths
would be 24 000. Within this group, there would be a minority with
a larger loss
in life years. People living in close proximity to a coal or wood fire
would have a higher long term exposure, in some cases much higher.
* probably an over estimate: 1.08 and 1.24
are probably better figures.
Short term exposure causes death advancement and hospital admissions mainly but perhaps not exclusively in those frail, very elderly or seriously ill. The UK government have estimated the numbers affected as:
Again, the doses are ambient levels. The response, in many cases could be from those exposed to higher levels and close to those sources driving the ambient levels.
General annual averages for UK
are between 15 and 35 ug/m3 but less
for many rural areas. Actual exposures vary and for many people are
above ambient levels. Living in the general vicinity of industrial
sites, including quarries and combustion power stations will expose you
to higher particle pollution. Also living near roads and in areas of
domestic combustion activity will expose you to higher than ambient
levels. Environmental tobacco smoke can expose you anywhere between 17
and 5000ug/m3 PM2.5's. Being near to roads often means a concentration
of up to 15 µg m -3 of PM10's above the local
background. In Christchurch, New
Zealand, domestic wood heating is common and summer PM10's level are
less than 20ug/m3 whilst winter ambient levels often rise above
Indoor air where a domestic fire is burning can make concentrations
1000ug/m3. Biomass smoke from cooking appliances in the developing
often means women and children being exposed to over 5000ug/m3 for
hours per day and the consequent death rate is high, over 2 million a