Atmospheric particulate matter | Wikipedia audio article

Atmospheric particulate matter | Wikipedia audio article


Particulates – also known as atmospheric
aerosol particles, atmospheric particulate matter, particulate matter (PM), or suspended
particulate matter (SPM) – are microscopic solid or liquid matter suspended in the atmosphere
of Earth. The term aerosol commonly refers to the particulate/air mixture, as opposed
to the particulate matter alone. Sources of particulate matter can be natural or anthropogenic.
They have impacts on climate and precipitation that adversely affect human health, in addition
to direct inhalation. Subtypes of atmospheric particles include
suspended particulate matter (SPM), thoracic and respirable particles, inhalable coarse
particles, which are coarse particles with a diameter between 2.5 and 10 micrometers
(μm) (PM10), fine particles with a diameter of 2.5 μm or less (PM2.5), ultrafine particles,
and soot. The IARC and WHO designate airborne particulates
a Group 1 carcinogen. Particulates are the most harmful form of air pollution due to
their ability to penetrate deep into the lungs and blood streams unfiltered, causing permanent
DNA mutations, heart attacks, respiratory disease, and premature death. In 2013, a study
involving 312,944 people in nine European countries revealed that there was no safe
level of particulates and that for every increase of 10 μg/m3 in PM10, the lung cancer rate
rose 22%. The smaller PM2.5 were particularly deadly, with a 36% increase in lung cancer
per 10 μg/m3 as it can penetrate deeper into the lungs. Worldwide exposure to PM2.5 contributed
to 4.1 million deaths from heart disease and stroke, lung cancer, chronic lung disease,
and respiratory infections in 2016. Overall, ambient particulate matter ranks as the sixth
leading risk factor for premature death globally.==Sources of atmospheric particulate matter
==Some particulates occur naturally, originating
from volcanoes, dust storms, forest and grassland fires, living vegetation and sea spray. Human
activities, such as the burning of fossil fuels in vehicles, stubble burning, power
plants, road dust, wet cooling towers in cooling systems and various industrial processes,
also generate significant amounts of particulates. Coal combustion in developing countries is
the primary method for heating homes and supplying energy. Because salt spray over the oceans
is the overwhelmingly most common form of particulate in the atmosphere, anthropogenic
aerosols—those made by human activities—currently account for about 10 percent of the total
mass of aerosols in our atmosphere.==Composition==The composition of aerosols and particles
depends on their source. Wind-blown mineral dust tends to be made of
mineral oxides and other material blown from the Earth’s crust; this particulate is light-absorbing.
Sea salt is considered the second-largest contributor in the global aerosol budget,
and consists mainly of sodium chloride originated from sea spray; other constituents of atmospheric
sea salt reflect the composition of sea water, and thus include magnesium, sulfate, calcium,
potassium, etc. In addition, sea spray aerosols may contain organic compounds, which influence
their chemistry. The drift/mist emissions from the wet cooling towers is also source
of particulate matter as they are widely used in industry and other sectors for dissipating
heat in cooling systems.Secondary particles derive from the oxidation of primary gases
such as sulfur and nitrogen oxides into sulfuric acid (liquid) and nitric acid (gaseous). The
precursors for these aerosols—i.e. the gases from which they originate—may have an anthropogenic
origin (from fossil fuel or coal combustion) and a natural biogenic origin. In the presence
of ammonia, secondary aerosols often take the form of ammonium salts; i.e. ammonium
sulfate and ammonium nitrate (both can be dry or in aqueous solution); in the absence
of ammonia, secondary compounds take an acidic form as sulfuric acid (liquid aerosol droplets)
and nitric acid (atmospheric gas), all of which may contribute to the health effects
of particulates.Secondary sulfate and nitrate aerosols are strong light-scatterers. This
is mainly because the presence of sulfate and nitrate causes the aerosols to increase
to a size that scatters light effectively. Organic matter (OM) can be either primary
or secondary, the latter part deriving from the oxidation of volatile organic compound]s
(VOCs); organic material in the atmosphere may either be biogenic or anthropogenic. Organic
matter influences the atmospheric radiation field by both scattering and absorption. Another
important aerosol type is elemental carbon (EC, also known as black carbon, BC): this
aerosol type includes strongly light-absorbing material and is thought to yield large positive
radiative forcing. Organic matter and elemental carbon together constitute the carbonaceous
fraction of aerosols. Secondary organic aerosols (SOAs), tiny “tar balls” resulting from combustion
products of internal combustion engines, have been identified as a danger to health.The
chemical composition of the aerosol directly affects how it interacts with solar radiation.
The chemical constituents within the aerosol change the overall refractive index. The refractive
index will determine how much light is scattered and absorbed.
The composition of particulate matter that generally causes visual effects such as smog
consists of sulfur dioxide, nitrogen oxides, carbon monoxide, mineral dust, organic matter,
and elemental carbon also known as black carbon or soot. The particles are hygroscopic due
to the presence of sulfur, and SO2 is converted to sulfate when high humidity and low temperatures
are present. This causes the reduced visibility and yellow color.==Size distribution of particulates==Aerosol particles of natural origin (such
as windblown dust) tend to have a larger radius than human-produced aerosols such as particle
pollution. The false-color maps in the third image on this page show where there are natural
aerosols, human pollution, or a mixture of both, monthly.
Among the most obvious patterns that the size distribution time series shows is that in
the planet’s most southerly latitudes, nearly all the aerosols are large, but in the high
northern latitudes, smaller aerosols are very abundant. Most of the Southern Hemisphere
is covered by ocean, where the largest source of aerosols is natural sea salt from dried
sea spray. Because the land is concentrated in the Northern Hemisphere, the amount of
small aerosols from fires and human activities is greater there than in the Southern Hemisphere.
Over land, patches of large-radius aerosols appear over deserts and arid regions, most
prominently, the Sahara Desert in North Africa and the Arabian Peninsula, where dust storms
are common. Places where human-triggered or natural fire activity is common (land-clearing
fires in the Amazon from August–October, for example, or lightning-triggered fires
in the forests of northern Canada in Northern Hemisphere summer) are dominated by smaller
aerosols. Human-produced (fossil fuel) pollution is largely responsible for the areas of small
aerosols over developed areas such as the eastern United States and Europe, especially
in their summer.Satellite measurements of aerosols, called aerosol optical thickness,
are based on the fact that the particles change the way the atmosphere reflects and absorbs
visible and infrared light. As shown in the seventh image on this page, an optical thickness
of less than 0.1 (palest yellow) indicates a crystal clear sky with maximum visibility,
whereas a value of 1 (reddish brown) indicates very hazy conditions.==Deposition processes==In general, the smaller and lighter a particle
is, the longer it will stay in the air. Larger particles (greater than 10 micrometers in
diameter) tend to settle to the ground by gravity in a matter of hours whereas the smallest
particles (less than 1 micrometer) can stay in the atmosphere for weeks and are mostly
removed by precipitation. Diesel particulate matter is highest near the source of emission.
Any info regarding DPM and the atmosphere, flora, height, and distance from major sources
would be useful to determine health effects.==Controlling technologies==
A complicated blend of solid and liquid particles result in particulate matter and these particulate
matter emissions are highly regulated in most industrialized countries. Due to environmental
concerns, most industries are required to operate some kind of dust collection system
to control particulate emissions. These systems include inertial collectors (cyclonic separators),
fabric filter collectors (baghouses), wet scrubbers, and electrostatic precipitators.
Cyclonic separators are useful for removing large, coarse particles and are often employed
as a first step or “pre-cleaner” to other more efficient collectors. Well-designed cyclonic
separators can be very efficient in removing even fine particulates, and may be operated
continuously without requiring frequent shutdowns for maintenance.Fabric filters or baghouses
are the most commonly employed in general industry. They work by forcing dust laden
air through a bag shaped fabric filter leaving the particulate to collect on the outer surface
of the bag and allowing the now clean air to pass through to either be exhausted into
the atmosphere or in some cases recirculated into the facility. Common fabrics include
polyester and fiberglass and common fabric coatings include PTFE (commonly known as Teflon).
The excess dust buildup is then cleaned from the bags and removed from the collector.
Wet scrubbers pass the dirty air through a scrubbing solution (usually a mixture of water
and other compounds) allowing the particulate to attach to the liquid molecules. Electrostatic
precipitators electrically charge the dirty air as it passes through. The now charged
air then passes through large electrostatic plates which attract the charged particle
in the airstream collecting them and leaving the now clean air to be exhausted or recirculated.
Besides removing particulates from the source of the pollution, it can also be cleaned in
the open air.==Climate effects==Atmospheric aerosols affect the climate of
the earth by changing the amount of incoming solar radiation and outgoing terrestrial longwave
radiation retained in the earth’s system. This occurs through several distinct mechanisms
which are split into direct, indirect and semi-direct aerosol effects. The aerosol climate
effects are the biggest source of uncertainty in future climate predictions. The Intergovernmental
Panel on Climate Change, Third Assessment Report, says: While the radiative forcing
due to greenhouse gases may be determined to a reasonably high degree of accuracy…
the uncertainties relating to aerosol radiative forcings remain large, and rely to a large
extent on the estimates from global modelling studies that are difficult to verify at the
present time.===Aerosol radiative effects=======
Direct effect====The direct aerosol effect consists of any
direct interaction of radiation with atmospheric aerosols, such as absorption or scattering.
It affects both short and longwave radiation to produce a net negative radiative forcing.
The magnitude of the resultant radiative forcing due to the direct effect of an aerosol is
dependent on the albedo of the underlying surface, as this affects the net amount of
radiation absorbed or scattered to space. e.g. if a highly scattering aerosol is above
a surface of low albedo it has a greater radiative forcing than if it was above a surface of
high albedo. The converse is true of absorbing aerosol, with the greatest radiative forcing
arising from a highly absorbing aerosol over a surface of high albedo. The direct aerosol
effect is a first order effect and is therefore classified as a radiative forcing by the IPCC.
The interaction of an aerosol with radiation is quantified by the single-scattering albedo
(SSA), the ratio of scattering alone to scattering plus absorption (extinction) of radiation
by a particle. The SSA tends to unity if scattering dominates, with relatively little absorption,
and decreases as absorption increases, becoming zero for infinite absorption. For example,
the sea-salt aerosol has an SSA of 1, as a sea-salt particle only scatters, whereas soot
has an SSA of 0.23, showing that it is a major atmospheric aerosol absorber.====Indirect effect====
The Indirect aerosol effect consists of any change to the earth’s radiative budget due
to the modification of clouds by atmospheric aerosols, and consists of several distinct
effects. Cloud droplets form onto pre-existing aerosol particles, known as cloud condensation
nuclei (CCN). For any given meteorological conditions, an
increase in CCN leads to an increase in the number of cloud droplets. This leads to more
scattering of shortwave radiation i.e. an increase in the albedo of the cloud, known
as the Cloud albedo effect, First indirect effect or Twomey effect. Evidence supporting
the cloud albedo effect has been observed from the effects of ship exhaust plumes and
biomass burning on cloud albedo compared to ambient clouds. The Cloud albedo aerosol effect
is a first order effect and therefore classified as a radiative forcing by the IPCC.An increase
in cloud droplet number due to the introduction of aerosol acts to reduce the cloud droplet
size, as the same amount of water is divided into more droplets. This has the effect of
suppressing precipitation, increasing the cloud lifetime, known as the cloud lifetime
aerosol effect, second indirect effect or Albrecht effect. This has been observed as
the suppression of drizzle in ship exhaust plume compared to ambient clouds, and inhibited
precipitation in biomass burning plumes. This cloud lifetime effect is classified as a climate
feedback (rather than a radiative forcing) by the IPCC due to the interdependence between
it and the hydrological cycle. However, it has previously been classified as a negative
radiative forcing.====Semi-direct effect====
The Semi-direct effect concerns any radiative effect caused by absorbing atmospheric aerosol
such as soot, apart from direct scattering and absorption, which is classified as the
direct effect. It encompasses many individual mechanisms, and in general is more poorly
defined and understood than the direct and indirect aerosol effects. For instance, if
absorbing aerosols are present in a layer aloft in the atmosphere, they can heat surrounding
air which inhibits the condensation of water vapour, resulting in less cloud formation.
Additionally, heating a layer of the atmosphere relative to the surface results in a more
stable atmosphere due to the inhibition of atmospheric convection. This inhibits the
convective uplift of moisture, which in turn reduces cloud formation. The heating of the
atmosphere aloft also leads to a cooling of the surface, resulting in less evaporation
of surface water. The effects described here all lead to a reduction in cloud cover i.e.
an increase in planetary albedo. The semi-direct effect classified as a climate feedback) by
the IPCC due to the interdependence between it and the hydrological cycle. However, it
has previously been classified as a negative radiative forcing.===Roles of different aerosol species=======
Sulfate aerosol====Sulfate aerosol has two main effects, direct
and indirect. The direct effect, via albedo, is a cooling effect that slows the overall
rate of global warming: the IPCC’s best estimate of the radiative forcing is −0.4 watts per
square meter with a range of −0.2 to −0.8 W/m² but there are substantial uncertainties.
The effect varies strongly geographically, with most cooling believed to be at and downwind
of major industrial centres. Modern climate models addressing the attribution of recent
climate change take into account sulfate forcing, which appears to account (at least partly)
for the slight drop in global temperature in the middle of the 20th century. The indirect
effect (via the aerosol acting as cloud condensation nuclei, CCN, and thereby modifying the cloud
properties -albedo and lifetime-) is more uncertain but is believed to be a cooling.====Black carbon====
Black carbon (BC), or carbon black, or elemental carbon (EC), often called soot, is composed
of pure carbon clusters, skeleton balls and buckyballs, and is one of the most important
absorbing aerosol species in the atmosphere. It should be distinguished from organic carbon
(OC): clustered or aggregated organic molecules on their own or permeating an EC buckyball.
BC from fossil fuels is estimated by the IPCC in the Fourth Assessment Report of the IPCC,
4AR, to contribute a global mean radiative forcing of +0.2 W/m² (was +0.1 W/m² in the
Second Assessment Report of the IPCC, SAR), with a range +0.1 to +0.4 W/m². Bond et al.,
however, states that “the best estimate for the industrial-era (1750 to 2005) direct radiative
forcing of atmospheric black carbon is +0.71 W/m² with 90% uncertainty bounds of (+0.08,
+1.27) W/m²” with “total direct forcing by all black carbon sources, without subtracting
the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W/m²”===Instances of aerosol affecting climate
===Volcanoes are a large natural source of aerosol
and have been linked to changes in the earth’s climate often with consequences for the human
population. Eruptions linked to changes in climate include the 1600 eruption of Huaynaputina
which was linked to the Russian famine of 1601 – 1603, leading to the deaths of two
million, and the 1991 eruption of Mount Pinatubo which caused a global cooling of approximately
0.5 °C lasting several years. Research tracking the effect of light-scattering aerosols in
the stratosphere during 2000 and 2010 and comparing its pattern to volcanic activity
show a close correlation. Simulations of the effect of anthropogenic particles showed little
influence at present levels.Aerosols are also thought to affect weather and climate on a
regional scale. The failure of the Indian Monsoon has been linked to the suppression
of evaporation of water from the Indian Ocean due to the semi-direct effect of anthropogenic
aerosol.Recent studies of the Sahel drought and major increases since 1967 in rainfall
over the Northern Territory, Kimberley, Pilbara and around the Nullarbor Plain have led some
scientists to conclude that the aerosol haze over South and East Asia has been steadily
shifting tropical rainfall in both hemispheres southward.The latest studies of severe rainfall
decline over southern Australia since 1997 have led climatologists there to consider
the possibility that these Asian aerosols have shifted not only tropical but also midlatitude
systems southward.==Health effects=====Size, shape and solubility matter===
The size of the particle is a main determinant of where in the respiratory tract the particle
will come to rest when inhaled. Larger particles are generally filtered in the nose and throat
via cilia and mucus, but particulate matter smaller than about 10 micrometers, can settle
in the bronchi and lungs and cause health problems. The 10-micrometer size does not
represent a strict boundary between respirable and non-respirable particles, but has been
agreed upon for monitoring of airborne particulate matter by most regulatory agencies. Because
of their small size, particles on the order of 10 micrometers or less (coarse particulate
matter, PM10) can penetrate the deepest part of the lungs such as the bronchioles or alveoli;
when asthmatics are exposed to these conditions it can trigger bronchoconstrictionSimilarly,
so called fine particulate matter (PM2.5), tend to penetrate into the gas exchange regions
of the lung (alveolus), and very small particles (ultrafine particulate matter, PM0.1) may
pass through the lungs to affect other organs. Penetration of particles is not wholly dependent
on their size; shape and chemical composition also play a part. To avoid this complication,
simple nomenclature is used to indicate the different degrees of relative penetration
of a PM particle into the cardiovascular system. Inhalable particles penetrate no further than
the bronchi as they are filtered out by the cilia. Thoracic particles can penetrate right
into terminal bronchioles whereas PM0.1, which can penetrate to alveoli, the gas exchange
area, and hence the circulatory system are termed respirable particles.
In analogy, the inhalable dust fraction is the fraction of dust entering nose and mouth
which may be deposited anywhere in the respiratory tract. The thoracic fraction is the fraction
that enters the thorax and is deposited within the lung’s airways. The respirable fraction
is what is deposited in the gas exchange regions (alveoli).The smallest particles, less than
100 nanometers (nanoparticles), may be even more damaging to the cardiovascular system.
Nanoparticles can pass through cell membranes and migrate into other organs, including the
brain. Particles emitted from modern diesel engines (commonly referred to as Diesel Particulate
Matter, or DPM) are typically in the size range of 100 nanometers (0.1 micrometer).
These soot particles also carry carcinogens like benzopyrenes adsorbed on their surface.
Particulate mass is not a proper measure of the health hazard, because one particle of
10 μm diameter has approximately the same mass as 1 million particles of 100 nm diameter,
but is much less hazardous, as it is unlikely to enter the alveoli. Legislative limits for
engine emissions based on mass are therefore not protective. Proposals for new regulations
exist in some countries, with suggestions to limit the particle surface area or the
particle count (numerical quantity) instead.The site and extent of absorption of inhaled gases
and vapors are determined by their solubility in water. Absorption is also dependent upon
air flow rates and the partial pressure of the gases in the inspired air. The fate of
a specific contaminant is dependent upon the form in which it exists (aerosol or particulate).
Inhalation also depends upon the breathing rate of the subject.Another complexity not
entirely documented is how the shape of PM can affect health, except for the needle-like
shape of asbestos which can lodge itself in the lungs. Geometrically angular shapes have
more surface area than rounder shapes, which in turn affects the binding capacity of the
particle to other, possibly more dangerous substances.===Health problems===The effects of inhaling particulate matter
that has been widely studied in humans and animals include asthma, lung cancer, respiratory
diseases, cardiovascular disease, premature delivery, birth defects, low birth weight,
and premature death. Inhalation of PM2.5 – PM10 is associated
with elevated risk of adverse pregnancy outcomes, such as low birth weight . Maternal PM2.5
exposure during pregnancy is also associated with high blood pressure in children. Exposure
to PM2.5 has been associated with greater reductions in birth weight than exposure to
PM10. PM exposure can cause inflammation, oxidative stress, endocrine disruption, and
impaired oxygen transport access to the placenta, all of which are mechanisms for heightening
the risk of low birth weight. Overall epidemiologic and toxicological evidence suggests that a
causal relationship exists between long-term exposures to PM2.5 and developmental outcomes
(i.e. low birth weight). However, studies investigating the significance of trimester-specific
exposure have proven to be inconclusive, and results of international studies have been
inconsistent in drawing associations of prenatal particulate matter exposure and low birth
weight. As perinatal outcomes have been associated with lifelong health and exposure to particulate
matter is widespread, this issue is of critical public health importance and additional research
will be essential to inform public policy on the matter.
Increased levels of fine particles in the air as a result of anthropogenic particulate
air pollution “is consistently and independently related to the most serious effects, including
lung cancer and other cardiopulmonary mortality.” A large number of deaths and other health
problems associated with particulate pollution was first demonstrated in the early 1970s
and has been reproduced many times since. PM pollution is estimated to cause 22,000–52,000
deaths per year in the United States (from 2000) contributed to ~370,000 premature deaths
in Europe during 2005. and 3.22 million deaths globally in 2010 per the global burden of
disease collaboration.A 2002 study indicated that PM2.5 leads to high plaque deposits in
arteries, causing vascular inflammation and atherosclerosis – a hardening of the arteries
that reduces elasticity, which can lead to heart attacks and other cardiovascular problems.
A 2014 meta analysis reported that long term exposure to particulate matter is linked to
coronary events. The study included 11 cohorts participating in the European Study of Cohorts
for Air Pollution Effects (ESCAPE) with 100,166 participants, followed for an average of 11.5
years. An increase in estimated annual exposure to PM 2.5 of just 5 μg/m3 was linked with
a 13% increased risk of heart attacks. In 2017 a study revealed that PM not only affects
human cells and tissues, but also impacts bacteria which cause disease in humans. This
study concluded that biofilm formation, antibiotic tolerance, and colonisation of both Staphylococcus
aureus and Streptococcus pneumoniae was altered by Black Carbon exposure.
The World Health Organization (WHO) estimated in 2005 that “… fine particulate air pollution
(PM(2.5)), causes about 3% of mortality from cardiopulmonary disease, about 5% of mortality
from cancer of the trachea, bronchus, and lung, and about 1% of mortality from acute
respiratory infections in children under 5 years, worldwide.”. A 2011 study concluded
that traffic exhaust is the single most serious preventable cause of heart attack in the general
public, the cause of 7.4% of all attacks.The largest US study on acute health effects of
coarse particle pollution between 2.5 and 10 micrometers in diameter. was published
2008 and found an association with hospital admissions for cardiovascular diseases but
no evidence of an association with the number of hospital admissions for respiratory diseases.
After taking into account fine particle levels (PM2.5 and less), the association with coarse
particles remained but was no longer statistically significant, which means the effect is due
to the subsection of fine particles. Particulate matter studies in Bangkok Thailand
from 2008 indicated a 1.9% increased risk of dying from cardiovascular disease, and
1.0% risk of all disease for every 10 micrograms per cubic meter. Levels averaged 65 in 1996,
68 in 2002, and 52 in 2004. Decreasing levels may be attributed to conversions of diesel
to natural gas combustion as well as improved regulations.The Mongolian government agency
recorded a 45% increase in the rate of respiratory illness in the past five years (reported in
September 2014). Bronchial asthma, chronic obstructive pulmonary disease and interstitial
pneumonia were the most common ailments treated by area hospitals. Levels of premature death,
chronic bronchitis, and cardiovascular disease are increasing at a rapid rate.A study In
2000 conducted in the U.S. explored how fine particulate matter may be more harmful than
coarse particulate matter. The study was based on six different cities. They found that deaths
and hospital visits that were caused by particulate matter in the air were primarily due fine
particulate matter.==Effects on vegetation==
Particulate matter can clog stomatal openings of plants and interfere with photosynthesis
functions. In this manner, high particulate matter concentrations in the atmosphere can
lead to growth stunting or mortality in some plant species.==Regulation==
Due to the highly toxic health effects of particulate matter, most governments have
created regulations both for the emissions allowed from certain types of pollution sources
(motor vehicles, industrial emissions etc.) and for the ambient concentration of particulates.
The IARC and WHO designate particulates a Group 1 carcinogen. Particulates are the deadliest
form of air pollution due to their ability to penetrate deep into the lungs and blood
streams unfiltered, causing permanent DNA mutations, heart attacks and premature death.
In 2013, the ESCAPE study involving 312,944 people in nine European countries revealed
that there was no safe level of particulates and that for every increase of 10 μg/m3 in
PM10, the lung cancer rate rose 22%. For PM2.5 there was a 36% increase in lung cancer per
10 μg/m3. In a 2014 meta-analysis of 18 studies globally including the ESCAPE data, for every
increase of 10 μg/m3 in PM2.5, the lung cancer rate rose 9%.===Australia===
Australia has set limits for particulates in the air:===Canada===
In Canada the standard for particulate matter is set nationally by the federal-provincial
Canadian Council of Ministers of the Environment (CCME). Jurisdictions (provinces and territories)
may set more stringent standards. The CCME standard for particulate matter 2.5 (PM2.5)
as of 2015 is 28 μg/m3 (calculated using the 3-year average of the annual 98th percentile
of the daily 24-hr average concentrations) and 10 μg/m³ (3-year average of annual mean).
PM2.5 standards will increase in stringency in 2020.===China===
China has set limits for particulates in the air:===European Union===
The European Union has established the European emission standards, which include limits for
particulates in the air:===Hong Kong===
Hong Kong has set limits for particulates in the air:===Japan===
Japan has set limits for particulates in the air:===South Korea===
South Korea has set limits for particulates in the air:===Taiwan===
Taiwan has set limits for particulates in the air:===United States===
The United States Environmental Protection Agency (EPA) has set standards for PM10 and
PM2.5 concentrations. (See National Ambient Air Quality Standards)====California====In October 2008, the Department of Toxic Substances
Control (DTSC), within the California Environmental Protection Agency, announced its intent to
request information regarding analytical test methods, fate and transport in the environment,
and other relevant information from manufacturers of carbon nanotubes. DTSC is exercising its
authority under the California Health and Safety Code, Chapter 699, sections 57018-57020.
These sections were added as a result of the adoption of Assembly Bill AB 289 (2006). They
are intended to make information on the fate and transport, detection and analysis, and
other information on chemicals more available. The law places the responsibility to provide
this information to the Department on those who manufacture or import the chemicals.
On 22 January 2009, a formal information request letter was sent to manufacturers who produce
or import carbon nanotubes in California, or who may export carbon nanotubes into the
State. This letter constitutes the first formal implementation of the authorities placed into
statute by AB 289 and is directed to manufacturers of carbon nanotubes, both industry and academia
within the State, and to manufacturers outside California who export carbon nanotubes to
California. This request for information must be met by the manufacturers within one year.
DTSC is waiting for the upcoming 22 January 2010 deadline for responses to the data call-in.
The California Nano Industry Network and DTSC hosted a full-day symposium on 16 November
2009 in Sacramento, CA. This symposium provided an opportunity to hear from nanotechnology
industry experts and discuss future regulatory considerations in California.DTSC is expanding
the Specific Chemical Information Call-in to members of the nanometal oxides, the latest
information can be found on their website.====Colorado====Key points in the Colorado Plan include reducing
emission levels and solutions by sector. Agriculture, transportation, green electricity, and renewable
energy research are the main concepts and goals in this plan. Political programs such
as mandatory vehicle emissions testing and the prohibition of smoking indoors are actions
taken by local government to create public awareness and participation in cleaner air.
The location of Denver next to the Rocky Mountains and wide expanse of plains makes the metro
area of Colorado’s capital city a likely place for smog and visible air pollution.==Affected areas==The most concentrated particulate matter pollution
resulting from the burning of fossil fuels by transportation and industrial sources tends
to be in densely populated metropolitan areas in developing countries such as Delhi and
Beijing.===Australia===
PM10 pollution in coal mining areas in Australia such as the Latrobe Valley in Victoria and
the Hunter Region in New South Wales significantly increased during 2004 to 2014. Although the
increase did not significantly add to non-attainment statistics the rate of increase has risen
each year during 2010 to 2014.===China===
Some cities in Northern China and South Asia have had concentrations above 200 μg/m3 up
to a few years ago. The PM levels in Chinese cities have been extreme in recent years,
reaching an all-time high in Beijing on 12 January 2013, of 993 μg/m3.To monitor the
air quality of south China, the U.S. Consulate Guangzhou set a PM 2.5 monitor on Shamian
Island in Guangzhou, and displays readings on its official website and social platforms.===Ulaanbaatar===
Mongolia’s capital city Ulaanbaatar has an annual average mean temperature of about 0
°C, making it the world’s coldest capital city. About 40% of the population lives in
apartments, 80% of which are supplied with central heating systems from 3 combined heat
and power plants. In 2007, the power plants consumed almost 3.4 million tons of coal.
The pollution control technology is in poor condition.The other 60% of the population
reside in shantytowns (Ger districts), which have developed due to the country’s new market
economy and the very cold winter seasons. The poor in these districts cook and heat
their wood houses with indoor stoves fueled by wood or coal. The resulting air pollution
is characterized by raised sulfur dioxide and nitrogen oxide levels and very high concentrations
of airborne particles and particulate matter (PM).
Annual seasonal average particulate matter concentrations have been recorded as high
as 279 μg/m3 (micrograms per cubic meter). The World Health Organization’s recommended
annual mean PM10 level is 20 μg/m3, which means that Ulaanbaatar’s PM10 annual mean
levels are 14 times higher than recommended.During the winter months in particular, the air pollution
obscures the air, affecting the visibility in the city to such an extent that airplanes
on some occasions are prevented from landing at the airport.In addition to stack emissions,
another source unaccounted for in the emission inventory is fly ash from ash ponds, the final
disposal place for fly ash that has been collected in settling tanks. Ash ponds are continually
eroded by wind during the dry season.==See also====Notes

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