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Air Pollution - Monitoring Particulates

Published: 10th Dec 2009 in AWE International

air-pollution2.jpg, Air Pollution - Monitoring Particulates, Gary Noakes, Casella Measurement, AWE International

Clean air is an essential requirement for the health and wellbeing of both the human race and the environment we live in, but achieving it is a constant battle with air pollution. According to the World Health Organisation (WHO), more than two million premature deaths each year can be attributed to the effects of urban outdoor and indoor air pollution, a shocking statistic indeed.

Despite encouraging news of improvements in the emission of air pollutants in Europe in 2007, the latest emissions estimates for 2010 from the European Environment Agency (EEA) show that only half of EU members (14 Member States) expect to meet their 2010 air pollutant limits as set under the EU National Emission Ceilings Directive.

France, Germany, Spain and the Netherlands anticipate missing two or more of the legally-binding emission ceilings for sulphur dioxide (SO2), nitrogen oxides (NOx), non-methane volatile organic compounds (NMVOCs) and ammonia (NH3). These pollutants are harmful to both human health and our surroundings, including crops, ecosystems and infrastructure, by contributing to the formation of ground-level ozone and particulate matter.

Particulate matter

Particulate matter (PM) consists of microscopic solid and liquid particles that remain suspended in both indoor and outdoor air over a period of time and seriously damage human health and the environment. First identified in the 1950s, particulates emanate from both natural and man-made sources and have primary as well as secondary causes. Particulate matter from natural sources, including pollen, soil erosion, forest fires, volcanoes, and dust storms, is generally composed of larger solid particles that, although considered a nuisance, are less likely to enter the lungs by inhalation. Anthropomorphic particles, which arise from human activity, however, range in size from ultra-fine sub-micro, to coarse particles.

Primary sources of PM, where it is directly emitted into the atmosphere, include both natural and human-activity sources, such as fuel combustion, surface erosion, wind-blown dusts and quarrying or demolition. During demolition and construction, a variety of dusts is generated, and some form of dust is produced from nearly every activity. Some of the most hazardous dust types include asbestos, crystalline silica and wood dust. Other particulates may include welding fumes, moulds, chemicals and paint fumes.

“particulate matter consists of microscopic solid and liquid particles that remain suspended in air and seriously damage human health and the environment”

Secondary particulates arise when PM is formed in the atmosphere through reaction with other pollutants such as sulphur dioxide, nitrogen oxides and ammonia, to form solid sulphates and nitrates. Regular and robust monitoring and measuring of these pollutants is essential to prevent further damage to wellbeing and environment.

Classification of particles

Particles vary in size, number, toxicity and chemical composition. They can be classified into fractions in terms of their size when emitted to air, according to ISO standard 7708 on Air Quality, a standard used in assessing the possible health effects of airborne particles in the workplace and ambient environment. As particles are often nonspherical, such as asbestos fibres for example, there are many definitions of particle size, the most widely used of which is the aerodynamic diameter. The annotation PM10 is used to describe particles of 10 micrometres or less, such as soot, dust, pollen and spores, while PM2.5 represents finer particles measuring 2.5 micrometres or less in aerodynamic diameter, that are often formed from gases.

The smaller and lighter a particulate, the longer it will stay in the atmosphere - the smallest particles of less than 1 micrometre in diameter can remain in the air for weeks until they are washed down by rain, whereas particles of greater than 10 micrometres tend to gravitate to the ground relatively rapidly.

The size of the particle also determines the location in the human body where it may come to rest if inhaled. Larger particles are generally filtered by hairs in the nose and throat so do not penetrate to the deepest part of the lungs, whilst smaller particulates below 10 micrometres in diameter can settle deep in the bronchi and lungs and cause both acute and chronic respiratory problems. It is possible that extremely small particles are able to pass through cell membranes into the brain itself, causing brain damage.

Sources of particulates

The main sources of primary PM10 and PM2.5 from human activity are:

• Exponentially-increasing motor vehicle emissions, especially from diesel-burning engines, which emit a greater mass of particulates per vehicle kilometre than petrol engines; brake and tyre wear on all vehicles; and air turbulence generated by vehicles. Trains and especially ships also generate considerable particulate pollution

• Household energy use. The combustion of coal, wood, gas and fuel oil all produce PMs, although the domestic use of coal in the UK has lessened considerably over the last 40 years

• Industrial processes such as power generation from fossil fuels, incineration, stone crushing, bulk handling of dusty materials, minerals processing, cement, lime, coke and chemical production, construction, mining, quarrying and iron and steel production

Fine secondary aerosols generated as a result of condensation or photochemical reactions of gaseous air pollutants also contribute to PM10 and PM2.5 levels.

Quarrying and demolition generate PM ranging from coarse to fine particles, while combustion processes involving high temperatures, power generation and motor vehicles produce mainly fine and ultra-fine particles (PM0.1).

The law

EU air quality legislation sets two legally binding limit values for PM10 mass concentrations:

• Annual mean levels exceeding 40 μg PM10 per cubic metre

• Exceeding 50 μg cubic metre on more than 35 days per year

A new Air Quality Directive for Europe (2008/50/EC) came into force in June 2008 merging existing Directives into a single Directive on air quality. By law it must be transposed by member states into national legislation by 10 June 2010. In the UK, the Department for Environment Food and Rural Affairs (Defra) is currently consulting on this transposition. For the first time, the Directive set legally binding limit values for PM2.5 levels to be attained in 2015. Under the Directive, Member States are required to reduce exposure to PM2.5 in urban areas by an average of 20% by 2020 based on 2010 levels. It obliges them to bring exposure levels below 20 micrograms/m3 by 2015 in these areas. 

air-quality.jpg, source testing, AWE International magazine, Gary Noakes, Casella Measurement,

The UK government has implemented the requirements of the EC directives - as well as its own specific objectives and targets - through the UK regulatory framework and the National Air Quality Strategy (NAQS), which was first published in 1997 and amended in July 2007 to become the Air Quality Standards Regulations 2007.

Current European position

The EEA reported in March 2009 that particulate matter and groundlevel ozone remain significant air pollutants in Europe. Despite improvements due to EU legislation, they continue to exact a heavy toll on human health, especially in southern and eastern Europe. Across the EU, PM10 is estimated to have caused approximately 373,000 premature deaths in 2005.

One in four Europeans endured many days of frequent and high concentrations of PM10 in 2005, according to the EEA. In addition, one in ten Europeans was exposed to persistent PM10 levels higher than the EU’s annual mean limit. Large areas of eastern Europe and the Po Valley in northern Italy and parts of the Balkans, Belgium, Greece, Italy, Luxembourg, the Netherlands, Portugal and Spain were particularly likely to record daily levels of PM and ozone above the limit, especially in more urbanised environments. Urban areas of the Balkans, the Czech Republic, Hungary, southern Poland and southern Spain were especially likely to report excessive levels throughout the year.

The top polluting sources in the 27 countries of the European Union in 2007 were fuel combustion in households, passenger cars, heavy duty vehicles, and power plants. Emissions of fine particulate matter (PM2.5) have decreased by 2% compared to those in 2006 and by about 12% since the year 2000. However, the EEA warns, the reporting of PM emissions from Member States is less complete than for the other main pollutants. France, Germany, Italy, Poland, Spain and the United Kingdom contributed the most to EU-27 emissions in 2007.

In the UK, emissions of PM10 declined by 52% over the period 1990 to 2007, reflecting reduced use of coal, particularly by domestic users. However, coal combustion still contributed 10% of UK emissions of PM10 in 2007, whilst road transport sources contributed a further 18%.

The House of Commons Environmental Audit Committee launched a new inquiry in October into UK air quality to assess whether the Government has an effective strategy for meeting the requirements of EU air quality legislation. In preparation for the inquiry, it has also commissioned an overview report on the UK’s performance to date in meeting the targets from the National Audit Office.

The latest Government strategy for air UK quality, published in 2007, recognises that air pollution is estimated to reduce the life expectancy of every person in the UK by an average of 7 to 8 months, and cost up to £20 billion every year in expenditure on health. Despite this, the UK has failed to meet the target for particulate matter (PM10) under the EU Air Quality Framework Directive.

“there is a plethora of new detailed scientific research evidence which has ongoing implications for air quality monitoring and guidelines”

New research

There is a plethora of new detailed scientific research evidence using ever-more sensitive indicators on the health effects of air pollution, which has ongoing implications for air quality monitoring and guidelines. According to the WHO, this research has made a number of important discoveries. It has found that the current concentrates of ozone and particulates in many urban environments in developed countries are a risk to human health and that no thresholds have been identified below which adverse effects do not occur, meaning that any pollution is bad pollution.

Evidence also points to an increasing range of adverse health effects linked to air pollution, especially of airborne PM, and at lower concentrations than was previously thought. New studies use more refined methods and more subtle but sensitive indicators of effects, including physiological measures such as changes in lung function and inflammation markers (which can indicate that an individual is at a high risk of a fatal heart attack or stroke), as well as statistics on mortality and hospital admissions.

“exposure to fine particulate matter in outdoor air leads to about 100,000 deaths a year in Europe”

The WHO reports serious risks to health from exposure to PM and ozone in many cities in both developed and developing countries, stating that there is a quantitative relationship between pollution levels and increased mortality or disease, even at relatively low concentrations.

Effects on human health

It has been estimated by the WHO in its World Health Report that exposure to fine particulate matter in outdoor air leads to about 100,000 deaths a year in Europe2 and this does not take account of its presence in indoor air. The effects of inhaling particulate matter have been widely studied in both humans and animals. Adverse health effects include asthma, emphysema, lung cancer, farmer’s lung (shortness of breath and weight loss), cardiovascular disease, increased hospital admission and premature death. Children, older people and those with respiratory illnesses are especially at risk.

According to the WHO, long-term exposure to current ambient PM concentrations may lead to a marked reduction in life expectancy, primarily due to increased cardio-pulmonary and lung cancer mortality. Increases are likely in lower respiratory symptoms and reduced lung function in children, and chronic obstructive pulmonary disease and reduced lung function in adults.3

Air-Pollution.jpg, Monitoring Particulates, AWE International, Gary Noakes, Casella Measurement

“emissions are difficult to destroy and can be blown over hundreds or even thousands of miles by wind currents, even affecting different countries”

A recent US study undertaken reported in the New England Journal of Medicine4 found that a reduction in exposure to ambient fineparticulate air pollution contributed to an improvement of almost 5 months in life expectancy in the United States between 1980 and 2000. Scientists found people were living 2.72 years longer by 2000 - 15% of which increase they attributed to falls in pollution. In another study reported in the same Journal5, investigators found that a decrease in the concentration of PM2.5 of 10 µg per cubic metre was associated with an increase in life expectancy of 0.77 years.

Transboundary pollution

Air pollution knows no boundaries and is to some extent outside of our control. Emissions are difficult to destroy and can be blown over hundreds or even thousands of miles by wind currents, affecting people and places far away from the original source and even in different countries, as demonstrated by the pollutants from forest fires in Quebec in 2002 that significantly affected people living over 700 miles away.

Because pollution is transboundary, there is no clear relationship between how much pollution a country exports and how much it imports from other countries. For example, since the prevailing wind direction is generally westerly or south westerly, much of the pollution emitted in the UK travels across the North Sea and is deposited in Scandinavia, where it produces acid rain, while the UK in its turn receives pollutants from other countries such as France.

Inside and out

Outdoor air pollution is a serious problem in cities throughout the world, particularly in the megacities of developing countries. The WHO estimates that a quarter of the world’s population is exposed to unhealthy concentrations of air pollutants. But the quality of the air located outdoors inevitably affects the quality of the air indoors and the risks to health are the same whether the air is inhaled inside a home or workplace or in the ambient environment. Research taking place on pollutants including particulate matter in both areas is now inextricably linked.

Hazardous air quality is an issue in traditional factories or industries, where dust is created by grinding or processing, for example, and gases generated as by-products of industrial processes, but pollution can also exist in indoor environments such as offices, where it can contribute to loss of productivity, comfort and wellbeing of staff and lead to a risk of fire or explosion. Air conditioning systems that are supposed to ‘clean’ the air may actually draw in polluted particlecontaining air, such as from traffic, from outside, so particulates, NOx and other toxic gases and solvents may be just as prevalent in offices as factories.

Indoor pollutants kill around 1.6 million people every year, according to WHO estimates, while poor indoor air quality may pose a risk to the health of over half of the world’s population. The majority of human exposure to air pollution takes place in indoor environments, particularly those that are poorly ventilated, where people spend most of their time. Air coming into the workplace will already contain pollutants, to which are added particles, chemicals and gases that emanate from indoor sources, at much higher concentrations. Sickbuilding syndrome is a well-known phenomenon, reported when those working or living within it have a wide range of ailments related to poor indoor air quality, such as nose and throat problems, skin irritations and general malaise.

NOx and other harmful inhalable substances such as dusts, fumes, vapours, fibres, gases and micro-organisms are hazards also likely to be faced in workplace air both indoors and outdoors in many industries, processes, or environments, such as the automotive industry, energy industries, iron and steel, petroleum refining, chemical, cement and paper industries, and rail, air and marine transport.

Indoor air monitoring

A wide variety of instruments and equipment is available to take readings and air samples from indoor environments, including particulate samplers or sampling pumps. Measuring and monitoring of indoor air can be done by the wearing of personal air sampling equipment or by remote measuring and monitoring (telemetry) of indoor air.

To measure the effects of particulates, a sampling regime for personal and ambient dust levels may be put in place, so that appropriate control measures can be implemented to keep the levels in check. For personal exposure monitoring, personal air sampling pumps, such as Casella’s Apex, can be used to collect samples onto filter media over an 8 hour exposure, before being sent off for gravimetric or chemical speciation. As well as detecting dust and PM10 levels over a period of time, these pollutants can also be pinpointed in real time to highlight specific activities, such as the use of grinding discs, by instruments such as Casella’s Microdust Pro, which provides instantaneous dust readings every second.

Simple gravimetric sampling, where volumes of air are drawn through a filter, is considered to be the most accurate method and produces concentrations equivalent to EU reference samplers, used to set EU limit values. Such systems have designated inlet heads to measure different particulate fractions and a typical measurement is taken over 24 hours.

Ambient air monitoring

National and local air quality monitoring networks have been set up in the UK to collect and share data to provide an overall picture of pollution. There are over 1500 air quality monitoring points in the UK, organised into information-gathering networks, where groups of local authorities make their air quality data available for other authorities to download, under the auspices of Defra. The particulate monitoring network provides data on the chemical composition of particulate matter, primarily for the use of researchers of atmospheric processes, epidemiology and toxicology.


While the risks to health and the environment from air pollution are undoubted, a planned and effective monitoring strategy allows the impact from particulate and other pollution to be assessed and controlled. Regular and accurate air quality monitoring in the workplace is essential to inform people when they are at risk, and to enable effective emission control procedures to be put in place for any activity that generates dust or particulates. Air quality monitoring can measure the extent of exposure, as well as the effectiveness of any control measures already in place, so that appropriate risk management strategies can be formulated. In the ambient environment, regular monitoring plays a role in spurring regulators and industry to take protective, mitigating, or evasive action when pollution levels get too high. Monitoring is also essential to ensure that air quality meets UK and EU targets.


1. WHO Air Quality Guidelines, Global Update 2005


3 WHO Health Aspects of Air Pollution (2003)

4 Fine-Particulate Air Pollution and Life Expectancy in the United States, January 2009 (NEJM)

5 Evaluating the Effects of Ambient Air Pollution on Life Expectancy, January 2009 (NEJM)


Gary Noakes

Tel: +44 (0)1234 844100 

Published: 10th Dec 2009 in AWE International


Gary Noakes

Gary Noakes is Product Manager with Casella Measurement, which manufactures a wide range of measuring technology for industrial, environmental and occupational hygiene and safety markets around the world. The company manufactures a range of personal air sampling pumps which includes the Vortex Ultra Flow Sampling pump, which is used in asbestos monitoring applications.


Gary Noakes



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