Indoor Air Pollution Overview

Cigarette Smoke

It is worth noting that the health effects of the above indoor pollutants are small when compared to the health effects of smoking. Cigarettes themselves contribute to a sizeable decrease in indoor air quality. PM10 pollution is around 3 times higher in homes occupied by smokers. In the US, 3000 people die each year from passive smoking alone. In the UK, the story is not as bad as would seem. Between 1965 and 1995, annual cigarette sales have fallen from 150 billion to 8 billion. This decrease in sales has resulted in a halving of tobacco-related deaths in middle-aged men (aged 35-69) from 80,000 to 40,000 a year. (Peto et al) There is also likely to be a knock-on effect on deaths in old age due to the decrease in popularity of cigarettes. However, tobacco firms shouldn't yet be written off. Eight million people are expected to die from smoking in the year 2020, and as attitudes towards smoking change in the West, developing countries are increasingly being targeted. Already the vast majority of smokers live in developing countries (800million out of 1.1billion worldwide) (WHO). In fact, within 25 years, it is estimated that tobacco will surpass infectious diseases to become the leading threat to human health (Murray and Lopez). Currently, the global cost of tobacco-related illnesses is nearly $200 billion a year in direct health-care expenses and lost productivity related to morbidity and premature mortality. One third of this loss occurs in the developing world.
Due to the high death rates caused by smoking, measures which limit cigarette consumption would result in a huge gain to society, both in terms of human life and expenditure in health care, but unfortunately there is nothing to be gained by monitoring levels of cigarette smoke in homes. The adverse health effects caused by smoking are well known by the vast majority of the population and in the UK measures to limit the consumption of cigarettes have been successful to a certain degree. Smoking, though dangerous, is seen by many as a lifestyle choice and it would therefore be more beneficial to provide information on another form of indoor air "pollution".

Asbestos fibres

Asbestos is an inexpensive, strong and heat proof mineral fibre which was used extensively in the 1960s in a number of products from pipe and furnace materials to textured paints and floor tiles. In the mid 70s the risk to building occupants and asbestos workers in particular was discovered and the material was banned in the mid 70s in a number of countries.
Intact, asbestos does not affect human health. However, when damaged, the fibres can become airborne and lodge in the lungs and airways. The health effects of continued exposure are lung cancer or asbestosis, loss in breathing capacity due to scaring of lung tissue caused by fibre damage.

Viability of air quality service for asbestos fibres

Asbestos fibres can only be identified under a microscope, therefore an information service could not be implemented. Although asbestos fibres represent a considerable risk to the building occupant, they are only produced in asbestos is present in a damaged state. The remedial measures therefore include the inspection or removal of the asbestos, not air quality monitoring.

PM10s

Particulate Matter of fewer than 10 microns diameter is referred to as PM10. This includes dust, dirt, smoke, soot and other outdoor air pollution, deposited into the atmosphere by industry and transport. They can also be formed through condensation of pollutants such as nitrogen oxide.
PM10s are well known to be the biggest danger to human health of all pollutants, as long-term exposure has serious effects on respiration. Upon entry to the respiratory system some PM10s can cause damage to lung tissue and some are thought to cause cancer. However, the reason they do this is not fully understood.
Additionally, PM10s attributed to living organisms such as mould, dust mites and plants can cause allergic reactions and adverse health effects. Asthmatics are the primary victims of such indoor particulate pollution, due to oversensitivity of the immune system to otherwise harmless particles such as pollen.
PM10 pollution can be highly dependent on weather patterns, with high concentration occurring on warmer, less windy days. This prevents the particulate matter from being dispersed, and particulate pollution can build up near busy roads. The concentration of particulate is expected to decrease somewhat in the next ten years, as EU regulations for vehicle emissions come into force. However, the overall levels of particulate pollution are difficult to predict, as wind patterns may blow PM10 pollution from Eastern Europe into the country.
Particulate matter in the home can be generated through many types of improperly ventilated household appliances.
Due to the dangerous nature of PM10s, warning homeowners of excessively large concentrations would be extremely valuable. Unfortunately, the size and cost of the sensors along with the complex nature of the sampling methods mean that the service is not viable.
However, PM10s released by living organisms can be monitored indirectly by a humidity sensor, with the central assumption that moisture is the limiting factor for the production of these pollutants. (see Mould/Dustmite service)

Radon Gas

Radon gas occurs naturally by the radioactive decay of Uranium, which is present in small quantities underneath houses and in some building materials. The gas, like Carbon Monoxide, is colourless, odourless and tasteless but has been identified as the second largest cause of lung cancer after smoking. Radon levels vary widely in the UK, but the gas is particularly prevalent in areas of granite or limestone. Especially where these rocks make up the building materials, for example, in "the Granite City" of Aberdeen.
Concentrations in the open air are very low. Radon in soil and rocks mixes with air and rises to the surface where it is quickly diluted in the atmosphere. However, Radon that enters enclosed spaces and buildings, can reach relatively high concentrations in some circumstances, especially in buildings with insufficient ventilation.
Health Effects of Radon Inhalation.
Breathing high concentrations of radon can cause lung cancer. The risk is nevertheless small because the gas is radiologically not very active, with a half-life of 4 days. Unfortunately, the decay products of radon itself are more hazardous isotopes of solid elements with an active 30 minute half-life. These particles, such as Polonium, irradiate the lungs more effectively upon inhalation and are especially dangerous since they can attach to other natural aerosols and subsequently become lodged in the lining of the respiratory system. It is therefore important to reduce indoor radon concentrations as low as reasonably practicable. In the UK, half of the average human radiation exposure is attributable to Radon
In addition, smoking and exposure to radon are known to work together to greatly increase the risk of developing lung cancer. Smokers may be several times more likely to contract lung cancer from a lifetime radon exposure at 200Bqm-3 than the general population (SOURCE: the 6th Committee of the Biological Effects of Ionising Radiation of the American National Academy of Science).
It is believed that environmental radon accounts for between 2000 and 3,300 lung cancer deaths in the UK annually, which is 3 - 5% of the total lung cancer deaths.

Radon Detection

Radon levels in homes vary on both a daily and yearly basis. This is mainly because of temperature differences between indoors and outdoors. Concentrations of Radon are generally higher at night and during the winter. Even in a home with good draught proofing and double-glazing, the air changes several times a day. Increasing the ventilation, especially on the ground floor, will in most cases cause a moderate reduction in the radon level.

There are four main categories of detectors: -

Etched-track detectors - The most popular and cost effective detector. Alpha particles leave tracks in a plastic over a three-month period. The detectors are sent to labs, processed to reveal the pitting made by alpha particles. The pits are microscopically counted permitting a radon level to be computed.

Electret detectors - These can be used for measurements over periods from days to months; operates by gauging the loss of electrostatic charge which is neutralised by alpha particles emitted by radon and its decay products over the period, from which radon concentration can be calculated. These detectors are extremely delicate and must be handled carefully for accurate results.

Charcoal detectors - Not suitable for long-term measurement; least accurate and used when a rapid measure is required. Activated charcoal absorbs radon, and the laboratory can determine a rough estimate of radon concentration.

Active monitors - The most effective and expensive Radon detector. Provides an electronic continuous measure of radon or its decay products; permits figures to be obtained over consecutive hours.

The viability of measuring Radon levels in homes.

As discussed above, the presence of Radon gas in homes causes considerable adverse health effect on home occupants. Monitoring of Radon Gas levels could in theory, prevent about 5% of lung cancer deaths. However, the existing sensors cannot be used for continuous measurement and the cost of implementation would be high. One measurement is also likely to be more effective, since Radon is a naturally occurring gas whose production cannot be prevented. The adverse health effects occur over a long period of time and the concentrations do not tend to fluctuate. There is therefore no need for a system with a dynamic response to concentration changes. Additionally, a single remedial measure can remove the health risk, for example improving ventilation or fitting an airtight membrane underneath carpets.

NOx

Nitrogen Oxide and Nitrogen Dioxide, commonly referred to as NOx, are widely regarded to cause health problems and Environmental Impact upon release into the environment. NO is more readily emitted to the atmosphere as a primary pollutant, from traffic and power stations, and is often oxidised to the more toxic nitrogen dioxide following dispersal. Road Vehicles are responsible for over 50% of the emissions of nitrogen oxides in the UK. Annual mean concentrations of NO2 in urban areas are generally in the range 10-45ppb. Levels vary significantly throughout the day, with peaks generally occurring twice daily as a consequence of "rush hour" traffic. Since Nitrogen Dioxide can be formed in the home by gas appliances, fireplaces, and poorly maintained wood or coal stoves, it should be considered along with other indoor air pollutants.

Formation of NOx

Three reaction paths, each with unique characteristics, are responsible for the formation of NOx: Thermal NOx is formed during high temperature processes that result in the combination of atmospheric Nitrogen and Oxygen.
Fuel NOx is formed through the oxidation of fuel-bound Nitrogen in motor vehicles, electric utilities, and other industrial, commercial, and residential sources that burn fuels.
Prompt NOx is formed by the reaction of fuel derived hydrocarbon fragments with atmospheric Nitrogen.
It is also worth noting that denitrificating bacteria form Oxides of Nitrogen as part of the natural nitrogen cycle.

Health and Environmental Problems Associated with NOx
Ground level Ozone or smog is formed when NOx and volatile organic compounds react in the presence of heat and sunlight. Children, asthmatics, and people who work or exercise outside are susceptible to adverse effects such as damage to lung tissue and reduction in lung function. The pollutant is also suspected to have carcinogenic and mutagenic properties. In addition visibility in cities can be impaired, and a unsightly red-brown haze may be observed at dusk.
NOx and sulphur dioxide can react with other substances in the air to form acid rain which can cause deterioration of cars, buildings and historical monuments; and cause lakes and streams to become acidic and unsuitable for numerous species of aquatic life.
NOx reacts with ammonia, moisture, and other compounds to form nitric acid and related particles. Human health concerns include effects on breathing and the respiratory system, and damage to lung tissue. Small particles penetrate deeply into sensitive parts of the lungs and can cause chronic respiratory disease such as emphysema and bronchitis, also aggravate existing heart disease.
Water Quality Deterioration can be caused by increased nitrogen loading in receiving waters, particularly coastal estuaries. Additional nitrogen may contain a considerable BOD load, causing nitroficating micro-organisms to thrive, accelerating "eutrophication," and "algal bloom" which leads to oxygen depletion and reduces fish populations.
Nitrous oxide is a greenhouse gas, which accumulates in the upper atmosphere. Scientists believe the pollutant contributes to the "Greenhouse Effect".

The viability of monitoring NOx in the home.

Although NOx is a problem for outdoor air quality, causing smog over cities and contributing to acid rain, it is nevertheless far less dangerous to humans than PM10s and other outdoor air pollutants. To date NOx emissions have not been linked to excessive mortality. It can be concluded that this health effect is further reduced in the home environment, separate from industry and traffic.
Although it can be formed in the home, it is largely produced outside and has not presented a significant health problem for home and building occupants.
Additionally the sensors are large and expensive making an information service based on the health effects of NOx not viable.