- Acid Deposition
Total atmospheric deposition of acidity is determined using both wet and dry deposition measurements. Wet deposition is the portion dissolved in cloud droplets and is deposited during rain or other forms of precipitation. Dry deposition is the portion deposited on dry surfaces during periods of no precipitation as particles or in a gaseous form. Although the term "acid rain" is widely recognized, the dry deposition portion ranges from 20 to 60 percent of total deposition.
- Acid Rain
When atmospheric pollutants such as sulphur dioxide and nitrogen oxides mix with water vapour in the air, they are converted to sulphuric and nitric acids. These acids make the rain acidic, hence the term 'acid rain'. Acid ran is defined as any rainfall that has an acidity level beyond what is expected in non-polluted rainfall. Acidity is measured using a pH scale, with the number 7 being neutral. Consequently, a substance with a pH value of less than 7 is acidic, while one of a value greater than 7 is basic. Generally, the pH of 5.6 has been used as the baseline in identifying acid rain. Thus any precipitation that has a pH value of less than 5.6 is considered to be acid precipitation.
- Air Pollution Bandings
The Air Pollution Information Service uses four bands to describe levels of pollution. The bands are low, moderate, high and very high. Healthy people do not normally notice any effects from air pollution, except occasionally when air pollution is "very high".
- Air Pollution Bulletins
Air Pollution Bulletins are issued daily for each zone of the UK. The bulletins show current air quality, and a forecast for the next 24 hours, classified into four bands and also into an index.
- Air Pollution Index
A numerical index for air pollution from 1 to 10 related to the air quality bands of "low", "moderate", "high" or "very high".
- Air Pollution Information Service
The Air Pollution Information Service provides - free of charge - detailed, easy-to-understand information on air pollution. This information is particularly important to people with medical conditions which air pollution may make worse. The latest information is available by freephone, on Ceefax and Teletext, and via the Internet. The Service gives regionally based summaries and detailed information on current pollution levels, as well as forecasts for the next 24 hours.
- Air Quality Management Area (AQMA)
If a local authority finds any places where the objectives are not likely to be achieved, it must declare an Air Quality Management Area there. This area could be just one or two streets, or it could be much bigger. Then the local authority will put together a plan to improve the air quality - a Local Air Quality Action Plan
- Air Quality Objectives
Objectives are policy targets generally expressed as a maximum ambient concentration to be achieved, either without exception or with a permitted number of exceedences, within a specified timescale.
- Air Quality Standards
Standards are the concentrations of pollutants in the atmosphere which can broadly be taken to achieve a certain level of environmental quality. The standards are based on assessment of the effects of each pollutant on human health including the effects on sensitive sub-groups.
- Air Quality Strategy
The Air Quality Strategy for England, Scotland, Wales and Northern Ireland describes the plans drawn up by the Government and the devolved administrations to improve and protect ambient air quality in the UK in the medium-term. The Strategy sets objectives for the main air pollutants to protect health. Performance against these objectives will be monitored where people are regularly present and might be exposed to air pollution.
- Ambient Air
The air occurring at a particular time and place outside of structures. Often used interchangeably with "outdoor air".
- Annual Mean
The average of the concentrations measured for each pollutant for one year. Usually this for a calendar year, but some species are reported for the period April to March, known as a pollution year. This period avoids splitting a winter season between two years, which is useful for pollutants that have higher concentrations during the winter months.
- Automatic Monitoring
Monitoring is usually termed "automatic" or "continuous" if it produces real-time measurements of pollutant concentrations. Automatic fixed point monitoring methods exist for a variety of different pollutants and these can provide high resolution data averaged over very short time periods.
- EMEP (Co-operative Programme for Monitoring and Evaluation of the Long-Range Transmission of Air pollutants in Europe)
The EMEP programme consists on three main elements: (1) collection of emission data, (2) measurements of air and precipitation quality and (3) modelling of atmospheric transport and deposition of air pollution. EMEP regularly reports on emissions, concentrations and/or depositions of air pollutants, the quantity and significance of transboundary fluxes and related exceedences to critical loads and threshold levels. The EMEP programme is carried out in collaboration with a broad network of scientists and national experts that contribute to the systematic collection, analysis and reporting of emission data, measurement data and integrated assessment results.
- Emission Factor
The relationship between the amount of pollution produced and the amount of raw material processed or burned. For mobile sources, the relationship between the amount of pollution produced and the number of vehicle miles travelled. By using the emission factor of a pollutant and specific data regarding quantities of materials used by a given source, it is possible to compute emissions for the source. This approach is used in preparing an emissions inventory.
- Emission Inventories
Emission inventories are estimates of the amount and the type of pollutants that are emitted to the air each year from all sources. There are many sources of air pollution, including traffic, household heating, agriculture and industrial processes.
The Expert Panel on Air Quality Standards was set up in 1991 to provide independent advice on air quality issues, in particular the levels of pollution at which no or minimal health effects are likely to occur. Members of the Panel are primarily drawn from those eminent in the fields of health research, practice and teaching. The Panel's recommendations were adopted as the benchmark standards in the National Air Quality Strategy.
- EU Directives
The European Union has been legislating to control emissions of air pollutants and to establish air quality objectives for the last two decades. After many years of a somewhat piece-meal approach, ambient air quality legislation is now being consolidated. Directive 96/62/EC on ambient air quality assessment and management, the so called Air Quality Framework Directive, sets a strategic framework for tackling air quality consistently by setting European-wide limit values for twelve air pollutants in a series of daughter directives. These will supersede and extend existing European legislation.
A period of time where the concentration of a pollutant is greater than, or equal to, the appropriate air quality criteria. For air quality standards an exceedence is a concentration greater than the standard value. For air quality bands an exceedence is a concentration greater than, or equal to, the upper band threshold.
Polycyclic Aromatic Hydrocarbons (PAHs) belong to a large group of organic compounds ; several individual PAHs have been shown to be carcinogenic. EPAQS have recommended a standard for PAHs of 0.25 ng/m3 using benzo[a]pyrene as a marker compound.
- Particulate matter (PM10)
Particulate matter consists of very small liquid and solid particles floating in the air. Of greatest concern to public health are the particles small enough to be inhaled into the deepest parts of the lung. These particles are less than 10 microns in diameter - about 1/7th the thickness of the a human hair - and are known as PM10 .Concern about the potential health impacts of PM10 has increased very rapidly over recent years. Increasingly, attention has been turning towards monitoring of the smaller particle fraction (PM2.5) capable of penetrating deepest into the lungs, or even to total particle numbers.
A value that is the rank at a particular point in a collection of data. For instance, a 98th percentile of values for a year is the value that 98% of all the data in the year fall below, or equal.
Persistent Organic Pollutants (POPs) are chemical substances that persist in the environment, bioaccumulate through the food web, and pose a risk of causing adverse effects to human health and the environment. These include dioxins and furans (see TOMPS)
Parts per billion. The concentration of a pollutant in air in terms of volume ratio. A concentration of 1 ppb means that for every billion (109) units of air, there is one unit of pollutant present.
Parts per million. The concentration of a pollutant in air in terms of volume ratio. A concentration of 1 ppm means that for every million (106) units of air, there is one unit of pollutant present.