# The Air Quality Standards Regulations 2010, Regulation 2: Definitions

Extent: E+W+S+N.I.

In these Regulations—
“ambient air” means outdoor air in the troposphere, excluding workplaces where members of the public do not have regular access;
“AOT 40” (expressed in (μg/m3)∙ hours) means the sum of the difference between hourly concentrations greater than 80 μg/m3 (=40 parts per billion) and 80 μg/m3 over a given period using only the one-hour values measured between 08.00 hours and 20.00 hours Central European Time (CET) each day;
“arsenic”, “cadmium”, “nickel” and “benzo(a)pyrene” mean the total content of those elements and compounds within the PM10 present in ambient air;
“Directive 2008/50/EC” means Directive 2008/50/EC of the European Parliament and of the Council on ambient air quality and cleaner air for Europe;
“Directive 2004/107/EC” means Directive 2004/107/EC of the European Parliament and of the Council relating to arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air;
“fixed measurements” means measurements taken at fixed locations, either continuously or by sampling from time to time, to determine levels of pollutants in accordance with the relevant data quality objectives;
“indicative measurement” means measurements which meet data quality objectives that are less strict than those required for fixed measurements;
“margin of tolerance” means the percentage of the limit value by which that value may be exceeded in a given year;
“oxides of nitrogen” means the sum of the volume mixing ratio (ppbv) of nitrogen monoxide (nitric oxide) and nitrogen dioxide expressed in units of mass concentration of nitrogen dioxide (μg/m3);
“ozone precursor substances” means substances which contribute to the formation of ground level ozone;
“PM10” means particulate matter which passes through a size-selective inlet as defined in the reference method for the sampling and measurement of PM10, EN 12341, with a 50% efficiency cut-off at 10 μm aerodynamic diameter;
“PM2.5” means particulate matter which passes through a size-selective inlet as defined in the reference method for the sampling and measurement of PM2.5, EN 14907, with a 50% efficiency cut-off at 2.5μm aerodynamic diameter;
“particulate matter” means PM2.5 and PM10;
“pollutant” means any of the following—
(a)sulphur dioxide,
(b)nitrogen dioxide,
(c)oxides of nitrogen,
(d)particulate matter,
(e)lead,
(f)benzene,
(g)carbon monoxide,
(h)arsenic,
(i)cadmium,
(j)mercury,
(k)nickel,
(l)benzo(a)pyrene or other polycyclic aromatic hydrocarbons,
(m)ozone;
“polycyclic aromatic hydrocarbons” means those organic compounds composed of at least two fused aromatic rings made entirely from carbon and hydrogen;
“relevant administration” means—
(a)the Welsh Ministers for Wales;
(b)the Scottish Ministers for Scotland; and
(c)the Department of the Environment for Northern Ireland;

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Source: https://www.legislation.gov.uk/uksi/2010/1001/regulation/2 (the official version)
Page: https://openlegislation.uk/air-quality-standards-regulations-2010/regulation-2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.