# The Environmental Targets (Fine Particulate Matter) (England) Regulations 2022, Paragraph 3: Calculation of PEIbase, Population Exposure Indicator and Reference Indicator


(1) PEIbase is to be calculated by carrying out the following steps—
step 1: the mean is calculated of the annual mean PM2.5 level in 2016 for each baseline monitoring station which was in operation throughout that year and met the minimum annual data capture requirement in that year;
step 2: step 1 is repeated for 2017 and 2018;
step 3: the mean of the values calculated under steps 1 and 2 for the years 2016, 2017 and 2018 is calculated to obtain PEIbase.
(2) The Population Exposure Indicator for a year (“PEIyear”)is to be calculated by carrying out the following steps—
step 1: the mean is calculated of the annual mean PM2.5 levels in that year for each PEI monitoring station, excluding any PEI monitoring station which did not meet the minimum annual data capture requirement in that year;
step 2: step 1 is repeated for each of the two preceding years;
step 3: the mean of the values calculated under steps 1 and 2 for those three years is calculated to obtain PEIyear.
(3) The Reference Indicator for a year (“RIyear”)is to be calculated by carrying out the following steps—
step 1: the mean is calculated of the annual mean PM2.5 levels in the preceding year for each PEI monitoring station, excluding any PEI monitoring station which did not meet the minimum annual data capture requirement in that year;
step 2: step 1 is repeated for each of the two previous years;
step 3: the mean of the values calculated under steps 1 and 2 for those three years is calculated to obtain RIyear.

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Source: https://www.legislation.gov.uk/ukdsi/2022/9780348242959/schedule/1/paragraph/3 (the official version)
Page: https://openlegislation.uk/draft-environmental-targets-fine-particulate-matter-england-regulations-2022/schedule-1/paragraph-3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.