2.—(1) The Schedule to the Air Quality (Wales) Regulations 2000(1) is amended as follows.
(2) In the Table in Part I of the Schedule—
(a)create an additional row which relates to benzene, and—
(i)in the column headed “Substance/Air quality objective levels” insert “Benzene: 5 micrograms per cubic metre or less, when expressed as an annual mean”;
(ii)in the column headed “Date by which objective to be achieved” insert “31 December 2010”; and
(b)in the row which relates to carbon monoxide and the column headed “Substance/Air quality objective levels”, substitute “10” for “11.6” and insert “maximum daily” before “running 8 hour mean”.
(3) In Part II (Interpretation) of the Schedule—
(a)for paragraph 2 (which relates to the calculation of a running 8 hour mean) substitute—
“2.—(1) A maximum daily running 8 hour mean is calculated on a daily basis. The maximum daily running 8 hour mean for a particular substance at a particular location for a particular day is the maximum of the running 8 hour means ending during that day.
(2) For the purpose of sub-paragraph (1), a “running 8 hour mean” is a mean which is calculated on an hourly basis, yielding one running 8 hour mean per hour. The running 8 hour mean for the relevant substance at the relevant location for a particular hour is the mean of the hourly means for the substance at the location for that hour and the preceding 7 hours.”
(b)in paragraph 3 (which relates to the calculation of an annual mean in the case of lead etc.)—
(i)delete “and” in sub-paragraph (1)(b);
(ii)after “year” in sub-paragraph (1)(c) insert—
“; and
in the case of benzene, either the mean of the daily levels for that year or the mean of the hourly means for that year”; and
(iii)for sub-paragraph (4) substitute—
“(4) For the purpose of any calculation of the annual mean for benzene on the basis of the mean of the daily levels, the daily level for benzene at a particular location for a particular day is the level at which benzene is recorded as being present in the air at that location during the fortnight in which the day occurs on the basis of a continuous sample of air taken throughout that fortnight (each day in the fortnight therefore being attributed with the same daily level).”
(c)in paragraph 4 (which relates to the calculation of an hourly mean), for the second sentence substitute—
“The hourly mean for a particular substance at a particular location for a particular hour is the mean of the levels recorded for that substance at that location:
in the case of benzene, at a frequency of not less than once during the hour; and
in the case of carbon monoxide, nitrogen dioxide and sulphur dioxide, at a frequency of not less than once every 10 seconds during the hour.”