§ Mr. Pardoe
asked the Secretary of State for Education and Science what were the maximum, average and minimum levels of mercury found in samples of seawater taken from British coastal waters in 1970; how many samples were tested; and from how many different areas they were taken.
§ Mrs. Thatcher
Measurements of the inorganic mercury content of seawater in the English Channel were made at three locations during the period May to December, 1970. Four sets of measurements were taken, five or six samples being taken on each occasion. The average concentration of mercury present in each group of samples ranged from 0.014 to 0.021 microgramme per litre of seawater. The average concentration in the 299W samples as a whole was 0.019 microgramme per litre. The number of samples totalled 22.