The Impact of Pesticides - Academy Publish

In 1998 around 45% of the 389 sites at which monitoring took place showed noMPC exceedance. In 2009 that percentage was approximately the same: 46%. Thisconclusion holds broadly for all the intervening years: over the years the percentageof ‘clean’ locations where there was absolutely no exceedance of the MTR standardhas remained roughly the same. Similarly, the percentage of sites withmeasurements exceeding the MPC has also remained essentially unchanged over theyears. At the same time, though, between 1998 and 2009 the number of monitoringsites rose by around 60%: from 447 in 1998 to 713 in 2009.Seasonal variation of compoundsWater boards and other ‘competent authorities’ monitor the chemical quality ofwatercourses all the year round. Crops have a sow-grow-harvest cycle, during thevarious phases of which pesticide use is bound to vary, and the pesticide levelsmonitored at any given site correlate very much with the particular activities takingplace on adjacent plots. Over the years approximately the same number ofcompounds are monitored each month. Nationwide, in 2009 the number varied fromjust over 300 to around 600.Figure 3: Number of pesticides recorded monthly in 2009 (above) and percentage ofcompounds exceeding the MTR in each month of that year (below). J = January, F= February, M = March, etc.AcademyPublish.org - The Impact of Pesticides195