English Abstract This report describes the results of
polychlorodibenzo-p-dioxins (PCDDs) and furans (PCDFs) measurements in
ambient air in a rural area in the centre of the city conglomerate
'Randstad", about 30 km North of a large industrial area 'Botleck' and two
large capacity refuse waste incinerators (Rotterdam and AVR). Measurements
were performed near the village of Zegveld during the period of June and
July 1993. Dioxin concentrations found varied between 5+-2 to 60+-15 fg
TEQ/m3, depending on the wind direction and other weather conditions with an
average value of 18+-18 fg TEQ/m3 (n=11). The high range levels were found
in trajectories from the South-West, down stream from the incinerators, and
relatively low levels (<5-10 fg TEQ/m3) in trajectories from West (North
Sea), North and East. The long-term-average background level was calculated
as 25+-5 fg TEQ/m3 based on estimates of mean concentrations in the four
trajectory directions, weighed with the corresponding long-term-average
distribution of wind directions. This background value corresponds fairly
well with a predicted value of 35 fg/m3. Model calculations were based on
the estimated national emissions and dioxin fluxes from abroad by the end of
1990. When results from both methods are mutually comparable and valid, the
small difference might indicate a small, poorly significant dicline of
dioxin levels in air in this part of the country during the past few
years.