For phenol a threshold for odour perception in air of 184 µg/m3 and a threshold for taste andodour in water of 150 µg/l has been reported (Verschueren 1996).Chlorophenols generally have very low organoleptic thresholds. The taste threshold in water for2-chlorophenol, 2,4-dochlorophenol and 2,4,6,-trichlorophenol are 0.1, 0.3 and 2 µg/l (WHO,1996).From these values it can be concluded that phenol in drinking water will normally not give raiseto taste and odour problems. But, drinking water containing only a few µg/l of phenol may be EU RISK ASSESSMENT – PHENOL SUMMARY, NOVEMBER 20066unacceptable after chlorination due to the low threshold values for chlorophenols. Therefore, theFederal Environmental Agency of Germany recommends an aesthetic guide value (ästhetischerLeitwert) of 1 µg phenol per litre of drinking water in order to guarantee the option to chlorinatewater if necessary without deteriorating its aesthetic quality with respect to taste and odour.