The role of chlorinated phenols as dioxins precursors in the bleach pl
ant, was investigated. It was shown that these compounds are not signi
ficant in the formation of dioxins. Rather, the weight of evidence sug
gests that the precursors of the tetrachlorinated dioxins and furans g
enerated in bleach plants are their corresponding unchlorinated analog
ues, dibenzo-p-dioxin and dibenzofuran.