There are no known natural sources of 1,2-DCB, 1,4-DCB, TCBs, TeCBs or QCB. 1,2-DCB and 1,4-DCB are the only CBzs under examination that are produced in Canada (Table 1). ###>Il n’existe pas de sources naturelles connues de 1,2-DCB, de 1,4-DCB, de TCB, de TeCB ou de QCB.