Encyclopedia of Environmental Science and Engineering, Volume I and II

PCBs AND ASSOCIATED AROMATICS 873

48% by weight chlorine substituted biphenyl. The fluid was

used by the rice oil manufacturer as a fire hazard reduction

measure in an indoor heat exchanger.

The PCB concentration in Yusho oil was found to be

about 1000 ppm PCB (Kuratsune et al.^4 ). As analytical

capabilities increased there has been a parallel increase

in the speculation that the causative agents found in the

rice oil such as polychlorinated dibenzofurans (PCDFs)

and polychlorinated quaterphenyls (PCQs) (Masuda and

Yoshimura^5 ) had much greater relative toxicities. Original

estimates of the PCB contamination were in the range

of2000–3000 ppm PCB but were found to be in error

primarily because of the analytical interference presented

by PCQs.

TABLE 13

PCB products manufactured in the United States fortunately have low concentrations of PCDF impurities

Commercial

Product

Chlorinated Dibenzofurans

Di- Tri- Tetra- Penta- Hexa- Hepta- Total

(1) 1016 ND ND <0.001 <0.001 — <0.001 —

(1) 1248 ” ” 0.5 1.2 0.3 — 2.0

(1) 1254 ” ” 0.1 0.2 1.4 — 1.7

(1) 1254 ” ” 0.2 0.4 0.9 — 1.5

(1) 1260 ” ” 0.1 0.4 0.5 — 1.00.8

(1) 1260 ” ” 0.2 0.3 0.3 — 8.4

(2) A-60 ” ” 1.4 5.0 2.2 — 13.6

(3) DP-6 ” ” 0.7 10.0 2.9 — 17–18

(4) K-400 ” ” — — — — —

(1) Aroclor; (2) Clophen; (3) Phenoclor; (4) kanechlor. Data from Bowes et al.^2 and Nagayama et al.^3

FIGURE 15 Structural categories of PCBs.

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