Document jZ2r6EGam7Ywab2z8VpgogZQ

77-76 SCIENCE TEACHER Ha. 23,000 JUN 1975 (SI not The Effects of Polychlorinated Biphenyls (PCBs) on Chick Embryos BERNARD McTADDEN Mr. Mcfsdtfsn It sclsnct chairman at W. I. Clark* High School, Wsstfcury, N*w York. Tha raaaarch and axparlmanta for thla pro|*ct war* carrtaC oat by Mltchall StMn, * aophomor* at tha Within tha last few yaara, polychlorinated biphanvla (PCBs) have been identified aa chemical pollutant*, harmful to birds, fish, and mammals. PCBs an or* ganic chlorine compounds chemically similar to DDT. They are uaed in the electrical industry as insulators, in the hydreulice industry for high temperature lubri cants, and in die plastics and paint industrias for their plasticising properties. When PCBa ere present in the food chain and the compound is ingested, the chem icals become concentrated in the fatty tissue of ani mals. If the accumulation of PCBa becomes great enough, it can be lethal to eoraa fish and aquatic invertebrates. Recently, deformities in tern chicks were noted on Greet Gull Island in Long Island Sound where s high concentration of PCBa exists. A student et W. T. Clarke High School decided to add to the data ac cumulated on PCBs by testing their effects on white leghorn chicken eggs. He hypothesised that the ef fects of PCBs on the Long Island tern chicks could be duplicated in the laboratory by injecting PCBa into fertile chick eggs. He also hypothesised that the fa tality rate and degree of malformation in the chick embryo would be function of the percent of chlorine content in the PCBs. Three different types of PCBa (Arodor 1221, 1242, and 1254) were obtained from the manufacturer. The last two digits of the identification number indicate the weight percentage of chlorine in the product. Thus, Aroclor 1221 hss 21 percent chlorine, 1242 has 42 percent, end 1254 hss 54 percent Forty-eight freshly fertilised white leghorn chicken eggs were purchased. Hole* were drilled in the egg shells with s dental drill. A hypodermic syringe was used to inject the solution into the eggs. Sterile pro cedures were observed at sll times. Com oil was used to dilute the PCBs because it is nontoxic end PCBs iro soluble in it. The student measured out 200 mg, 300 mg, and 400 mg of each Aroclor PCB and added these quantitias, respectively, to vials containing 10 cc of com oil. Thus, concentra tions of 10 mg, 15 mg, and 20 mg par 4 cc were achieved. Nine solutions were prepared and admilet tered to 39 chick eggs. The remaining nine eggs were used as controls. After 17 days of incubation, the eggs were opensd and the embryos detached from the smrootk sere. Rnch embryo was examined end preserved. The re sults of the experiment indicate that PCBs with chlo rine levels at 42 percent or greeter, in doses larger than 10 mg/0.6 cc, are fatal to chick embryos. PCBs with a 21 percent chlorine content, in doses of 10 mg/0.5 cc, result in smaller embryos than normal, with sise decreasing as the dosage is increased. Mal formation of the embryo also appear* with larger dosre. PCBs represent examples of chemicals introduced by industry to satisfy a technical need that have now been discovered to be major pollutants of the environ ment. The experiments performed by tha student on chick embryos indicate that PCBs have a detrimental effect on the poeeibilitiee for eurvival of certain specie* of aquatic predatory birds. a fRight) Mitchell infecting chick atl *Rh PCS solution. (Bate*) Explaining rssufti to a fellow student. JUNE 1075 HONS 031079 is