News of the Week acre, harvested on a rotating basis every two to six years. The Navy is committed to buying 275,000 lb of the rubber. If Firestone technology makes guayule rubber competitive with conventional natural rubber from Hevea plants in Southeast Asia, the Navy may buy additional amounts to keep the fledgling industry going. About 6 lb of groundup, defoliated guayule shrub yields 1 lb of rubber, 12 oz of resin (terpenes and triglycerides), and 4.5 lb of bagasse. Firestone will evaluate water flotation and solvent extraction methods to isolate the rubber. The company estimates that that amount of bagasse as fuel contains an excess of 1500 Btu of heat above and beyond what is needed to grow, process, and recover the 1 lb of rubber. D
PCB levels in humans decline sharply A nationwide survey of polychlorinated biphenyl levels in human fat tissue shows a sharp decline in recent years. The latest figures for 1981 show that just 1% of the U.S. population has concentrations of PCBs greater than 3 ppm, a decrease from more than 8% of the population in the peak year 1977. On the other hand, the stubborn persistence of PCBs in the environment leads to the finding that virtually everyone has some measurable tissue levels of these compounds. The decline in body levels of PCBs "is a dramatic example of the imp r o v e m e n t s that e n v i r o n m e n t a l regulations are bringing us," says Donald R. Clay, acting assistant administrator for pesticides and toxic substances at the Environmental Protection Agency. EPA attributes the drop to the fact that PCBs were destroyed or stored where people will not be exposed to them after the 1976 Toxic Substances Control Act banned production or new use of PCBs. The chemical industry stopped producing the compounds voluntarily in 1974. The study was done by the National Adipose Tissue Survey, which began in 1972 and has analyzed 800 8
May 16, 1983 C&EN
to 1800 tissue samples yearly to determine the levels of about 20 lipidsoluble contaminants in humans. The samples are submitted by cooperating physicians and pathologists from surgery patients and cadavers. Other chemicals analyzed for include DDT, aldrin, dieldrin, heptachlor, chlordane, and hexachlorobenzene. The 3-ppm level of PCBs chosen as a reference level in the survey has no health significance, an EPA spokesman told a press conference
when the data were released. It's a point readily identified in the analytical method used, as are the other ranges measured: from 1 to 3 ppm, less than 1 ppm but detectable, and undetectable. There are no data to show that 3 ppm of PCBs can cause any adverse health effects in humans. It's curious that EPA waited until now to announce the survey's good news. The technical report on the survey, from Research Triangle Institute, is dated Nov. 12, 1982. D
Chemical analysis foils Hitler diaries hoax Knowledge of chemistry coupled with analytical skills makes it all but impossible for a forger to get away with a crime. The unmasking of the bogus diaries of Adolf Hitler is recent and dramatic evidence of how science and technology come to the aid of law and order. The diaries, purportedly penned by Hitler between 1932 and 1945 when he led the German Third Reich, were bought by the publisher of Stem, a leading West German weekly magazine, for about $4 million. Their origin is obscure, although they supposedly were found in a barn in East Germany. They appeared so convincing that they
Stern magazine reporter Gerd Heidemann holds up books the magazine believed to be Hitler's diaries
fooled some of the intelligentsia of modern history studies for a while. But the books were unmasked as forgeries by some skillful chemical detective work led by Louis-Ferdinand Werner at the West German Federal Criminal Office, the country's national forensic laboratories, in Wiesbaden. He and his group subjected three of the 64 volumes to a series of tests that "clearly established that the diaries are obvious fakes," Werner says. Though he is constrained from going into details about the studies until he formally submits his official report, he has revealed some of the salient points of the findings to C&EN. The first clue came from observing the degree of "whiteness" of the paper under ultraviolet light. Samples were dissolved, and the solution subjected to thin-layer chromatography. One of the components they always found was a derivative of stilbene. Its use as an optical brightener in the manufacture of white paper did not begin until the mid-1950s. This in itself would appear to be sufficiently damning evidence against the validity of the diaries. But Werner and his group didn't stop there. Infrared spectroscopic analysis of glue in the bindings revealed the presence of polyvinyl pyrrolidone, a post-World War II component of adhesives. They also established the presence of nylon 6 fibers. "These weren't used in [binding] books prior to 1955," Werner remarks. Results of the analysis of the ink were not available at press time. D
