|
SCIENCE INSIGHTS |
|
The alleged presence of a chemical warfare agent precursor in a soil sample obtained near a Sudanese pharmaceutical plant served as justification for a U.S. cruise missile attack on the plant last August. Coming just after President Bill Clinton's nationally televised admission of an affair with a White House intern, it was tempting to suspect that the attack was launched to divert attention from the scandal. No details were released to support the U.S. claim that the El Shifa Pharmaceutical Industries plant in Khartoum was producing O-ethylmethylphosphonothioic acid (EMPTA), a precursor to the nerve gas VX. U.S. officials said, and continue to say, only that they have physical evidence in the form of a soil sample that analysis revealed to contain EMPTA. Supposedly the sample was collected two months before the attack but analyzed one month after collection. See Figure. Little other information was offered. The government would have us believe that details would compromise intelligence activities. Perhaps revealing how the sample was collected might pose risks. But how could intelligence activities be jeopardized by disclosing the amount found, the analytical techniques used, or the other chemicals detected? In September, the pharmaceutical plant's owner, Salah Idris, commissioned a study of samples from the facility's remains to bolster his and the Sudanese government's vehement denials that EMPTA was being produced or used in the plant. The study was designed and directed by Thomas D. Tullius, chairman of the chemistry department at Boston University, and executed by three European laboratories and the international engineering firm Dames & Moore, Manchester, England (C&EN, Feb. 15, page 11). Tullius' recent discussion of the study with C&EN is a refreshing change from the "we can't say anything about that" line from U.S. officials. He provided the name of the person who collected and handled the samples. He said when, where, and how the samples were taken, preserved, and transported. He talked about analytical techniques, protocols to ensure the quality of results, and limits of detection. And he is ready to name the labs that did the analyses, but refrains from doing so on the advice of Idris' lawyers. The European labs analyzed the samples for EMPTA, its immediate breakdown product EMPA (O-ethylmethylphosphonic acid), and 25 organophosphorus pesticides. The bulk of the work on EMPTA and EMPA was done by a lab Tullius describes as one of the few certified by the Organization for the Prohibition of Chemical Weapons to do chemical analyses related to the Chemical Weapons Convention. According to Tullius, this lab carried out R&D work to establish the optimum parameters for detecting EMPTA, including spiking experiments to determine its persistence. "We found in actual Sudan soil samples that even after one day a considerable amount of EMPTA is broken down and that after five days less than 2% of the spiked EMPTA can be recovered," Tullius says. Given the instability of EMPTA in soil, how believable is the U.S. government's claim of finding EMPTA in a soil sample analyzed one month after it was collected? Furthermore, everything in the literature suggests that the hydrolysis product, EMPA, should be much more difficult to break down than EMPTA, Tullius says. And it likely can last for years, he adds. Indirect evidence for EMPA's persistence comes from analysis of the chemical warfare agent sarin and its degradation product in samples collected from a Kurdish village in northern Iraq four years after the village was attacked with chemical agents [J. Chromatogr. A,662, 301 (1994)]. Sarin rapidly hydrolyzes to O-isopropyl methylphosphonic acid (iPMPA). The study of the Kurdish samples, by scientists at the Chemical & Biological Defense Establishment, Porton Down, England, found iPMPA in soil samples at levels ranging from 6 to 200 ppb. After four years, a compound very similar to EMPA still was detectable. It's reasonable to assume that EMPA will behave similarly. Wouldn't analysis of the sample of Sudanese soil that allegedly contains EMPTA also be likely to reveal the presence of the more stable degradation product EMPA? U.S. officials mention only a finding of EMPTA. Perhaps they also found EMPA but aren't telling. Of all the samples obtained at the pharmaceutical plant site for the study commissioned by the plant's owner, none turned up with any EMPTA or EMPA. A spokesman for the National Security Council says: "It's not surprising that claims by scientists and investigators working for Salah Idris would conclude that the plant was not linked to chemical weapons." And although unsure whether the agency actually has a copy of the study's findings, he goes on to say, "The compounds, EMPTA or EMPA, would only be detectable for weeks or a month, and their investigation took place two months after the attack. During that time, heavy rains, the fire at the plant, the water used to fight the fire would have accelerated the [compounds'] breakdown or dilution." To the contrary, Tullius says photographs show that some areas in the bombed facility are still intact, with the roof still in place, and that there are no signs of fire or water damage. Dismissive statements made by officials who have not examined the study and its findings serve only to exacerbate people's disbelief of the U.S. government's claims. If the U.S. government wants to be believed that the military action against the pharmaceutical plant in Sudan was justified, it should remove the veil of secrecy surrounding the analytical chemistry that helped lead to the attack. [Previous Story][Table of Contents] Chemical & Engineering News |
