In another in a series of rulings on expert issues, the MDL court in the MTBE litigation has excluded parts of the proffered testimony of a plaintiffs’ expert, while permitting others. Judge Shira Scheindlin of the U.S. District Court for the Southern District of New York issued an order permitting Dr. Myron Mehlman to testify that MTBE causes adducts to form on DNA and is a probable human carcinogen. Judge Scheindlin found that the plaintiffs proved that this part of his testimony is the product of reliable principles and methods. However, he may not testify that plaintiffs have a reasonable basis for their alleged fear of cancer.

The suits in the MDL generally allege that MTBE, which was added to gasoline at varying levels between 1979 and 2007, has leaked from underground storage tanks and contaminated groundwater. The defendants in this particular case within the MDL are the owners of two gas stations and their suppliers who allegedly contaminated 50 private water wells in the town of Fort Montgomery, N.Y. See In re: Methyl Tertiary Butyl Ether Products Liability Litigation, case number 1:00-cv-01898.

Defendants argued that Mehlman’s opinion should be excluded because his methods are not generally accepted in the scientific community and because he hadn’t applied those methods reliably to the facts. The absence of general acceptance in the community remains a relevant factor under Daubert.

The court noted that if a method hasn’t gained general acceptance, it may be properly viewed with skepticism. But “viewing a method with skepticism is a far cry from the bright-line rule of exclusion.” The expert relied on the peer reviewed MTBE-DNA Adducts study, as well as numerous studies allegedly showing exposure to MTBE has led to cancer in animals. The court held that a vigorous cross examination by defendants at trial was the proper way to handle the issues concerning the expert’s methodology as well as its underlying assumptions. “After evaluating the evidence from both sides, the jury may well agree with defendants that MTBE does not cause cancer in humans,” the court noted.

However, the expert cannot testify that specific plaintiffs suffered subcellular damage or have a reasonable fear of cancer because he did not adequately quantify their alleged exposure. While the levels of exposure to toxic substances is sometimes difficult to precisely quantify, this does not excuse Dr. Mehlman from attempting to analyze plaintiffs’ exposure levels if he intended to testify that they have a basis for their fear of cancer.