PHILADELPHIA - Rohm and Haas Co. said an 18-month review of an "apparently high number" of brain tumors among its employees found no significant links among the cases that would suggest a common cause, such as chemical exposure.

Fifteen employees at the company's Spring House, PA, research campus near Philadelphia have developed brain tumors since 1973. The tumors were malignant in 12 cases, and 11 of the employees have died. The company said about 6,000 employees have worked at the research center over the last 40 years.

Dr. Arvind Carpenter, a Rohm and Haas epidemiologist who led the study of the 12-building campus, said it was his belief that "based on the study findings and review of the current health and safety practices, Spring House is a safe place to work."

In addition to specific chemicals, the study examined work location as a risk factor. "Although several of the individuals with brain cancer worked on similar projects and in the same building during their careers, no one building or lab was found to be associated with brain cancer," the company said.

A statistical analysis for more than 100 risk factors was conducted to determine what, if any, potential workplace chemical exposures were associated with the brain-cancer cases. None were found to be statistically significant. In the analysis of building location, several of the individuals with brain cancer worked on similar projects and in the same building at one time during their careers, but in no case was there statistical significance when compared with the control population. The company said it intends to publish the study results in a peer-reviewed journal later this year.

Rohm and Haas also said it plans to begin a study of all deaths of Spring House employees, called a cohort mortality study. That review is expected to provide additional understanding of whether the number of brain-cancer cases is actually higher among employees at the site than in the general U.S. population and what, if any, other cancer rates may be prevalent.

The company said it routinely conducts epidemiological studies if there is reason to believe that workplace exposure or disease rates warrant investigation. The Spring House study was initiated as a result of concerns expressed by employees about brain cancer cases, including a recent diagnosis of one of its former researchers, as well as the publication of a similar study of brain cancer among Amoco research scientists.