Using 1973-2000 mesothelioma incidence data released by the Surveillance, Epidemiology, and End Results Program in April 2003, the authors estimated the parameters of a birth-cohort and age model to determine whether previously reported patterns of mesothelioma in the United States have changed. Compared with analyses based on data through 1992, a slower decline was found in male cases immediately after a peak in 2000-2004, but no other notable changes in the time pattern were detected. Analysis confirmed that the annual number of male mesothelioma cases, which increased steeply from the 1970s through the mid-1990s, has leveled off in terms of both the age-adjusted rate and the absolute numbers of cases. After a peak of approximately 2,000 cases, a return to background levels is expected by 2055. The total projected number of male mesothelioma cases in 2003-2054 is approximately 71,000. The maximum lifetime risk for males, which occurs for the 1925-1929 birth cohort, is 1.8 x 10(-3). The age-adjusted rate for females is constant, as are the female lifetime mesothelioma risk across birth cohorts (3.6 x 10(-4)) and the annual risk (3.9 x 10(-6)). The time pattern of cases for females supports the existence of a threshold exposure for mesothelioma and a quantifiable background rate.

Mesothelioma incidence often is interpreted as an index of past exposure to airborne asbestos. The mesothelioma rate for US males exhibits an increasing trend throughout the 1970s and early 1980s. The trend has been attributed to occupational exposure in the shipbuilding industry during World War II, in manufacturing, and in building construction. Incidence data (1973-1992) from the Surveillance, Epidemiology, and End Results Program were used to investigate current trends in age-adjusted and age-specific mesothelioma rates. An age and birth-cohort model was used to project both lifetime probabilities of mesothelioma by cohort and the annual number of cases expected over the next 70 years. The current trend in female rates is flat (age-adjusted rate = 0.30 per 100,000). The estimated lifetime risk for females is 2.5 x 10(-4), independent of birth cohort. The projected average annual number of female cases is 500. For males, the age-adjusted mesothelioma rate is increasing solely due to the age group 75 years and over, albeit at a declining growth rate. Lifetime risk for males peaks at 2 x 10(-3) for the 1925-1929 birth cohort, then decreases to 5 x 10(-4) for the 1955-1959 birth cohort. The pattern of rates reflected in the age and birth-cohort model suggests a peak in the annual number of mesothelioma cases for males at 2,300 before the year 2000. The number of male cases then will drop during the next 50-60 years toward 500. These trends mirror the US trend in raw asbestos consumption and a reduction in workplace airborne asbestos levels.

The time trend of mesothelioma incidence and projections of future cases provide useful information for analyzing proposed public health interventions where asbestos exposure may be an issue, evaluating regulatory proposals, and estimating the remaining potential costs of programs to compensate individuals with asbestos-related diseases. We used the April 2008 release of Surveillance, Epidemiology, and End Results (SEER) data, which covers 1973 through 2005, to analyze the time trends in age-adjusted mesothelioma incidence and to estimate an age and birth-cohort model to project the number of future mesothelioma cases. The increase in the number of SEER cancer registries from 13 to 17 in 2000 had little effect on the time pattern of age-adjusted mesothelioma incidence, and the pattern over time of pleural mesothelioma was indistinguishable from the pattern for total mesothelioma defined as sum of pleural and peritoneal cases. Our analysis suggests that the SEER registries viewed as a sample of the U.S. population over-represents high mesothelioma incidence, a fact that we accounted for in our projections. For 2008 we estimate approximately 2,400 cases, with asbestos the likely cause in 58%. We project that asbestos will no longer be a factor in mesothelioma cases after the year 2042. For 2008 through 2042, we estimate slightly more than 68,000 total cases, with asbestos the likely cause in 34%.

We describe a set of criteria to evaluate the quality of data and interpretations in chemical interaction studies. These criteria reflect the consensus of the literature on interaction analysis developed over decades of research in pharmacology, toxicology, and biometry; address common pitfalls in published interaction studies; and can be easily applied to common methods of interaction analysis. The criteria apply broadly to interaction data for drugs, pesticides, industrial chemicals, food additives, and natural products and are intended to assist risk assessors who must evaluate interaction studies for use in component-based mixture risk assessments. The criteria may also assist researchers interested in conducting interaction studies to inform mixture risk assessment. The criteria are also intended to serve larger scientific goals, including increasing the repeatability of results obtained in chemical interaction studies, enhancing the reliability of conclusions drawn from interaction data, providing greater consistency of interpretations among various analysts, and decreasing uncertainty in using interaction data in risk assessments. We describe the basis for each criterion and demonstrate their utility by using them to evaluate interaction studies from the recent toxicological and pharmacological literature, which serve as examples of different types of data sets that the risk assessor may encounter.

Industrial-grade talc deposits are complex mixtures of mineral particles and may vary substantially in composition across small geographical areas. Typical industrial-grade talc includes amphibole cleavage fragments, platy talc, serpentine minerals, talc in fibrous form, and a minor presence of transitional fibers. Industrial-grade talc was erroneously determined to be an asbestos-containing material due to an unintended consequence of Occupational Health and Safety Administration's (OSHA's) method for measuring airborne asbestos mandated in 1972. This error was repeated, most notably, by the National Institute for Occupational Safety and Health (NIOSH) in, 1980 for talc mined in northern New York State (NYS) by RT Vanderbilt Company (RTV). Subsequent exposure studies of northern NYS talc conducted through the, 1980s and one study published after, 2000 relied on the conclusion that talc was an asbestos-containing material to infer a causal relationship between talc and mesothelioma. The present review included (1) publications concerning talc's cancer-causing potential issued by organizations concerned with occupational and public health; (2) talc exposure studies and animal and cellular studies of RTV talc; (3) mesothelioma rates in northern NYS; and (4) mesothelioma mortality among RTV mining employees. The review indicated that failure to correctly identify the mineral characteristics of talc resulted in misleading reports concerning the carcinogenic potential of talc. However, the collective data from animal and cellular studies, mesothelioma rates in northern NYS, exposure studies, and a mortality analysis of RTV mining employees do not support a causal relationship between RTV talc and mesothelioma. This conclusion is applicable to all mineral components in RTV talc and to other industrial-grade talcs and mineral aggregates with the same components.