Considerations for environmental sample storage, laboratory analysis, and results reporting

Abstract

A longitudinal birth cohort study, such as the U.S. National Children’s Study (NCS), presents several challenges when designing and implementing environmental sample collection, storage, analysis, and results reporting. In order to investigate many hypotheses, a variety of different types of environmental samples will be collected. Samples that cannot be stored will be analysed immediately, but for logistical reasons, many of the samples will be stored prior to analysis for an indeterminate time period. The approaches and factors that must be considered include storage stability of samples and target analytes, additional and yet unknown target analytes, maintaining analytical method comparability, and analysis results data reporting and storage. The NCS has prepared plans for storage stability studies of particulate matter, tap water, and various dust samples where quality control samples will be stored both prior to sample collection to evaluate the sample stability and stability of analytes in extracts and concurrently as the study samples are collected and stored. Based on the experiences in the Initial Vanguard Phase and experiences in other studies, the NCS plans to employ established analysis methods, when available, and consider alternate methodologies, when warranted. When analysis methods change, a number of study and stored QC samples will be analysed by both methods to maintain comparability. The NCS approach to sample analysis results reporting is to require electronic data deliverables in formats anticipated to be accessible decades after samples were collected: study and laboratory QC sample results in standardized, structured files either in XML or CSV, and the detailed measurement and background data in standard or customized data packages in PDF. The file structures and formats depend on the analytical method and target analytes in the method. The data are verified and validated before archiving.