The EPA has instituted an environmental data assurance system so that environmental protection decisions can be made based on accurate environmental data. The EAL ensures that testing data have complied with data quality elements including precision, accuracy, completeness, representativeness, and comparability.

EAL's quality control and assurance assessments process is based on the EPA document “Quality Assurance Implementation Program for Test Data used in the EPA's Contractual Projects”.

All of the EPA's contractual projects that concern measurement are required to propose quality assurance project plans (QAPJP) in advance. The EAL arranges for theseQAPJPs to be reviewed by scholars and experts. In addition ， lab data quality on the contractual projects is audited by academic institutions every year to help laboratories correct and improve their test data quality. To date approximately 40 extramural projects have been reviewed each year.

The EAL has also developed an integral and effective internal quality control system covering delivery of samples, quality control sample analysis, and quality control checking. This system is based on the general rules of QC in environmental laboratories and the related QC guideline documents. To maintain consistency, these procedures are to be adopted by laboratories throughout the nation.