Some countries may require that exposure records be maintained by the employer for a number of years. For example, in the U.S., this record-keeping is required for at least 30 years from the date on which the exposure measurement is taken. In the EU, the requirement is for at least 40 years following exposure. Regulations generally require that employees (and possibly their representatives as well) be granted access to these records. Any exposure monitoring data gathered and recorded should be subject to rigorous quality control. The International Organization for Standards (ISO) has developed a set of useful guidelines for implementing a quality assurance program (see Appendix A for a possible contact).