We thank Scott for his interest in our study on background ionizing radiation and the risk of childhood cancer. Scott claims that if all random and systematic errors in measurements had been addressed, our study would likely have found no association between levels of background ionizing radiation and childhood cancer risk. We acknowledge that errors often affect estimates of long-term exposures, but there are no obvious reasons why the sum of potential measurement errors in our study, if eliminated, should result in a null finding. In fact, there are reasons to the contrary.