Another study in collaboration with the Guandong Poison Control Center was conducted in 43 workers exposed to formaldehyde and 51 unexposed controls in 2006 to determine if formaldehyde exposure is related to increased risk for myeloid leukemia. To determine formaldehyde exposure, investigators incorporated a number of methods, including questionnaires to determine potential past exposure and on-site monitoring to determine current average and peak intensities of exposure. They found elevated levels of aneuploidy and structural abnormalities in myeloid progenitor cells cultured from peripheral blood and a decrease in peripheral cells derived from the myeloid lineage. This study has substantially contributed to our understanding of the leukemogenic potential of formaldehyde, which has important public health and regulatory implications. A substantially larger study has been recently conducted with the same collaborators to follow-up these initial findings to provide additional biological plausibility to the relationship between formaldehyde and myelogenous leukemia.