CIRCLE investigators, Dr. Catherine Metayer, Dr. Steve Rappaport, and Dr. Todd Whitehead, in collaboration with Dr. Mary Ward and her colleagues at the National Cancer Institute, have demonstrated that childhood leukemia is associated with exposure to a variety of residential pollutants, including polychlorinated biphenyls, polybrominated diphenyl ethers, and polycyclic aromatic hydrocarbons.  These observations were made by measuring levels of chemicals in settled dust samples collected from home participating in the California Childhood Leukemia Study.

Polychlorinated Biphenyls and Childhood Leukemia

Dr. Ward and Dr. Metayer evaluated the risk of childhood leukemia associated with exposure to six polychlorinated biphenyls and six organochlorine pesticides in the California Childhood Leukemia Study population.  The study included 184 acute lymphoblastic leukemia cases 0–7 years of age and 212 birth certificate controls matched to cases by birth date, sex, race, and Hispanic ethnicity. The investigators used concentrations of these persistent chemicals in settled dust as indicators of total exposure.  Detection of any PCB in the dust conferred a 2-fold increased risk of acute lymphoblastic leukemia. Compared with those in the lowest quartile of total PCBs, the highest quartile was associated with about a 3-fold risk. Significant positive trends in leukemia risk were apparent with increasing concentrations of PCB-118, PCB-138, and PCB-153.   This study suggested that polychlorinated biphenyls represent a previously unrecognized risk factor for childhood leukemia.  The full article is available here.

Polychlorinated biphenyls were used extensively in electrical, heat transfer, and hydraulic equipment, including in transformers and capacitors.

Polybrominated diphenyl ethers are flame retardants that were used to treat foam inside upholstered furniture.

Polybrominated Diphenyl Ethers and Childhood Leukemia

Dr. Ward and her CIRCLE colleagues evaluated the risk of childhood leukemia associated with polybrominated diphenyl ethers using the California Childhood Leukemia Study population. The investigators studied 167 acute lymphoblastic leukemia cases 0-7 years of age and 214 birth certificate controls matched on date of birth, sex, and race/ethnicity. Concentrations of 14 polybrominated diphenyl ethers were measured in settled dust collected from study homes as indicators of total exposure to these chemicals. Comparing homes in the highest concentration tertile to those with no detections, the investigators observed an increased risk of acute lymphoblastic leukemia for BDE-196, BDE-203, BDE-206, and BDE-207. The study found no association with childhood leukemia for the most abundant polybrominated dipheny ethers, but positive associations were observed for specific polybrominated diphenyl ethers with eight or nine bromine atoms, which are less abundant in the environment.  The full article is available here.

Polycyclic Aromatic Hydrocarbons and Childhood Leukemia

Dr. Deziel and her CIRCLE colleagues evaluated the risk of childhood leukemia associated with polycyclic aromatic hydrocarbons using the California Childhood Leukemia Study population.   The study included 251 children with acute lymphoblastic leukemia and 306 control children without leukemia.   Concentrations of nine polycyclic aromatic hydrocarbons were measured in settled dust collected from study homes as indicators of total exposure to these chemicals. Dust was collected using a high volume small surface sampler (N=185 cases, 212 controls) or by sampling from participants’ household vacuum cleaners (N=66 cases, 94 controls).  Among participants with dust via the high-volume small surface sampler, risk of acute lymphoblastic leukemia was not associated with increasing concentration of any polycyclic aromatic hydrocarbon.  However, among participants with vacuum dust, we observed positive associations between acute lymphoblastic leukemia risk and increasing concentrations of benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[k]fluoranthene, and indeno[1,2,3-cd]pyrene.  The increased leukemia risk among participants with vacuum dust suggests that polycyclic aromatic hydrocarbon exposure may increase the risk of childhood leukemia.  The full article is available here.

Polycyclic aromatic hydrocarbons are generated as a byproduct of incomplete combustion and have many sources, including automobile exhaust.

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