Childhood brain tumours and exposure to animals and farm life: a review

Brain tumours are the most common solid tumour in children. However, little is known about their aetiology, and only a small percentage of cases can be attributed to established risk factors. Exposure to farm animals and pets have been considered as possible risk factors for childhood brain tumour (CBT) development for several reasons. Numerous. factors associated with farm life, including bacteria, pesticides, solvents and some animal oncogenic viruses, have been found to induce brain tumour formation in animals. Some studies have found viral gene sequences in human brain tumours. Epidemiological studies of brain tumours in adults have reported an increased risk among veterinarians and farmers. In this review, data are examined from seven case-control studies published between 1979 and 1998 that considered a possible relationship between fetal or childhood exposure to farm animals or pets and CBT. Five of the seven studies examined childhood farm residence or exposure of mother or child to farm animals and, of these five, four reported elevated risk for CBT with odds ratios (OR) ranging from 0.9 to 2.5 for maternal exposures and from 0.6 to 6.7 for children's exposures. Later studies that were larger subsequently examined histological type and reported excess risk for primitive neuroectodermal tumours (PNETs) with farm residence prenatally (OR = 3.7, CI = 0.8, 24) or in childhood (OR = 5.0, CI = 1.1, 4.7). Increased risk of PNET was also associated with maternal exposure to pigs (OR = 12, CI = 1.1, 47) or poultry (OR = 4.0, CI = 1.2 13). The results of these studies showed few other consistent relationships between farm life or farm animals and CBT.