Le novità del registro

Do children of parents who are exposed to benzene at work have a higher risk of cancer?

Summary of results

Our research question

We investigated whether children of parents exposed to benzene at their workplace were more likely to develop cancer than children of parents without such exposure.

Why is this important?

Benzene is a substance that was widely used in the past as a solvent in paints and glues. In adults exposed to high levels of benzene at work, it can cause cancers of the blood, particularly acute myeloid leukaemia (AML), but possibly also acute lymphoid leukaemia (ALL) and non-Hodgkin lymphoma. It is unclear whether children of exposed parents also have an increased risk of such cancers. If so, this could indicate that even low levels of exposure might increase childrens’ risk of developing cancer. Children are exposed to small amounts of benzene in the air they breathe. Important sources include traffic-related air pollution or second-hand tobacco smoke.

What did we do?

We included all children aged less than 16 years covered by the Swiss national censuses in 1990 and 2000. For most of these children, we were able to obtain the occupations of one or both of their parents from the census data. This allowed us to identify parents who were likely exposed to high levels of benzene at work. By matching the anonymous information from the censuses with information from the Swiss Childhood Cancer Registry, we were able to identify which of the children included in the study later developed a cancer. We then compared the risk of developing cancer in children of parents exposed to benzene at work to that in children of parents with no or only low levels of exposure. 

What did we find?

We estimated benzene exposure for mothers of about 1.1 million children and for fathers of about 1.5 million children. The proportion of parents likely exposed to significant levels of benzene was about 6% for mothers (including occupations such as cleaners, lab technicians, painters and occupations in the printing industry) and 14% of fathers (including painters, plumbers, cabinet makers, mechanics and many others). In children of exposed mothers, the risk of developing leukaemia was about 70% higher than in other children. The risk was particularly increased for ALL and in children who were younger than 5 years of age at the time of census when the occupations were assessed. We found no evidence for increased risks for other cancers such as brain tumours or lymphoma, nor was there evidence of increased risks among children of exposed fathers.

What does this mean?

Our study suggests that mothers’ exposure to benzene at work increases the risk of leukaemia in their children. We cannot exclude the possibility that the observed risk increase was due to factors other than benzene, to errors in the study or to chance. If the cause was indeed benzene, mothers’ exposure at work could explain about 3% of leukaemia diagnoses in children during the study period (1990-2008). Benzene can be transmitted to the child by crossing the placenta during pregnancy, through breastfeeding or through contamination of the clothes brought home from work. However, benzene has largely been replaced by less dangerous substances and workplace levels are much lower today than at the beginning of the study period. Nevertheless, the small amounts of benzene that children breathe in from traffic-related air pollution and second-hand smoke might also increase their risk of cancer.

More information:

Ben Spycher, Email : ben.spycher@ispm.unibe.ch

Spycher et al., Environment International 2017;108:84-91

© ISPM - Università di Berna 2019