Like the word "chemical," the word "pesticide" has been hijacked and then unfairly demonized.

Scientists use the word pesticide to refer to "any chemical, generally used in an agricultural setting, that can be used to kill another unwanted organism." Pesticides can be natural or synthetic, and they can be used to kill plants (herbicides), insects (insecticides), fungi (fungicides), or rodents (rodenticides).

Society uses the word pesticide pejoratively, assuming that anything that can kill another organism can also kill humans. This is almost never true. It is biologically impossible for some pesticides, such as Bt toxin, to harm humans. And the pesticides that can harm humans are used at such low concentrations that their presence has no effect on us.

Despite this, the word pesticide continues to carry a lot of negative emotional baggage. It's little wonder, therefore, that pesticides have been blamed (usually incorrectly) for all sorts of problems, from environmental pollution to cancer. Nothing is more emotionally charged than pediatric cancer, and pesticides have been blamed for that, too. But is it true?

Increase in Childhood Cancer Is Not Due to Pesticide

A new study published in The Lancet Oncology examined the incidence of pediatric cancer from 1991 to 2010. It was a gigantic study that included 1.3 billion person-years. (One "person-year" is an epidemiological term that refers to one person being studied for a period of one year. Ten person-years could be one person studied for ten years, two people studied for five years, five people studied for two years, etc.) The study found:

During the past three decades, incidence increased by about 1% per annum for all cancers combined and this increase affected most major diagnostic groups, including leukaemias, lymphomas, and CNS [central nervous system] tumours. However, in the past decade, incidence appears to have stabilised overall and for the major diagnostic groups in European populations.

In other words, pediatric cancer rates have stabilized after a period in which they were increasing. Why were they increasing?

To put it bluntly, we don't really know. The authors propose that improvements in diagnosis and reporting likely explain some of the data. People with bizarre agendas insist that pediatric cancer is due to Wi-Fi, cell phones, or chemicals, but that is total nonsense. Though it was not the goal of this analysis to investigate etiology, it does provide a hint that pesticides are probably not responsible for pediatric cancer, either.

In an accompanying commentary, Belgian cancer epidemiologist Philippe Autier writes:

Another contrast across European regions concerns the use of pesticides in agriculture. In 2014, the quantities of pesticide sales per capita were about three times greater in Spain, Italy, and France than in Sweden or the UK. If increasing cancer incidence trends were due to pesticides, dissimilarities in incidence trends for leukaemia and lymphoma would be expected between European regions, which was not the case.

Put another way, if pesticides cause pediatric cancer, then countries that use more pesticides should have more cases of pediatric cancer. But they don't. Therefore, pesticides probably don't cause pediatric cancer.

The bottom line is that more research is necessary to uncover the causes of childhood cancer. But eliminating unlikely candidates, such as pesticides, is an important step in unraveling the mystery.

Source: Eva Steliarova-Foucher, et al. "Changing geographical patterns and trends in cancer incidence in children and adolescents in Europe, 1991–2010 (Automated Childhood Cancer Information System): a population-based study." Lancet Oncology. Published: 8-August-2018. DOI: 10.1016/S1470-2045(18)30423-6

Source: Philippe Autier. "Increasing incidence of cancer in children and competing risks." Lancet Oncology. Published: 8-August-2018. DOI: 10.1016/S1470-2045(18)30498-4