Parental occupation in farming and childhood cancer risk in I4C

Parental occupation in farming and childhood cancer risk in I4C Ann Olsson & Joachim Schüz Section of Environment and Radiation International Agency for Research on Cancer Lyon, France

Rational • Majority of case-control studies show an association • Stronger associations with indoor pesticide exposure • Internal inconsistencies, e.g. lack of dose-response • Few cohorts show no or weaker association Case-control studies are prone to bias!

Information bias Recall differences regarding maternaloccupational exposureto pesticides prior to conception Years between the date of birth and the date of the interview  cases  controls [Schüz et al., Am J Epi, 2003]

Selection bias Typical pattern: Social gradient among controls [Law, Br J Cancer, 2002]

Opportunity in I4C • Pooled prospective cohorts • Data collected prior to diagnosis • Data collected closer after “exposure” • Increased power • Standardized exposure assessment • Job titles ISCO-88 • ALOHA job exposure matrix

Farming around the world Proportion of workersemployed in agriculture By country in I4C: Australia 4.0% UK 1.8% Norway 4.4% Denmark 3.6% Israel 2.6% Global pesticide production

Challenges! • Limited occupational information • No history • No duration • Different classification systems • More or less OK to harmonize • ISCO-88 • Crude • ALOHA (one job = one exposure) • Misclassification (non-differential)

International Standard Classification of occupations ISCO-88 ILO, Geneva

ALOHA JEM Developed by H. Kromhout and R. Vermeulen (h.kromhout@uu.nl)

Exposure misclassification: between worker variability Fathers Mothers Schüz et al., Am J Epidemiol, 2003

Where we are in November 2012

Revise I4Cfarm objectives ? • Investigate if parental occupations in different types of farming is associated with increased risk of cancer in their offspring • Evaluate the risk of childhood cancer associated with self reported parental use of pesticides during pregnancy • Compare type and frequency reported in case-control studies • If possible assess whether the risk of childhood cancer associated with parental exposure to occupation as a farmer and pesticides vary by exposure time-windows (preconception, prenatal, and postnatal)

Let’s decide during this meeting! • Exposure assessment • Use the ALOHA JEM? • Focus on never vs. ever exposure? • Risk estimation • Should we wait for more studies to be included? • Compare prevalence of exposure with CLIC? • Re-code all data to look at other occupations (more frequent!) subsequently

Next steps at IARC • “Clean” the occupational data • Re-code and convert occupational data • Receive complete data sets, and additional variables from IDCC • Data analyses plan • Data analyses • Manuscript(s) (study team)

I4Cfarm – study team • LEAD - IARC/ENV (Ann Olsson, Joachim Schüz) • IARC/IMO (Kurt Straif) • NCI (Martha Linet) • MCRI (Gabriella Tikellis) • INSERM (Jacqueline Clavel) • CREAL (Martine Vrijheid) • Eligible cohorts (PI’s) • ALSPAC, DNBC, JPS, MoBA, TIHS, ?...

Thank you! olsson@iarc.fr • Welcome to the I4C Environmental Working Group BREAKOUT SESSION tomorrow at 10.00

Parental occupation in farming and childhood cancer risk in I4C