Introduction Since the 80s, more and more epidemiological studies demonstrated a relationship between agricultural exposures - especially pesticide use - and Lymphoid Malignancies (LM). However, the role of specific pesticides remains little explored.

Objective We assessed the relationship between chloroacetamide herbicide exposure (as a group and for specific molecules: acetochlore, alachlor, dimethachlore, DMTA, DMTA-p, flufenacet, S-metolachlor, metolachlor metazachlor, napropamide, pethoxamid) and LM overall and by main subtypes: multiple myeloma (MM), Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (CLL/SLL), Diffuse Large B-cell Lymphoma (DLBCL).

Methods Lifetime occupational pesticide use on 11 crops were collected from 181,842 people enrolled in the cohort AGRICAN. Incident cases were identified by cross-linkage with population-based cancer registries until 2015. Exposure to 11 chloroacetamides (ever/never) was estimated based on the crop-exposure matrix PESTIMAT.

Results Incident cases included 1,349 LM, 319 MM, 298 CLL/SLL and 221 DLBCL. Among the 51,889 pesticide users, 44% were exposed to chloroacetamides (n=22,862 including 95.4% men), ranging from 7.8% (n=4,059) for dimethachlore to 28.7% (n=14,871) for metolachlor/S-metolachlor. Positive associations were reported between chloroacetamide use on any crop and LM (HR=1.33, 95%CI=1.12–1.59), CLL/SLL (HR=1.66, 95%CI=1.15–2.39) and MM (HR=1.37, 95%CI=0.95–1.96), especially on corn. In addition, specific associations were observed in some categories of farmers: LM overall and CLL/SLL in vinegrowers, LM in beet-growers, LM and DLBLC in rape-growers and MM in potatoes-growers. Exposure to some active ingredients were significantly associated with i) LM: acetochlor, DMTA, flufenacet, alachlor, metazachlor, metolachlor (risks from 1.32 to 1.43); (ii) CLL/SLL: alachlor, metolachlor (risks from 1.75 to 1.79). Trends to increased risks were also observed between (i) LM and DMTA-p or napropamide, (ii) CLL/SLL and napropamid, (iii) MM and alachlor or metolachlor and (iii) DLBCL and dimetachlor or metazachlor.

Conclusion We found positive associations between LM overall incidences and some subtypes, and exposure to chloroacetamide as a group or considering specific molecules.