Cancer incidence among alachlor manufacturing workers

Am J Ind Med. 1996 Sep;30(3):300-6. doi: 10.1002/(SICI)1097-0274(199609)30:3<300::AID-AJIM8>3.0.CO;2-1.


A historical cohort study was conducted to evaluate cancer incidence among chemical workers with occupational and environmental exposure to alachlor, the active ingredient in a family of pre-emergent acetanilide herbicides. The study followed 943 workers with at least 1 year of cumulative employment at the Monsanto plant in Muscatine, Iowa, from startup of the alachlor manufacturing process in March 1968 through December 1990. Approximately 96% of all workers were successfully traced to determine their last known residence and cancer status. Eighteen workers were diagnosed with cancer during the follow-up period, based on pathology information from the statewide cancer registry maintained by the State Health Registry of Iowa. The standardized incidence ratio for all cancers was 1.5 (95% CI 0.9-2.4) for all workers exposed to alachlor, which was due primarily to elevated rates for colorectal cancer and chronic myeloid leukemia. Workers with 5 or more years in estimated high alachlor exposure jobs had elevated rates of colorectal cancer (3 cases, SIR = 5.2, 95% CI 1.1-15.1). Interpretation of the study results is limited by the small size of the study population, minimal length of follow-up, and current information concerning alachlor metabolism in primates and humans. Nonetheless, the findings suggest the need for continued evaluation of this and other alachlor-exposed cohorts.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetamides / adverse effects*
  • Adult
  • Cohort Studies
  • Colorectal Neoplasms / chemically induced
  • Colorectal Neoplasms / epidemiology
  • Confidence Intervals
  • Female
  • Follow-Up Studies
  • Herbicides / adverse effects*
  • Humans
  • Incidence
  • Iowa / epidemiology
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / chemically induced
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / epidemiology
  • Male
  • Neoplasms / chemically induced*
  • Neoplasms / epidemiology
  • Occupational Diseases / chemically induced*
  • Occupational Diseases / epidemiology
  • Occupational Exposure*
  • Odds Ratio
  • Registries
  • Retrospective Studies
  • Time Factors
  • Water Supply


  • Acetamides
  • Herbicides
  • alachlor