Exposure to non-arsenic pesticides is associated with lymphoma among farmers in Spain

Our plain-English summary of Exposure to non-arsenic pesticides is associated with lymphoma among farmers in Spain, by E. van Balen, R. Font, N. Cavallé, et al (Occupational and Environmental Medicine, 2006).

The study

• Authors: E. van Balen, R. Font, N. Cavallé, L. Font, M. Garcia-Villanueva, Y. Benavente, P. Brennan, S. de Sanjose
• Journal: Occupational and Environmental Medicine
• Published: 2006;63(10):663-8
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: To estimate the risk of lymphoma among farmers in Spain.

Methods: This is a multicentre case control study conducted in Spain. Cases were subjects diagnosed with lymphoma according to the World Health Organization (WHO) classification in four hospitals between 1998-2002. Hospital controls were frequency matched to the cases by sex, age, and centre. All subjects were interviewed about jobs ever held in lifetime for at least one year and the exposures in those jobs were recorded. The risk of lymphomas among subjects ever having had a job as a farmer was compared with all other occupations. Farmers were analysed according to the type of farming job performed: crop farming, animal farming, and general farming. Occupational exposure was summarised into 15 main categories: organic dust, radiation, contact with animals, PAH, non-arsenic pesticides (carbamates, organophosphates, chlorinated hydrocarbons, triazines and triazoles, phenoxy herbicides, chlorophenols, dibenzodioxin, and dibenzofuran), arsenic pesticides, contact with meat, contact with children, solvents, asbestos, soldering fumes, organic colourants, polychlorinated biphenyls, ethylene oxide, and hair dyes.

Results: Although farmers were not at an increased risk of lymphoma as compared with all other occupations, farmers exposed to non-arsenic pesticides were found to be at increased risk of lymphoma (OR = 1.8, 95% CI 1.1 to 2). This increased risk was observed among farmers working exclusively either as crop farmers or as animal farmers (OR = 2.8, 95% CI 1.3 to 5.8). Risk was highest for exposure to non-arsenic pesticides for over nine years (OR = 2.4, 95% CI 1.2 to 2.8).

Conclusions: Long term exposure to non-arsenic pesticides may induce lymphomagenesis among farmers.

In plain English

This hospital-based case-control study in four Spanish hospitals compared 587 adults newly diagnosed with lymphoma between 1998 and 2002 with 628 hospital patients without lymphoma. Participants were interviewed about every job held for at least a year, and experts unaware of who had lymphoma rated exposures, including pesticides and asbestos. Having ever farmed was not linked to higher lymphoma risk (odds ratio 1.02, 95% CI 0.78 to 1.34). Farmers exposed to non-arsenic pesticides had higher odds of lymphoma than unexposed farmers (OR 1.8, 95% CI 1.1 to 2.9). For crop and animal farmers the figure was 2.8 (1.3 to 5.8). Among all farmers, odds were highest for 9 to 17 years of exposure (OR 2.4, 1.2 to 4.8); for crop and animal farmers that figure was 4.2 (1.4 to 12.6), with no statistically significant trend across durations. Among farmers, asbestos exposure was not significantly linked to lymphoma (OR 1.2, 0.7 to 2.0). The authors concluded that farmers exposed to non-arsenic pesticides were at increased risk. Exposure information came from memory, and exposure intensity was not analysed.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Multicentre hospital-based case-control study, part of the European Epilymph study
• Who was studied: 587 lymphoma cases (adults over 19, newly diagnosed 1998 to 2002) and 628 hospital controls, frequency matched by sex, age and centre, from four centres in Spain (one in Barcelona, two in Tarragona, one in Madrid). 383 subjects had ever worked as farmers.
• Exposure: Ever working as a farmer (crop, animal or general farming), and 15 occupational exposure categories assessed by a hygienist and an exposure expert from lifetime job histories. The categories included non-arsenic pesticides (carbamates, organophosphates, chlorinated hydrocarbons, triazines and triazoles, phenoxy herbicides, chlorophenols, dibenzodioxin, dibenzofuran), arsenic pesticides, solvents and asbestos. Hair dyes, ethylene oxide and PCBs were left out of the analysis because very few people had been exposed to them.
• Main results:
  • Ever farmers compared with never farmers: no significantly raised risk of all lymphoma (193 controls and 190 cases; OR 1.02, 95% CI 0.78 to 1.34). Farming as longest occupation: OR 1.25 (0.88 to 1.77), not statistically significant.
  • Compared with never farmers, general farmers had OR 1.4 (95% CI 1.0 to 2.0) for all lymphoma. Crop farmers (OR 0.7, 0.5 to 1.1) and animal farmers (OR 0.8, 0.4 to 1.3) had no increased risk.
  • All farmers ever exposed to non-arsenic pesticides compared with non-exposed farmers (52 controls and 63 cases exposed): OR 1.8, 95% CI 1.1 to 2.9.
  • Crop and animal farmers ever exposed to non-arsenic pesticides (26 controls and 26 cases): OR 2.8, 95% CI 1.3 to 5.8. For general farmers (26 controls and 37 cases) the OR was 1.3, 95% CI 0.7 to 2.5, not significant.
  • Exposure to non-arsenic pesticides for 9 to 17 years: OR 2.4 (1.2 to 4.8) for all farmers and OR 4.2 (1.4 to 12.6) for crop and animal farmers. For 1 to 8 years the OR in all farmers was 1.5 (0.7 to 3.2), and for 18 to 60 years it was 1.7 (0.8 to 3.5). The test for trend was not significant (p = 0.80 for all farmers).
  • Asbestos exposure among farmers was not significantly associated with lymphoma. All farmers: 41 controls (21.2%) and 39 cases (20.5%) exposed, OR 1.2 (0.7 to 2.0). Crop and animal farmers: OR 0.9 (0.4 to 2.1). General farmers: OR 1.2 (0.6 to 2.3).
• The authors' conclusion: The authors concluded that farmers exposed to non-arsenic pesticides were at increased risk of lymphomas. They said the risk was clearly observed for crop and animal farmers and was greatest for 9 to 17 years of exposure. In the abstract they wrote that long-term exposure 'may induce' lymphoma development, and they called for the association to be monitored closely.
• Limitations the authors state:
  • Exposure could not be measured directly and was based on lifetime recall in interviews, so recall bias cannot be excluded.
  • Many subjects could not name specific pesticide products, so more specific pesticide information is unavailable.
  • Level or concentration, frequency and probability of exposure were not evaluated.
  • Duration of exposure within farming jobs was sometimes difficult to estimate.
  • Farm owners and managers were counted as farmers but may not have applied pesticides themselves.
  • If sunlight protects against non-Hodgkin's lymphoma, near-universal sun exposure among farmers may have diluted the results.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure.

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