Systematic review and meta-analysis of mortality in crop protection product manufacturing workers

Association of Occupational Pesticide Exposure With Immunochemotherapy Response and Survival Among Patients With Diffuse Large B-Cell Lymphoma

IMPORTANCE

Professional use of pesticides is a risk factor for non-Hodgkin lymphoma. The main biological mechanisms of pesticides and chemotherapy are genotoxicity and reactive oxygen species generation. Cellular adaptation among patients exposed to low doses of genotoxic and oxidative compounds might hinder chemotherapy efficiency in patients with lymphoma.

OBJECTIVE

To examine the association of occupational exposure to pesticides with immunochemotherapy response and survival among patients treated for diffuse large B-cell lymphoma.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study assessed patients treated from July 1, 2010, to May 31, 2015, for diffuse large B-cell lymphoma, with a 2-year follow-up. The study took place at 6 university and nonuniversity hospitals in Languedoc-Roussillon, France. A total of 404 patients with newly diagnosed diffuse large B-cell lymphoma treated with anthracycline-based immunochemotherapy were included before the study began. Occupational history was reconstructed for 244 patients and analyzed with the PESTIPOP French job-exposure matrix to determine likelihood of occupational exposure to pesticides. Analysis of the data was performed from July 15, 2017, to July 15, 2018.

MAIN OUTCOMES AND MEASURES

Treatment failure (ie, partial response, stable disease, disease progression, or interruption for toxic effects) rate, 2-year event-free survival, and overall survival between exposed and nonexposed patients after adjustment for confounding factors.

RESULTS

A total of 244 patients (mean [SD] age, 61.3 [15.2] years; 153 [62.7%] male) had complete occupational data. Of these patients, 67 (27.4%) had occupational exposure to pesticides, with 38 exposed through agricultural occupations. Occupational exposure was not associated with clinical and biological characteristics at diagnosis. Occupationally exposed patients had a significantly higher treatment failure rate (22.4% vs 11.3%; P = .03; adjusted odds ratio [AOR] for confounding factors, 3.0; 95% CI, 1.3-6.9); this difference was higher among patients with exposing agricultural occupations compared with other patients (29.0% vs 11.7%; AOR, 5.1; 95% CI, 2.0-12.8). Two-year event-free survival was 70% in the occupationally exposed group vs 82% in the unexposed group (adjusted hazard ratio [AHR] for confounding factors, 2.2; 95% CI, 1.3-3.9). Among patients with exposing agricultural occupations compared with other patients, the difference was more pronounced (2-year event-free survival, 56% vs 83%; AHR, 3.5; 95% CI, 1.9-6.5). Similarly, 2-year overall survival was lower in the group of patients with exposing agricultural occupations compared with other patients (81% vs 92%; AHR, 3.9; 95% CI, 1.5-10.0).

CONCLUSIONS AND RELEVANCE

This retrospective study showed that agricultural occupational exposure to pesticides was associated with treatment failure, event-free survival, and overall survival among patients with diffuse large B-cell lymphoma.

Incidence of Suicide in Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis

Background and Aims

Patients with inflammatory bowel disease (IBD) have higher incidence of psychosocial disorders, including depression. As suicide is the most severe manifestation of depression, we sought to identify if patients with IBD have a higher incidence of suicide through a systematic review and meta-analysis.

Methods

Systematic literature searches for articles using EMBASE and MEDLINE using Ovid were conducted to identify studies investigating suicide in IBD. Reference harvesting of the bibliographies of key articles was also performed. We included studies reporting expected number of death or standardized mortality ratio (SMR) for suicide in IBD. Meta-analysis for each IBD condition (Crohn’s disease [CD] and ulcerative colitis [UC]) was conducted separately, as well as combined.

Results

Seven cohort studies were identified through our search strategy and included in our systematic review and meta-analysis. In our analysis, the SMR for suicide in patients with IBD for all studies included was 1.20 (95% CI, 0.94–1.54). The overall pooled SMR for CD and UC were 1.36 (95% CI, 0.98–1.88) and 1.16 (95% CI, 0.8–1.69) respectively.

Conclusions

Patients with Crohn’s disease and ulcerative colitis may have an increased risk of suicide. These results highlight the importance physicians must place on ensuring the mental health of patients with IBD is both assessed and treated appropriately.

Left Atrial Appendage Electrical Isolation for Treatment of Recurrent Atrial Fibrillation: A Meta-Analysis

OBJECTIVES

In this study, the authors sought to perform a meta-analysis of controlled studies assessing the relationship between left atrial appendage (LAA) electrical isolation (EI) and recurrent atrial fibrillation (AF).

BACKGROUND

LAA triggers could play an important role in AF and can be treated with complete EI of the LAA via surgical or percutaneous approaches.

METHODS

We conducted a meta-analysis of all controlled studies published as of November 21, 2016, assessing the relationship between left atrial appendage electrical isolation (LAAEI) and recurrent AF. The primary endpoint was atrial tachycardia (AT) or AF recurrence after the post-procedure blanking period. The association between LAAEI and AT/AF was estimated using random-effects modeling. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using the DerSimonian and Laird method.

RESULTS

We identified 7 studies including 1,037 patients; LAAEI was performed in 566 patients (55%). LAAEI was associated with a significantly lower rate of AT/AF recurrence in the primary analysis (OR: 0.38; 95% CI: 0.16 to 0.90; p = 0.02). The association between LAAEI and recurrent AT/AF was strongest in a sensitivity analysis restricted to studies of percutaneous LAAEI (OR: 0.22; 95% CI: 0.11 to 0.46; p < 0.001; 5 studies, n = 623). LAAEI was not associated with thromboembolism (OR: 0.50; 95% CI: 0.18 to 1.39; p = 0.18; 5 studies, n = 767), although these studies either incorporated LAA occlusion (3 studies, n = 552 patients) or follow-up echocardiography to assess LAA function (2 studies, n = 215 patients) to inform antithrombotic strategies.

CONCLUSIONS

LAAEI is associated with a significant reduction in recurrent AT/AF. Randomized trials are required to confirm the efficacy and long-term safety of LAAEI and to determine the optimal concomitant antithrombotic strategy.

A critical review of the epidemiology of Agent Orange/TCDD and prostate cancer

To inform risk assessment and regulatory decision-making, the relationship between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and prostate cancer requires clarification. This article systematically and critically reviews the epidemiologic evidence on the association between exposure to TCDD or Agent Orange, a TCDD-contaminated herbicide used during the Vietnam War, and prostate cancer risk. Articles evaluated include 11 studies of three cohorts, four case-control or cross-sectional studies, and three case-only studies of military veterans with information on estimated Agent Orange or TCDD exposure; 13 studies of seven cohorts, one case-control study, and eight proportionate morbidity or mortality studies of Vietnam veterans without information on Agent Orange exposure; 11 cohort studies of workers with occupational exposure to TCDD; and two studies of one community cohort with environmental exposure to TCDD. The most informative studies, including those of Vietnam veterans involved in Agent Orange spraying or other handling, herbicide manufacturing or spraying workers with occupational TCDD exposure, and community members exposed to TCDD through an industrial accident, consistently reported no significant increase in prostate cancer incidence or mortality. Only some potentially confounded studies of Vietnam veterans compared with the general population, studies with unreliable estimates of Agent Orange exposure, and analyses of selected subgroups of Vietnam veterans reported positive associations. Overall, epidemiologic research offers no consistent or convincing evidence of a causal relationship between exposure to Agent Orange or TCDD and prostate cancer. More accurate exposure assessment is needed in large epidemiologic studies to rule out a causal association more conclusively.

A Systematic Review of Carcinogenic Outcomes and Potential Mechanisms from Exposure to 2,4-D and MCPA in the Environment

Chlorophenoxy compounds, particularly 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxy)acetic acid (MCPA), are amongst the most widely used herbicides in the United States for both agricultural and residential applications. Epidemiologic studies suggest that exposure to 2,4-D and MCPA may be associated with increased risk non-Hodgkins lymphoma (NHL), Hodgkin's disease (HD), leukemia, and soft-tissue sarcoma (STS). Toxicological studies in rodents show no evidence of carcinogenicity, and regulatory agencies worldwide consider chlorophenoxies as not likely to be carcinogenic or unclassifiable as to carcinogenicity. This systematic review assembles the available data to evaluate epidemiologic, toxicological, pharmacokinetic, exposure, and biomonitoring studies with respect to key cellular events noted in disease etiology and how those relate to hypothesized modes of action for these constituents to determine the plausibility of an association between exposure to environmentally relevant concentrations of 2,4-D and MCPA and lymphohematopoietic cancers. The combined evidence does not support a genotoxic mode of action. Although plausible hypotheses for other carcinogenic modes of action exist, a comparison of biomonitoring data to oral equivalent doses calculated from bioassay data shows that environmental exposures are not sufficient to support a causal relationship. Genetic polymorphisms exist that are known to increase the risk of developing NHL. The potential interaction between these polymorphisms and exposures to chlorophenoxy compounds, particularly in occupational settings, is largely unknown.

Mental health in Alberta grain farmers using pesticides over many years

BACKGROUND

Exposure to organophosphates and certain other pesticides has been related to symptoms of mental ill-health. There is particular interest in whether exposure over many years may result in chronic ill-health.

AIMS

To relate lifetime history of pesticide exposure to symptoms and medical records of mental ill-health in elderly grain farmers in Alberta.

METHODS

Two populations of grain farmers were identified for study: cohort A (n = 5986), members of an Alberta farm organization in 1983; cohort B (n = 4781), grain farmers registered with the provincial department of agriculture. In 2002-03 both groups completed a questionnaire on lifetime history of pesticide use, physician diagnosed disease and recent neuropsychological symptoms. Durations of exposure to seven pesticide components were calculated and a factor score extracted from responses to the symptom questionnaire. For a sub-cohort surviving to 2009 medical records for mental ill-health were identified. Records and symptom scores were related to pesticide exposures allowing for confounding.

RESULTS

From cohort A, 1348 and cohort B, 1078 were alive and interviewed (median age 63 years; median duration in farming 40 years): 1371 were linked to the medical records database. Mental ill-health symptom scores were related to duration of exposure to phenoxy compounds (but not to other pesticides) and to mental ill-health in medical records. Those with mental ill-health in hospital discharge records were more likely to have been exposed to phenoxy compounds for ≥35 years.

CONCLUSIONS

The relationship of long-term exposure to phenoxy herbicides and neuropsychiatric symptoms was unexpected but not explained by measured confounders.

Neurobehavioral performance among agricultural workers and pesticide applicators: a meta-analytic study

Chronic low level exposure of agricultural workers and applicators to pesticides has been found to be associated with different degrees of decrement in cognitive and psychomotor functions. The goal of this study was to use meta-analysis to (1) identify and quantify neurobehavioral deficits among agricultural workers and pesticide applicators, and (2) analyse the potential confounders or moderators of these neurobehavioral deficits. Seventeen studies, reporting on 21 independent cohort groups, were included in the meta-analysis. These studies involved 16 neuropsychological tests providing 23 different performance measures that constitute the neurobehavioral constructs. All tests and measures of the neurobehavioral functions of attention, visuomotor integration, verbal abstraction and perception constructs showed significant decrements for exposed participants. One out of three tests of memory, two of five tests of sustained attention, and four of eight tests of motor speed constructs also showed significant decrements. Nine out of these 15 effect size distributions demonstrated significant heterogeneity across cohorts. A search for cohort-level variables (eg, agricultural workers vs applicators, duration of exposure, age and percentage of male participants) to explain this heterogeneity was largely unsuccessful. However, for one test, Block Design, the duration of exposure was positively associated with performance decrements. Furthermore, it was also found that performance decrements on this test were smaller for older participants. Increasing the number of studies and using more consistent methodologies in field studies are needed.

Occupational exposures to asbestos, polycyclic aromatic hydrocarbons and solvents, and cancers of the oral cavity and pharynx: a quantitative literature review

PURPOSE

The role of occupational risk factors in oral and pharyngeal cancer is not well known and is possibly underestimated. This quantitative review summarizes epidemiological findings on exposure to asbestos, polycyclic aromatic hydrocarbons and solvents, and cancers of the oral cavity and pharynx.

METHODS

A systematic literature search was performed. We analyzed 63 publications: 8 from case-control studies and 55 from cohort studies. For agents with at least five available studies with homogenous exposure, a series of meta-analyses was conducted to provide quantitative pooled estimates of risks, using random effect models.

RESULTS

Exposure to asbestos (meta-RR 1.25; 95% CI 1.10-1.42) and to polycyclic aromatic hydrocarbons (meta-RR 1.14; 95% CI 1.02-1.28) was found to be associated with oral and pharyngeal cancer risk. On the other hand, no association was found with exposure to solvents in general (meta-RR 0.98; 95% CI 0.77-1.23) but the strong heterogeneity between studies suggested differences in exposures. The small number of studies with homogeneous exposure did not allow meta-analyses for specific solvents.

CONCLUSIONS

Future investigations should overcome common weaknesses of past studies, in terms of sample size, characterization of exposure, and classification of cancer sites.

Mortality and cancer incidence among British agricultural pesticide users

BACKGROUND

Although the acute effects of pesticides in humans are well known, uncertainty still exists about the health effects of chronic low-level exposure to pesticides.

AIMS

To compare mortality and cancer incidence experienced by a cohort of British pesticide users to that of the Great Britain (GB) population.

METHODS

The Pesticide Users Health Study (PUHS) comprises users of agricultural pesticides who have Certificates of Competence under the Control of Pesticides Regulations 1986. Participants were followed up between 1987 and 2004 (cancer incidence) or 2005 (mortality). Standardized mortality ratios (SMRs) and Standardized incidence ratios (SIRs) were estimated for outcomes of interest identified from the literature.

RESULTS

Altogether, 62,960 pesticide users were followed up for 829,709 person-years (to 31 December 2005). Most participants were male (94%) and based in England (86%). All-cause mortality was lower for both men [SMR 0.58, 95% confidence interval (CI) 0.55-0.60] and women (SMR 0.71, 95% CI 0.52-0.98) compared to the GB population. Mortality and incidence were below those expected for all cancers combined among men (SMR 0.71, 95% CI 0.66-0.77; SIR 0.85, 95% CI 0.81-0.90), particularly for cancers of the lip, oral cavity and pharynx, digestive organs and respiratory system. The incidence of testicular cancer, non-melanoma skin cancer and multiple myeloma were above expected. Mortality from injury by machinery was significantly above expected for men (SMR 4.21, 95% CI 2.11-8.42).

CONCLUSIONS

This study suggests that pesticide users in the PUHS are generally healthier than the national population but may have excesses of non-melanoma skin cancer, testicular cancer and multiple myeloma.

Assessing environmental and occupational risk factors for lung cancer in Mexican-Americans

BACKGROUND

We investigated environmental and occupational exposures and smoking history (while controlling for demographics) in a population of Mexican-American lung cancer cases and controls from the Houston metropolitan area.

METHODS

Data were collected between 1991 and 2005 as part of an on-going multi-racial/ethnic, lung cancer case-control study. Cases included 212 Mexican-American lung cancer cases from UT MD Anderson Cancer Center. Controls (n = 328) were recruited from Houston's largest multispecialty group practice and frequency matched to the cases by age (± 5 years), sex, and ethnicity. Environmental and occupational factors were analyzed and odds ratios and 95% confidence intervals were calculated using logistic regression.

RESULTS

We detected elevated risks of lung cancer associated with pesticide exposure and found conventional and antimicrobial (e.g., sterilizers, disinfectants, antiseptics) pesticides were associated with an increased risk of lung cancer in Mexican-Americans (conventional pesticides and antimicrobial pesticides combined: OR = 1.80, 95% CI 1.13-2.86; conventional pesticides: OR = 2.05, 95% CI 1.23-2.39; antimicrobial pesticides: OR = 2.48, 95% CI 1.46-4.21).

CONCLUSIONS

Although we found over a two-fold increased risk of lung cancer among Mexican-Americans for pesticides, we could not identify individual pesticides. Our findings are an important preliminary step in identifying factors that are specifically associated with lung cancer risk among Mexican Americans.