Incidence rates of lymphomas and environmental measurements of phenoxy herbicides: ecological analysis and case-control study

Passive environmental residential exposure to agricultural pesticides and hematological malignancies in the general population: a systematic review

Incidence rates of hematological malignancies have been constantly increasing over the past 40 years. In parallel, an expanding use of agricultural pesticides has been observed. Only a limited number of studies investigated the link between hematological malignancies risk and passive environmental residential exposure to agricultural pesticides in the general population. The purpose of our review was to summarize the current state of knowledge on that question. A systematic literature search was conducted using PubMed and Scopus databases. We built a scoring scale to appraise relevance of each selected articles. We included 23 publications: 13 ecological studies, 9 case-control studies and a cohort study. Positive associations were reported between hematological malignancies and individual pesticides, pesticide groups, all pesticides without distinction, or some crop types. Relevance score was highly various across studies regardless of their design. Children studies were the majority and had overall higher relevance scores. The effect of passive environmental residential exposure to agricultural pesticides on hematological malignancies risk is suggested by the literature. The main limitation of the literature available is the high heterogeneity across studies, especially in terms of exposure assessment approach. Further studies with high methodological relevance should be conducted.

Phenoxy herbicides, soft-tissue sarcoma and non-Hodgkin lymphoma: a systematic review of evidence from cohort and case-control studies

BACKGROUND

Phenoxy herbicides have been used widely in agriculture, forestry, parks and domestic gardens. Early studies linked them with soft-tissue sarcoma (STS) and non-Hodgkin lymphoma (NHL), but when last reviewed by the International Agency for Research on Cancer in 1986, the evidence for human carcinogenicity was limited.

SOURCES OF DATA

We searched Medline and Embase, looking for cohort or case-control studies that provided data on risk of STS and/or NHL in relation to phenoxy herbicides, and checked the reference lists of relevant publications for papers that had been missed.

AREAS OF AGREEMENT, AREAS OF CONTROVERSY

The extensive evidence is not entirely consistent, and a hazard of STS or NHL cannot firmly be ruled out. However, if there is a hazard, then absolute risks must be small.

GROWING POINTS, AREAS TIMELY FOR DEVELOPING RESEARCH

Extended follow-up of previously assembled cohorts may be the most efficient way of further reducing uncertainties.

Increased incidence of malignant melanoma and other rare cutaneous cancers in the setting of chronic lymphocytic leukemia

BACKGROUND

Patients with chronic lymphocytic leukemia (CLL), small lymphocytic lymphoma (SLL), or non-Hodgkin lymphoma (NHL) are at increased risk for the development of skin malignancies.

OBJECTIVES

This study was conducted to estimate the incidences of rare skin malignancies in patients with CLL/SLL or NHL.

METHODS

Patients with a diagnosis of CLL/SLL or NHL recorded in the Surveillance, Epidemiology and End Results (SEER) database during 1992-2007 were identified. Diagnoses of specific skin malignancies were identified from SEER files.

RESULTS

During 1992-2007, a total of 128,674 patients with first diagnoses of CLL/SLL or NHL were recorded in SEER; 4743 were excluded because follow-up data were unavailable. Among the remaining 123,931 patients, 28,964 had CLL/SLL and 94,967 had NHL. Standardized incidence ratios (SIRs) for invasive malignant melanoma, Merkel cell carcinoma, malignant fibrous histiocytoma, dermatofibrosarcoma protuberans, Kaposi's sarcoma, and sebaceous carcinoma were 2.3, 8.2, 3.6, 2.5, 2.9, and 1.4, respectively, in CLL/SLL patients and 1.6, 3.2, 1.5, 1.3, 17.6, and 0.8, respectively, in NHL patients. When invasive melanoma was stratified by patient age and sex, the highest SIR (17.8) was found in men aged 0-49 years with CLL (P < 0.001).

CONCLUSIONS

Patients with CLL/SLL or NHL have a higher risk for the subsequent development of rare skin cancers. Given the more aggressive nature of these malignancies in this setting, regular monitoring for the development and prompt treatment of cutaneous malignancy is prudent in patients with NHL and particularly in patients with CLL. Regular use of sun protection may decrease the morbidity associated with skin cancer in this immunosuppressed population.

TCDD and cancer: a critical review of epidemiologic studies

The authors reviewed the epidemiologic studies on exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and cancer risk, published since the last full-scale review made by the International Agency for Research on Cancer Monographs program in 1997. The update of a cohort of US herbicide producers generated negative results overall; the internal analysis provided evidence of an increased "all-cancer" risk in the highest exposure category, with a statistically significant exposure-response association in some of the many analyses performed. The update of a similar Dutch cohort did not confirm the previously observed association with TCDD exposure. The updated surveillance of the Seveso population provided evidence of increased all-cancer mortality 15-20 years after exposure among those living in the most contaminated area but might also reflect random variation, as overall excesses in the most recent follow-up were not observed. Corresponding data on cancer incidence offer little support to the mortality results. Updated results from cohort studies of Vietnam veterans potentially exposed to TCDD did not consistently suggest an increased risk of cancer. Results of additional, smaller studies of other occupational groups potentially exposed to TCDD, and of community-based case-control studies, did not provide consistent evidence of an increased cancer risk. In conclusion, recent epidemiological evidence falls far short of conclusively demonstrating a causal link between TCDD exposure and cancer risk in humans. The emphasis on results for overall cancer risk-rather than risk for specific neoplasms-is not justified on epidemiologic grounds and is not a reason for ignoring the weaknesses of the available evidence.

Occupation and the risk of non-Hodgkin lymphoma

Although thus far no occupational agents have been classified as established causes of non-Hodgkin lymphoma (NHL), employment as a farmer, teacher, dry cleaner, meat worker, printer, or wood worker has been associated with elevated risk in the peer-reviewed literature. We conducted several meta-analyses to assess risk in these occupations and industries from articles published in MEDLINE up to August 1, 2006. The summary risk estimates suggest a homogeneous excess risk for NHL among workers in the printing industry [relative risk (RR), 1.86; 95% confidence interval (95% CI), 1.37-2.52] and wood workers (RR, 1.15; 95% CI, 1.00-1.31). Considerable heterogeneity but elevated risks were found for farmers (RR, 1.11; 95% CI, 1.05-1.17), especially in animal husbandry (RR, 1.31; 95% CI, 1.08-1.60), and teaching (RR, 1.47; 95% CI, 1.34-1.61). An increased risk was absent for employment in the meat processing industry (RR, 0.99; 95% CI, 0.77-1.29). These results suggest that although excess risk is found for employment in the printing industry, wood processing industry, teaching, and farming, it is unlikely that occupation represents a major risk factor for NHL in most populations. At present, no conclusive evidence of causal relations between occupations and increased NHL risk exists; this can be ascribed to methodologic problems in studying the link between NHL risk and occupation, including heterogeneity of disease and exposure circumstances and low statistical power. Implementing state-of-the-art exposure assessment technologies, including biomarker-based assessment, and aiming to identify susceptible subgroups can increase the statistical power enough to analyze etiologically relevant NHL subtypes and provide clues on possible causal agents in future studies. These goals can be best attained within the framework of large-scale, international collaborative projects.

Residential proximity to industrial plants and non-Hodgkin lymphoma

BACKGROUND

A U.S. analysis suggested a relation between self-reported residential proximity to industrial plants and non-Hodgkin lymphoma (NHL) risk.

METHODS

Using lifetime residential histories collected from a population-based sample of 1499 Canadians with newly diagnosed, histologically confirmed NHL and 5039 population controls, we evaluated the association of residential proximity to 7 types of major heavy industry with NHL risk.

RESULTS

Overall, having lived within 0.8 km or within 3.2 km of an industrial plant was not associated with increased NHL risk. For the follicular subtype of NHL, an odds ratio (OR) of 1.48 (95% confidence interval [CI] = 1.10-1.99) was observed for women who had lived within 3.2 km (83 cases/689 controls). ORs for NHL were elevated for proximity within 3.2 km of copper smelters (OR = 5.1; CI = 1.5-17.7; 7 cases, 4 controls) and within 0.8 km of sulfite pulp mills (OR = 3.7; CI = 1.5-9.4; 9 cases, 10 controls).

CONCLUSIONS

We have identified possible associations between NHL and proximity to industrial plants, which could be the result of chance or other factors associated with proximity. Studies are needed to confirm these associations and to determine whether residential proximity can result in meaningful exposure.

Effects of selected herbicides on cytokine production in vitro

To evaluate possible deleterious effects of commonly used herbicides on leukocytes, cytokine production was selected as a sensitive indicator. After in vitro exposure of human peripheral blood mononuclear cells from normal donors, the production of all 3 cytokines tested--interferon-gamma (a type 1 cytokine), interleukin-5 (a type 2 cytokine) and tumor necrosis factor-alpha (an inflammatory cytokine)--was impaired by up to 70, 50 and 70% respectively in a concentration-dependent manner in cultures exposed to atrazine (0.03-3 microM in 1% dimethylsulfoxide, DMSO). The effect paralleled that seen with dexamethasone, a known immunosuppressive agent. Other pesticides also dissolved in DMSO--mecoprop, simazine or MCPA (each up to 1 microM)--or dissolved in phosphate-buffered saline--diuron (up to 1 microM), isoproturon (up to 3 microM), metoxuron (up to 8 microM) or metamitron (up to 80 microM)--showed no concentration-related effects on cytokine production. There was, however, an inhibition of IFN-gamma and TNF-alpha production by simazine, metoxuron and mecoprop and of all three cytokines tested by diuron. MCPA (0.01 and 0.1 microM) stimulated the production of TNF-alpha. Thus, exposure to herbicides leading to plasma levels in the micromolar range induces imbalance in cytokine production.

Benzene and non-Hodgkin's lymphoma

Incidence rates for non-Hodgkin's lymphoma (NHL) have been rising throughout the world for several decades, and no convincing explanation exists for the majority of this increase. The commonest subtypes of NHL have no well-defined aetiological factors but lymphoma development has been linked with exposure to a variety of chemicals, including nitrates, pesticides, herbicides, and solvents. Benzene, a solvent and important constituent of petrochemical products, is a potent lymphomagen in experimental animals and high-dose exposure in humans is associated with both acute myeloid leukaemia and NHL. Much current interest centres on the possibility that environmental benzene exposure in the general public may underlie a proportion of the increase in NHL. Seventy per cent of benzene exposure in the environment is derived from vehicle exhaust emissions, whose increase has closely paralleled the rise in frequency of the disease. Mathematical modelling has been used to calculate an acceptable concentration of benzene in air based on risk estimates derived from industrial exposure, but the recommended target concentration in the U.K. of 1 ppb is regularly exceeded in urban locations. Detailed investigation of the health effects of low-level benzene exposure awaits an accurate assay for quantifying long-term human exposure. The (32)P post-labelling technique for the detection of toxin-specific DNA adducts is extremely sensitive and has been applied in the biomonitoring of exposure to a number of carcinogens, but benzene-DNA adducts have to date proved elusive of detection.