Case-control study on concentrations of organohalogen compounds and titers of antibodies to Epstein-Barr virus antigens in the etiology of non-Hodgkin lymphoma

Interplay between Epstein-Barr virus infection and environmental xenobiotic exposure in cancer

Epstein-Barr virus (EBV) is a herpesvirus associated with lymphoid and epithelial malignancies. Both B cells and epithelial cells are susceptible and permissive to EBV infection. However, considering that 90% of the human population is persistently EBV-infected, with a minority of them developing cancer, additional factors are necessary for tumor development. Xenobiotics such as tobacco smoke (TS) components, pollutants, pesticides, and food chemicals have been suggested as cofactors involved in EBV-associated cancers. In this review, the suggested mechanisms by which xenobiotics cooperate with EBV for carcinogenesis are discussed. Additionally, a model is proposed in which xenobiotics, which promote oxidative stress (OS) and DNA damage, regulate EBV replication, promoting either the maintenance of viral genomes or lytic activation, ultimately leading to cancer. Interactions between EBV and xenobiotics represent an opportunity to identify mechanisms by which this virus is involved in carcinogenesis and may, in turn, suggest both prevention and control strategies for EBV-associated cancers.

Distribution characteristics and environmental fate of PCBs in marine sediments at different latitudinal regions: Insights from congener profiles

Sediments were sampled from Hangzhou Bay (HB), the South China Sea (SCS), and Antarctica (AZ) to better understand the distribution characteristics and environmental fate of polychlorinated biphenyls (PCBs) at different latitudes. Numerous PCB congeners (68) were detected among the sampling sites, supporting the ubiquity of PCB congeners. High and low chlorinated congeners dominated the PCB profiles of AZ and SCS, respectively, whereas the PCB homologues were evenly distributed in the HB. As a fraction of low chlorinated PCBs originates from an exogenous input, the low mean ratios of ∑Tetra-CBs to ∑PCBs and ∑Tetra-CBs to the sum of ∑Tri- and ∑Di-CBs suggest that microbial transformation of PCBs is weak in marine surface sediments, if any occurs at all. Furthermore, PCB contamination levels in marine sediments may be primarily influenced by latitude rather than pollution sources. Thus, the findings of this study suggest that Antarctica is becoming a prospective hotspot for PCBs.

Prediagnostic serum concentrations of organochlorine pesticides and non-Hodgkin lymphoma: A nested case-control study in the Norwegian Janus Serum Bank Cohort

BACKGROUND

Much of the marked increase in incidence of non-Hodgkin lymphoma (NHL) over the past few decades remains unexplained. Organochlorines, including organochlorine pesticides (OCPs), have been implicated as possible contributors to the increase, but the evidence is inconsistent.

OBJECTIVES

To investigate the relation between pre-diagnostic levels of OCPs and risk of NHL in a case-control study nested within the population-based Janus Serum Bank Cohort in Norway.

METHODS

Prediagnostic concentrations of 11 OCPs or OCP metabolites were measured in baseline blood samples collected between 1972 and 1978 from 190 cases and 190 controls matched on sex, county, age at blood draw, and date of blood draw. We conducted conditional logistic regression to estimate adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs) for each quartile of lipid-corrected OCP/metabolite relative to the lowest quartile.

RESULTS

We observed non-significantly elevated ORs across quartiles of β-hexachlorocyclohexane compared to the lowest quartile (OR range: 1.40-1.82) although with no apparent monotonic exposure-response relationship. We also found an inverse association between risk of NHL and o,p'-DDT (OR for Q₄ vs. Q₁ = 0.44, 95% CI: 0.19, 1.01; p-trend = 0.05). In analyses stratified by age at blood collection and duration of follow-up, several other analytes, primarily chlordane-related compounds, showed inverse associations among younger participants or those with longer follow-up time between blood draw and NHL diagnosis.

CONCLUSIONS

We found only limited evidence of positive association between selected OCPs and development of NHL.

Do polychlorinated biphenyls cause cancer? A systematic review and meta-analysis of epidemiological studies on risk of cutaneous melanoma and non-Hodgkin lymphoma

In 2015 a IARC Working Group upgraded the classification of PCBs to Group 1 "Carcinogenic to humans", also on the basis of evidence from epidemiological studies showing an excess risk for melanoma. Increased risks for non-Hodgkin lymphoma (NHL) and breast cancer were also reported though the evidence was limited. However, some recent reviews of studies on PCB exposure and risk of cancer provided discrepant findings. Therefore, we re-evaluated the association between exposure to PCBs and risk of melanoma and NHL by a systematic review and meta-analysis. We retrieved 11 independent cohort studies on occupationally exposed workers. About half of them showed increased standardized mortality or incidence ratios (SMRs or SIRs) for melanoma and none for NHL. The pooled SMRs were 1.32 (95% CI: 1.05-1.64) for melanoma and 0.94 (0.73-1.23) for NHL. Among population-based cohort and case-control studies with individual measures of PCB exposure, one only study was carried out on PCB exposure and melanoma, showing an odds ratio (OR) of 6.0 (2.0-18.2) for the highest compared to lowest quartile of PCB distribution. 13 cohort and case-control studies evaluated the association between NHL and PCB concentration in blood or subcutaneous fat, with summary OR = 1.5 (1.1-1.7) for the highest vs lowest quantile of PCB distribution. However, two cohort studies on people intoxicated by rice oil containing PCBs found no excess of deaths for skin cancer and inconsistent results for NHL. In conclusion, these findings do not provide a strong evidence that PCB exposure can increase the risk of melanoma and NHL in humans.

Exposure to organochlorine pesticides and non-Hodgkin lymphoma: a meta-analysis of observational studies

Growing evidence indicates that exposure to organochlorine pesticides (OCPs) could increase non-Hodgkin lymphoma (NHL) risk. However, results from epidemiological studies investigating this association remain controversial. We thus conducted a meta-analysis to quantitatively evaluate the association between OCP exposure and NHL risk. Relevant publications were searched in PubMed, Web of Science, and Embase and identified according to the inclusion criteria. Thirteen studies (6 nested case-control, 1 case-cohort, and 6 case-control) were selected for this meta-analysis. We used odds ratios (ORs) with 95% confidence intervals (CIs) to estimate the relationship between OCPs exposure and NHL risk. The summary OR for included studies was 1.40 (95% CI 1.27 to 1.56). No overall significant heterogeneity in the OR was observed (Ph = 0.253, I(2) = 12.6%). Furthermore, OR estimates in subgroup analyses were discussed, and strong associations were observed for dichlorodiphenyldichloroethylene (DDE, OR = 1.38, 95% CI 1.14 to 1.66), hexachlorocyclohexane (HCH, OR = 1.42, 95% CI 1.08 to 1.87), chlordane (OR = 1.93, 95% CI 1.51 to 2.48), and hexachlorobenzene (HCB, OR = 1.54, 95% CI 1.20 to 1.99). This meta-analysis had suggested that total OCPs of interest was significantly positively associated with NHL risk.

Chlorpyrifos Induces the Expression of the Epstein-Barr Virus Lytic Cycle Activator BZLF-1 via Reactive Oxygen Species

Organophosphate pesticides (OPs) are among the most widely used synthetic chemicals for the control of a wide variety of pests, and reactive oxygen species (ROS) caused by OPs may be involved in the toxicity of various pesticides. Previous studies have demonstrated that a reactivation of latent Epstein-Barr virus (EBV) could be induced by oxidative stress. In this study, we investigated whether OPs could reactivate EBV through ROS accumulation. The Raji cells were treated with chlorpyrifos (CPF), one of the most commonly used OPs. Oxidative stress indicators and the expression of the EBV immediate-early gene BZLF-1 were determined after CPF treatment. Our results show that CPF induces oxidative stress as evidenced by decreased malondialdehyde (MDA) level, accompanied by an increase in ROS production, DNA damage, glutathione (GSH) level, and superoxide dismutase (SOD) and catalase (CAT) activity. Moreover, CPF treatment significantly enhances the expression of BZLF-1, and the increased BZLF-1 expression was ameliorated by N-acetylcysteine (NAC) incubation. These results suggest that OPs could contribute to the reactivation of the EBV lytic cycle through ROS induction, a process that may play an important role in the development of EBV-associated diseases.

Epstein-Barr virus antibodies and the risk of associated malignancies: review of the literature

Epstein-Barr virus (EBV), a ubiquitous herpes virus that infects 90% of humans by adulthood, is linked to the development of various cancers, including nasopharyngeal carcinoma, gastric cancer, Burkitt lymphoma, non-Hodgkin lymphoma (NHL), and Hodgkin lymphoma. We reviewed the literature published since 1980 regarding an association between antibodies against EBV proteins and the risk of EBV-associated malignancies. Immunoglobulin A antibody levels that are elevated before diagnosis have consistently been associated with the risk of nasopharyngeal carcinoma, and patients with Hodgkin lymphoma have significantly higher immunoglobulin G antibody levels than disease-free controls. However, the link between the immune response to EBV and other EBV-associated malignancies was less clear. Although evidence of an association between the risk of Burkitt lymphoma and immunoglobulin G antibodies was consistent for available studies, the sample sizes were limited. Evidence for a link between antibodies against EBV and risk of either gastric cancer or NHL was inconsistent. Future investigations should account for tumor EBV status because only 7%-10% of gastric tumors and select NHL subtypes are related to EBV infection. Comparing differences in the associations between the humoral immune response to EBV and disease risk across cancers may help elucidate how this ubiquitous virus contributes to distinct tumors globally.

Epstein-Barr virus and risk of non-Hodgkin lymphoma in the cancer prevention study-II and a meta-analysis of serologic studies

Epstein-Barr virus (EBV) causes rare, malignant lymphomas. The role of EBV in other non-Hodgkin lymphomas (NHLs) remains unclear, but mildly reduced immune function could lead to reactivation of EBV and subsequent NHL. We examined the association between prospectively-collected plasma EBV antibodies and NHL risk in the Cancer Prevention Study-II (CPS-II) Nutrition Cohort and conducted a meta-analysis of our and published results. The CPS-II study included 225 NHL cases and 2:1 matched controls. No associations were observed between EBV serostatus or antibody levels and risk of NHL overall. However, when including only the three most common types of NHL (diffuse large B-cell lymphoma, follicular lymphoma, chronic lymphocytic leukemia/small lymphocytic lymphoma), high compared to low early antigen (EA-D) diffuse and BZLF1-encoded replication activator antibodies were associated with approximately 60% higher risk of NHL. Odds ratios (ORs) for EBV nuclear antigen-1 and viral capsid antigen (VCA)-p18 were elevated but not statistically significant. In the meta-analysis, both EA (summary OR = 1.52, 95% confidence interval (CI): 1.16-2.00) and VCA (summary OR = 1.20, 95% CI: 1.00-1.44) were positively associated with NHL risk. These results suggest EBV may be associated with a wider spectrum of NHL subtypes, but further study is needed to confirm and fully understand these associations.

Polychlorinated biphenyls and cancer: an epidemiological assessment

Polychlorinated biphenyls (PCBs) are toxic and persistent chemicals produced between 1930s and 1980s primarily for insulating fluids in heavy-duty electrical equipment in power plants, industries, and large buildings. They persist in the environment and accumulate in plants and animals, and have been classified as probable carcinogens to humans. We performed a systematic review and meta-analysis of scientific literature on the relationship between PCB exposure and human cancer. Two cohorts of people highly exposed to PCBs through ingestion of contaminated rice oil and some cohorts of occupationally exposed workers failed to show a definite increase in total cancer mortality and provided inconsistent results regarding single cancers. Several cohort and case-control studies investigated the association between PCBs and specific cancers, showing an association between PCB serum levels and non-Hodgkin lymphomas (NHL), with a summary odds ratio of 1.5 (95% confidence interval: 1.1-1.7), but no consistent results for the other cancer sites and types. In conclusion, this review provides some evidence for the role of PCBs in the development of NHL, although the inconsistent results of studies performed on highly polluted people and occupationally exposed workers do not allow a firm conclusion to be drawn.

Current status of the epidemiologic evidence linking polychlorinated biphenyls and non-hodgkin lymphoma, and the role of immune dysregulation

BACKGROUND

Although case-control studies conducted to date have largely affirmed the relationship between polychlorinated biphenyls (PCBs) and non-Hodgkin lymphoma (NHL), occupational cohort studies of PCB-exposed workers have been generally interpreted as negative, thereby raising doubts about a potential causal association. A common theme of immune dysregulation unifies many of NHL's strongest risk factors, and several authors have posited that subclinical immune dysregulation may increase NHL risk by decreasing host resistance, reducing control of cellular proliferation and differentiation, and diminishing tumor surveillance mechanisms.

OBJECTIVES

The goals of this review were a) to evaluate the epidemiological research examining the association between PCB exposure and NHL and discuss the contribution to the weight of evidence of case-control studies and occupational cohort studies; and b) to summarize the evidence for immune dysregulation as a means by which PCBs may cause NHL.

METHODS

We performed a literature search using PubMed and seven additional online biomedical and toxicological referencing libraries to identify literature published through August 2011.

DISCUSSION AND CONCLUSIONS

Overall, we conclude that the weight of evidence supports a causal role of PCBs in lymphomagenesis. The strongest epidemiological evidence for the relationship between PCBs and NHL comes from case-control studies conducted among the general population. Epidemiological and toxicological data demonstrating immunosuppressive and inflammatory effects of PCBs further contribute to the weight of evidence by providing a plausible explanation for how PCBs can cause NHL through immune dysregulation.

Plasma levels of polychlorinated biphenyls, non-Hodgkin lymphoma, and causation

Polychlorinated biphenyls (PCBs) are synthetic chlorinated hydrocarbons that have extensively polluted the environment and bioaccumulated in the food chain. PCBs have been deemed to be probable carcinogens by the Environmental Protection Agency, and exposure to high levels of PCBs has been consistently linked to increased risk of non-Hodgkin lymphoma (NHL). In the present article we present a forensic epidemiologic evaluation of the causal relationship between NHL and elevated PCB levels via application of the Bradford-Hill criteria. Included in the evaluation is a meta-analysis of the results of previously published case-control studies in order to assess the strength of association between NHL and PCBs, resulting in an odds ratio in which the lowest percentile PCB concentration (quartile, quintile, or tertile) has been compared with the highest percentile concentration in the study groups. The weight-adjusted odds ratio for all PCB congeners was 1.43 with a 95% confidence interval of 1.31 to 1.55, indicating a statistically significant causal association with NHL. Because of the lack of an unexposed comparison group, a rationale for the use of a less than 2.0 relative risk causal contribution threshold is presented herein, including an ecologic analysis of NHL incidence and PCB accumulation (as measured by sales volume) over time. The overall results presented here indicate a strong general causal association between NHL and PCB exposure.

A prospective study of organochlorines in adipose tissue and risk of non‑Hodgkin lymphoma

BACKGROUND

Exposure to organochlorines has been examined as a potential risk factor for non-Hodgkin lymphoma (NHL), with inconsistent results that may be related to limited statistical power or to imprecise exposure measurements.

OBJECTIVE

Our purpose was to examine associations between organochlorine concentrations in prediagnostic adipose tissue samples and the risk of NHL.

METHODS

We conducted a case–cohort study using a prospective Danish cohort of 57,053 persons enrolled between 1993 and 1997. Within the cohort we identified 256 persons diagnosed with NHL in the population-based nationwide Danish Cancer Registry and randomly selected 256 subcohort persons. We measured concentrations of 8 pesticides and 10 polychlorinated biphenyl (PCB) congeners in adipose tissue collected upon enrollment. Associations between the 18 organochlorines and NHL were analyzed in Cox regression models, adjusting for body mass index.

RESULTS

Incidence rate ratios and confidence intervals (CIs) for interquartile range increases in concentrations of dichlorodiphenyltrichlorethane (DDT), cis-nonachlor, and oxychlordane were 1.35 (95% CI: 1.10, 1.66), 1.13 (95% CI: 0.94, 1.36), and 1.11 (95% CI: 0.89, 1.38), respectively, with monotonic dose–response trends for DDT and cis-nonachlor based on categorical models. The relative risk estimates were higher for men than for women. In contrast, no clear association was found between NHL and PCBs.

CONCLUSION

We found a higher risk of NHL in association with higher adipose tissue levels of DDT, cis-nonachlor, and oxychlordane, but no association with PCBs. This is the first study of organochlorines and NHL using prediagnostic adipose tissue samples in the exposure assessment and provides new environmental health evidence that these organochlorines contribute to NHL risk.

Epstein-Barr virus serologic abnormalities and risk of rheumatoid arthritis among women

BACKGROUND

Epstein-Barr virus (EBV) infection and the immune response may be involved in the pathogenesis of rheumatoid arthritis (RA). Past studies have suggested an association between EBV and RA.

METHODS

We studied the association between EBV serologies and RA risk in a nested case-control study in the Nurses' Health Study (NHS) cohorts. We confirmed incident RA cases from 1990 to 2002 by questionnaire and medical record review. Each incident case with blood collected prior to RA symptoms was matched with a healthy participant by time of day and date of blood collection, birth year, menopausal status and postmenopausal hormone use. Immunofluorescence assays measured serologic EBV responses: viral capsid antigen, early-antigen-diffuse and early antigen-complex (restricted and diffuse), Epstein Barr nuclear antigen (EBNA)-1, EBNA-2 and cytomegalovirus (CMV), as control. All were reported as titers, except CMV, which was reported as positive or negative. Antinuclear antibody positive samples were excluded. Elevated EBV antibody titers were defined as the upper 20% (or nearest titer) among controls. Conditional logistic regression analyses modeled RA risk associated with elevated EBV titers or the presence/absence of CMV, further adjusted for pack-years smoking and alcohol intake.

RESULTS

Eighty-seven incident RA cases were identified. Mean time to RA after blood draw was 6.2 (± 3.5) years in NHS and 1.9 (± 0.6) years in NHS II. Antibody titers against EBV were not significantly different between pre-RA cases and controls.

CONCLUSIONS

In this prospective study of women, we observed no association between EBV serologies and RA risk.

Polychlorinated biphenyls and non-Hodgkin's lymphoma: a case-control study in Northern Italy

BACKGROUND

Polychlorinated biphenyls (PCBs) have been hypothesized to increase the risk of non-Hodgkin lymphoma (NHL), although conclusive evidence is still lacking. High levels of PCBs were found in soil in some areas close to a PCB-producing factory in Brescia, North Italy. We conducted a population-based case-control study among residents of the town to investigate the possible association between PCB pollution and NHL in this area.

METHODS

We included both incident and deceased NHL cases, and a random sample of the town residents as controls, frequency matched to cases as regards age and gender. Exposure to PCBs was estimated on the basis of the lifetime residential history of cases and controls in four different areas of the town-A, B and C (polluted areas) and D (control area).

RESULTS

A total of 495 cases (287 incident cases) and 1467 controls were enrolled. Positive associations were found between NHL and having resided for at least 10 years in the area A, the most polluted area (odds ratio, OR=1.8; p=0.02) and for having resided in any of the polluted areas considered together (A+B+C) (OR=1.4; p=0.08). However, no associations were evident for having resided 20 years or longer in the polluted areas or when analyzing the association with each subject's main residence in his/her lifetime.

CONCLUSION

This study provides some evidence for an association between PCB exposure and NHL, though results should be considered with caution in the absence of individual biological measures of exposure.

Halogenated flame retardants: do the fire safety benefits justify the risks?

Since the 1970s, an increasing number of regulations have expanded the use of brominated and chlorinated flame retardants. Many of these chemicals are now recognized as global contaminants and are associated with adverse health effects in animals and humans, including endocrine and thyroid disruption, immunotoxicity, reproductive toxicity, cancer, and adverse effects on fetal and child development and neurologic function. Some flame retardants such as polybrominated diphenyl ethers (PBDEs) have been banned or voluntarily phased out by manufacturers because of their environmental persistence and toxicity, only to be replaced by other organohalogens of unknown toxicity. Despite restrictions on further production in some countries, consumer products previously treated with banned retardants are still in use and continue to release toxic chemicals into the environment, and the worldwide use of organohalogen retardants continues to increase. This paper examines major uses and known toxic effects of commonly-used organohalogen flame retardants, replacements for those that have been phased out, their combustion by-products, and their effectiveness at reducing fire hazard. Policy and other solutions to maintain fire safety while reducing toxicity are suggested. The major conclusions are: (1) Flammability regulations can cause greater adverse environmental and health impacts than fire safety benefits. (2) The current options for end-of-life disposal of products treated with organohalogens retardants are problematic. (3) Life-cycle analyses evaluating benefits and risks should consider the health and environmental effects of the chemicals, as well as their fire safety impacts. (4) Most fire deaths and most fire injuries result from inhaling carbon monoxide, irritant gases, and soot. The incorporation of organohalogens can increase the yield of these toxic by-products during combustion. (5) Fire-safe cigarettes, fire-safe candles, child-resistant lighters, sprinklers, and smoke detectors can prevent fires without the potential adverse effects of flame retardant chemicals. (6) Alternatives to organohalogen flame retardant chemicals include using less flammable materials, design changes, and safer chemicals. To date, before evaluating their health and environmental impacts, many flame retardant chemicals have been produced and used, resulting in high levels of human exposure. As a growing literature continues to find adverse impacts from such chemicals, a more systematic approach to their regulation is needed. Before implementing new flammability standards, decision-makers should evaluate the potential fire safety benefit versus the health and environmental impacts of the chemicals, materials, or technologies likely to be used to meet the standard. Reducing the use of toxic or untested flame retardant chemicals in consumer products can protect human and animal health and the global environment without compromising fire safety.

Time trends of persistent organic pollutants in Sweden during 1993-2007 and relation to age, gender, body mass index, breast-feeding and parity

BACKGROUND

Persistent organic pollutants (POPs) are lipophilic chemicals that bioaccumulate. Most of them were resticted or banned in the 1970s and 1980s to protect human health and the environment. The main source for humans is dietary intake of dairy products, meat and fish. Little data exist on changes of the concentration of POPs in the Swedish population over time.

OBJECTIVE

To study if the concentrations of polychlorinated biphenyls (PCBs), DDE, hexachlorobenzene (HCB) and chlordanes have changed in the Swedish population during 1993-2007, and certain factors that may influence the concentrations.

METHODS

During 1993-2007 samples from 537 controls in different human cancer studies were collected and analysed. Background information such as body mass index, breast-feeding and parity was assessed by questionaires. Wilcoxon rank-sum test was used to analyse the explanatory factors specimen (blood or adipose tissue), gender, BMI, total breast-feeding and parity in relation to POPs. Time trends for POPs were analysed using linear regression analysis, adjusted for specimen, gender, BMI and age.

RESULTS

The concentration decreased for all POPs during 1993-2007. The annual change was statistically significant for the sum of PCBs -7.2%, HCB -8.8%, DDE -13.5% and the sum of chlordanes -10.3%. BMI and age were determinants of the concentrations. Cumulative breast-feeding >8 months gave statistically significantly lower concentrations for the sum of PCBs, DDE and the sum of chlordanes. Parity with >2 children yielded statistically significantly lower sum of PCBs.

CONCLUSIONS

All the studied POPs decreased during the time period, probably due to restrictions of their use.

Age-period-cohort modelling of non-Hodgkin's lymphoma incidence in a French region: a period effect compatible with an environmental exposure

BACKGROUND

The incidence of non-Hodgkin's lymphoma (NHL) has risen steadily during the last few decades in all geographic regions covered by cancer registration for reasons that remain unknown. The aims of this study were to assess the relative contributions of age, period and cohort effects to NHL incidence patterns and therefore to provide clues to explain the increasing incidence.

METHODS

Population and NHL incidence data were provided for the Doubs region (France) during the 1980-2005 period. NHL counts and person-years were tabulated into one-year classes by age (from 20 to 89) and calendar time period. Age-period-cohort models with parametric smooth functions (natural splines) were fitted to the data by assuming a Poisson distribution for the observed number of NHL cases.

RESULTS

The age-standardised incidence rate increased from 4.7 in 1980 to 11.9 per 100,000 person-years at risk in 1992 (corresponding to a 2.5-fold increase) and stabilised afterwards (11.1 per 100,000 in 2005). Age effects showed a steadily increasing slope up to the age of 80 and levelled off for older ages. Large period curvature effects, both adjusted for cohort effects and non-adjusted (p < 10-4 and p < 10-5, respectively), showed departure from linear periodic trends; period effects jumped markedly in 1983 and stabilised in 1992 after a 2.4-fold increase (compared to the 1980 period). In both the age-period-cohort model and the age-cohort model, cohort curvature effects were not statistically significant (p = 0.46 and p = 0.08, respectively).

CONCLUSIONS

The increased NHL incidence in the Doubs region is mostly dependent on factors associated with age and calendar periods instead of cohorts. We found evidence for a levelling off in both incidence rates and period effects beginning in 1992. It is unlikely that the changes in classification (which occurred after 1995) and the improvements of diagnostic accuracy could largely account for the 1983-1992 period-effect increase, giving way to an increased exposure to widely distributed risk factors including persistent organic pollutants and pesticides. Continued NHL incidence and careful analysis of period effects are of utmost importance to elucidate the enigmatic epidemiology of NHL.

A prospective study of Epstein-Barr virus antibodies and risk of non-Hodgkin lymphoma

Severe immunosuppression is an established risk factor for non-Hodgkin lymphoma (NHL), but an association with subclinical immune dysfunction is unclear. We conducted a case-control study nested in the Physicians' Health Study and the Nurses' Health Study cohorts to determine whether patterns of antibody response to Epstein-Barr virus (EBV) were associated with NHL risk. We measured antibody titers against viral capsid antigen, early antigen, and Epstein-Barr nuclear antigen (EBNA-1 and EBNA-2) in blood samples collected before diagnosis from 340 cases and 662 matched controls. Using conditional logistic regression, we estimated rate ratios (RRs) and 95% confidence intervals (CIs) for elevated versus normal titers and the ratio of anti-EBNA-1 to anti-EBNA-2 titers (≤ 1.0 vs > 1.0). We found no association between EBV serostatus, elevated titers, or an EBNA-1/EBNA-2 ratio ≤ 1.0 and NHL risk overall. For chronic lymphocytic leukemia/small lymphocytic lymphoma, suggestive associations were noted for elevated anti-EBNA-2 (RR, 1.74; 95% CI, 0.99-3.05), anti-viral capsid antigen (RR, 1.58; 95% CI, 0.79-3.14), and EBNA-1/EBNA-2 ratio ≤ 1.0 (RR, 1.52; 95% CI, 0.91-2.55). There was no evidence of heterogeneity by subtype. Overall, we found no evidence that EBV antibody profile predicts NHL risk in immunocompetent persons, with the possible exception of chronic lymphocytic leukemia/small lymphocytic lymphoma.

Plasma organochlorine levels and risk of non-Hodgkin lymphoma in the Nurses' Health Study

Numerous studies have reported positive associations of environmental exposure to polychlorinated biphenyls (PCB) and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) with the risk of non-Hodgkin lymphoma (NHL). In a case-control study nested within the Nurses' Health Study, a prospective cohort of U.S. women, we measured concentrations of PCBs and p,p'-DDE in blood samples from 145 women diagnosed with NHL at least 6 months after blood draw and 290 age- and race-matched controls. We used conditional logistic regression to estimate the odds ratios and 95% confidence intervals for each quartile of exposure relative to the lowest quartile. We also evaluated these associations for major histologic subtypes of NHL. There was no consistent evidence of an association of p,p'-DDE, total PCBs, immunotoxic, or individual PCB congeners with risk of NHL. These results do not support the hypothesis of a positive association between PCB exposure and development of NHL.

Plasma organochlorine levels and risk of non-Hodgkin lymphoma in a cohort of men

BACKGROUND

Environmental exposure to polychlorinated biphenyls (PCBs) and p,p'-dichlorodiphenyldichloroethylene (p, p'-DDE) has been associated with the risk of non-Hodgkin lymphoma.

METHODS

We conducted a case-control study nested within the Physicians' Health Study, a prospective cohort established in 1982. We measured concentrations of PCBs and p,p'-DDE in baseline blood samples from 205 men later diagnosed with non-Hodgkin lymphoma and 409 age- and race-matched controls. Lipid-adjusted organochlorine concentrations were categorized into quintiles based on the distribution among controls. We used conditional logistic regression to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) for each quintile relative to the lowest quintile. We also evaluated these associations for major histologic subtypes of non-Hodgkin lymphoma.

RESULTS

The risk of non-Hodgkin lymphoma was positively associated with the sum of 51 PCB congeners assayed (SigmaPCB); the group of immunotoxic congeners; the individual congeners 118, 138, 153, and 180; and the sum of these 4 congeners. The simple OR for the highest quintile of lipid-adjusted SigmaPCB versus the lowest was 1.9 (95% CI = 1.1-3.2; test for trend, P = 0.001), with similar trends for individual congeners and groups defined as above. Adjustment for height, body mass index, alcohol intake, smoking, and fish intake did not substantially change the effect estimates. No association was observed for p,p'-DDE. There was no evidence of statistical heterogeneity in effects by histologic subtype of lymphoma; however, this analysis was underpowered.

CONCLUSIONS

These results support the hypothesis of a positive association between PCB exposure and development of NHL in men.

Pesticides, soft-tissue sarcoma and non-Hodgkin lymphoma--historical aspects on the precautionary principle in cancer prevention

BACKGROUND

After the 2(nd) World War a long range of chemical agents have been introduced on the market, both in Sweden and most other countries. From the 1950's several pesticides gained increasing use in agriculture and forestry. In the 1970's public concern increased in Sweden especially regarding use of phenoxy herbicides to combat deciduous wood, although statements from different authorities were reassuring of the safety.

MATERIALS AND METHODS

At the end of the 1970's the author and his colleagues published the first scientific evidence of an association between exposure to phenoxyacetic acids, chlorophenols and certain malignant tumours, i.e., soft-tissue sarcoma and malignant lymphoma. The study subjects were also exposed to contaminating dioxins such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Later studies showed also an association between certain persistent organic pollutants such as polychlorinated biphenyls and non-Hodgkin lymphoma (NHL) with an interaction with titers of antibodies to Epstein-Barr virus early antigen. These results have been corroborated in other studies.

DISCUSSION

Over the years industry and its allied experts have attacked our studies, but in 1997 IARC classified TCDD as a human carcinogen, Group I. The increasing incidence of NHL in Sweden levelled off about 1990. The author postulated that the regulation or ban of the use of chlorophenols, certain phenoxy herbicides and some persistent organic pollutants in Sweden back in the 1970s has contributed to the now decreasing incidence of NHL. Unfounded criticism from industry experts may prohibit the precautionary principle and early warnings of cancer risk can be ignored. Cancer risks by certain chlorinated phenols may serve as a model of how the precautionary principle should be used by taking early warnings seriously.

Polybrominated diphenyl ethers in marine ecosystems of the American continents: foresight from current knowledge

Polybrominated diphenyl ethers (PBDEs) are a class of synthetic halogenated organic compounds used in commercial and household products, such as textiles, furniture, and electronics, to increase their flame ignition resistance and to meet fire safety standards. The demonstrated persistence, bioaccumulation, and toxic potential of these compounds in animals and in humans are of increasing concern. The oceans are considered global sinks for PBDEs, as higher levels are found in marine organisms than in terrestrial biota. For the past three decades, North America has dominated the world market demand for PBDEs, consuming 95% of the penta-BDE formulation. Accordingly, the PBDE concentrations in marine biota and people from North America are the highest in the world and are increasing. Despite recent restrictions on penta- and octa-BDE commercial formulations, penta-BDE containing products will remain a reservoir for PBDE release for years to come, and the deca-BDE formulation is still in high-volume use. In this paper, we review all available data on the occurrence and trends of PBDEs in the marine ecosystems (air, water, sediments, invertebrates, fish, seabirds, and marine mammals) of North and South America. We outline here our concerns about the potential future impacts of large existing stores of banned PBDEs in consumer products, and the vast and growing reservoirs of deca-BDE as well as new and naturally occurring brominated compounds on marine ecosystems.

PBDEs in US and German clothes dryer lint: a potential source of indoor contamination and exposure

Polybrominated diphenyl ethers (PBDEs) are emerging persistent organic pollutants (POPs). Since the 1970s, PBDEs have been widely used as additive flame retardants in furniture and electronic equipment. Due to their wide use and persistent nature, these chemicals are found in the environment, human blood, breast milk and other tissues in increasing levels in recent decades. PBDEs are similar to polychlorinated biphenyls (PCBs) in structure and toxicity. However, unlike PCBs and PCDDs/PCDFs, the route of PBDE exposure is not almost exclusively through food. PBDE levels in US food are not markedly higher than in Europe, although US human blood and milk levels are an order of magnitude higher. For these reasons, other possible routes of PBDE exposure have been investigated to understand PBDE intake into humans. PBDE contaminated clothes dryer lint and household dust are indicators of indoor contamination and may be sources of human exposure through hand-to-mouth contact or dermal absorption. There are very few publications about PBDEs in US or European lint. Household dryer lint from 12 US and seven German homes were analyzed for PBDEs by gas chromatography coupled to high-resolution mass spectrometry. We found the median US total PBDE levels were more than 10 times higher than median German levels and the mean US levels were two times higher than mean German levels. The US levels ranged from 321 to 3073ngg(-1) (median: 803ngg(-1), mean: 1138ngg(-1)) and the German levels were from 330 to 2069ngg(-1) (median: 71ngg(-1), mean: 361ngg(-1)). PBDE contamination of lint was found in all samples; the source of the PBDEs may be from dryer electrical components and/or dust deposition onto clothing.

Agricultural pesticides and risk of childhood cancers

Agricultural pesticide applications have the potential for significant drift beyond the target spray area and may result in exposure to non-farming residents in surrounding communities. Using geographic information system (GIS) methods, 1778 childhood cancer cases and 1802 controls born in Texas between 1990 and 1998 were assigned probable agricultural pesticide exposure based on proximity of birth residence to crop fields. Multivariate modeling was used to estimate odds ratios and 95% confidence intervals for selected cancers. For most childhood cancers, we found no evidence of elevated risk associated with residential proximity at birth to cropland. There was an overall pattern of increased risk for germ-cell tumors but the odds ratios were based on few number of exposed cases. There was also some indication of increased risk for non-Hodgkin lymphoma (NHL) and Burkitt lymphoma, but point estimates were imprecise and not statistically significant. Previous studies have assessed pesticide exposure primarily based on parental occupational history or household use, while our focus was on agricultural pesticides and so may represent a different array of chemical agents occurring at lower doses.

Organochlorine exposure, immune gene variation, and risk of non-Hodgkin lymphoma

Organochlorine exposure was linked to non-Hodgkin lymphoma (NHL) risk. To determine whether this relation is modified by immune gene variation, we genotyped 61 polymorphisms in 36 immune genes in 1172 NHL cases and 982 controls from the National Cancer Institute-Surveillance, Epidemiology, and End Results (NCI-SEER) study. We examined 3 exposures with elevated risk in this study: PCB180 (plasma, dust measurements), the toxic equivalency quotient (an integrated functional measure of several organochlorines) in plasma, and alpha-chlordane (dust measurements, self-reported termiticide use). Plasma (100 cases, 100 controls) and dust (682 cases, 513 controls) levels were treated as natural log-transformed continuous variables. Unconditional logistic regression was used to calculate beta coefficients and odds ratios, stratified by genotype. Associations between all 3 exposures and NHL risk were limited to the same genotypes for IFNG (C-1615T) TT and IL4 (5'-UTR, Ex1-168C>T) CC. Associations between PCB180 in plasma and dust and NHL risk were limited to the same genotypes for IL16 (3'-UTR, Ex22+871A>G) AA, IL8 (T-251A) TT, and IL10 (A-1082G) AG/GG. This shows that the relation between organochlorine exposure and NHL risk may be modified by particular variants in immune genes and provides one of the first examples of a potential gene-environment interaction for NHL.

Effects of decabrominated diphenyl ether (DBDE) on developmental immunotoxicity in offspring mice

Decabrominated diphenyl ether (DBDE), a representative brominated flame retardant ubiquitous in the environment, is suspected of being hazardous to humans. We evaluated the developmental immunotoxicity of DBDE by an assay system using respiratory syncytial virus (RSV) infection in offspring mice. Pregnant mice were continuously exposed to DBDE (10, 100, 1000, or 10,000ppm) in the diet from gestation day 10 to weaning on postnatal day 21. Offspring mice born to these dams were intranasally infected with RSV. Virus titers in the lungs of RSV-infected offspring exposed perinatally to DBDE increased dose-dependently compared with the control. The level of interferon-γ in the bronchoalveolar lavage fluids and gene expression of the chemokine RANTES in the lungs were also significantly elevated in offspring mice exposed to DBDE. Histopathological analysis revealed that pneumonia in the lungs of offspring mice exposed to 10,000ppm of DBDE was exacerbated compared with the control. These results indicate that DBDE is a developmental immunotoxic agent.

Increased concentrations of certain persistent organic pollutants in subjects with self-reported electromagnetic hypersensitivity--a pilot study

Electromagnetic hypersensitivity (EHS) is used for a variety of subjective symptoms related to exposure to electromagnetic fields (EMF). The aim of this pilot study was to analyze the concentrations of certain persistent organic pollutants (POPs) in subjects with self-reported EHS. In total, 13 EHS subjects and 21 controls were included, all female. The concentration of several POPs was higher in EHS subjects than in controls. Lower concentrations were found for hexachlorobenzene and two types of chlordanes. The only significantly increased odds ratios (ORs) were found for polybrominated diphenyl ether (PBDE) #47 yielding OR=11.7, 95% confidence interval (CI)=1.45-94.7 and the chlordane metabolite MC6 with OR=11.2, 95% CI=1.18-106. The results were based on low numbers and must be interpreted with caution. This hypothesis generating study indicates the necessity of a larger investigation on this issue.

Overweight/obesity and cancer genesis: more than a biological link

The classical view according to which overweight/obesity is related to cancer considers adipose tissue as an active and metabolic "organ", acting through endocrine, autocrine and paracrine processes. Consequently, it has been hypothesized, that genesis and progression of cancer may be caused by different biological factors acting through diverse mechanisms including changes in the synthesis and bioavailability of sex hormones, insulin resistance, release of growth factors and/or proinflammatory cytokines and abnormal energetic disposal and expenditure. We have shown that overweight/obesity can be experimentally induced by benzo[a]pyrene, a universal well characterized chemical pollutant and that overweight/obesity may in fact be caused by several types of chemical pollutants. In this paper we propose that in addition to the above hypothetical biological mechanisms, adipose tissue acts as a reservoir for lipophilic, liposoluble environmental carcinogens, so that chemical pollution may in fact generate both overweight/obesity and cancer. More precisely, we propose that many carcinogens, be they mutagens or promotors can be stored in the adipose tissue, be released at convenient dose in the blood circulation and therefore target peripheral tissues to induce carcinogenesis. Such carcinogens mainly include organochlorine pesticides and PCBs. Their association with an increased risk of cancer seems to be demonstrated for breast and prostate carcinoma, as well as for lymphoma, not only in obese patients, but also in normal weight or even leaner patients suggesting that the adipose tissue may act as a reservoir for environmental carcinogens in obese as well as in non-obese patients.

Epstein-Barr virus infection and risk of lymphoma: immunoblot analysis of antibody responses against EBV-related proteins in a large series of lymphoma subjects and matched controls

Epstein-Barr Virus (EBV) is consistently associated with distinct lymphoproliferative malignancies and aberrant EBV antibody patterns are found in most EBV cancer patients. We evaluate the detection of an abnormal reactive serological pattern to EBV (ab_EBV) infection and the risk of lymphoma in a multicentric case-control study. Serum samples were collected at study entry from 1,085 incident lymphoma cases from Spain, France, Germany, Czech Republic, Italy and 1,153 age, sex and country matched controls. EBV immunoglobulin G (IgG) serostatus was evaluated through a peptide-based ELISA combining immunodominant epitopes of EBNA1 (BKRF1) and VCA-p18 (BFRF3). Further, immunoblot analysis was performed to evaluate distinct antibody diversity patterns to EBV early antigens (EA), besides EBNA1, VCA-p18, VCA-p40 (BdRF1) and Zebra (BZLF1). Patients with chronic active EBV infection and aberrant EBV activity were characterized as having an abnormal reactive pattern (ab_EBV). Ab_EBV was observed in 20.9% of 2,238 included subjects with an increased proportion of cases presenting ab_EBV as compared to the control population (23.9% vs. 18.0% p = 0.001). Ab_EBV positivity was a risk factor for all lymphomas combined (odds ratio [OR] = 1.42, 95% confidence interval [CI]=1.15-1.74), and specifically for chronic lymphocytic leukaemia (OR = 2.96, 95%CI = 2.22-3.95). Lower levels of ab_EBV were observed for follicular lymphoma (OR = 0.38, 95%CI = 0.15-0.98). EBV may be involved in a larger subset of lymphomas among clinically immunocompetent subjects than previously thought, probably explained by an underlying loss of immune control of EBV latent infection. Ab_EBV is a useful tool to explore EBV imbalances preceding or paralleling possible EBV associated oncogenic events.

The non-Hodgkin lymphomas: a review of the epidemiologic literature

The non-Hodgkin lymphomas (NHL) are a heterogeneous group of B-cell and T-cell neoplasms that arise primarily in the lymph nodes. NHL incidence rates in the US doubled between about 1970 and 1990, and stabilized during the 1990s. NHL accounts for approximately 3.4% of cancer deaths in the US. Although some of the observed patterns in NHL have been related to HIV/AIDS, these conditions cannot fully explain the magnitude of the changes; neither do changes in classification systems nor improved diagnostic capabilities. Studies of occupational and environmental exposures (e.g., pesticides, solvents) have produced no consistent pattern of significant positive associations. Inverse associations with ultraviolet radiation exposure and alcohol and fish intake, and positive associations with meat and saturated fat intake have been reported in several studies; additional studies are needed to confirm or refute these associations. Family history of NHL or other hematolympho-proliferative cancers and personal history of several autoimmune disorders are associated with increased risk of NHL, but are not likely to account for a large proportion of cases. HIV and other infectious agents, such as human herpesvirus 8 and Epstein-Barr, appear to be associated with differing types of NHL, such as some B-cell lymphomas. Future epidemiologic studies should evaluate associations by NHL type, enhance exposure information collected, and elucidate factors that may identify susceptible (or resistant) subpopulations because of genetic, immunologic or other characteristics. The extent to which the etiology of NHL types may differ is important to resolve in ongoing and future studies.

Polychlorinated Biphenyl Levels in Peripheral Blood and Non-Hodgkin's Lymphoma: A Report from Three Cohorts

The incidence of non-Hodgkin's lymphoma (NHL) unrelated to HIV infection has steadily increased over the past several decades and remains substantially unexplained. Limited evidence suggests that increased concentrations of polychlorinated biphenyls (PCB) measured in blood or fat tissue are associated with increased risk of NHL. Although PCB congeners vary in their biological activity, the relation between individual congeners and NHL risk has not been examined previously using prospectively collected biospecimens. We examined congener-specific associations in three prospective cohorts. Prediagnostic serum or plasma concentrations of selected PCB congeners were measured among NHL cases and controls from these cohorts: Janus (190 cases and 190 controls) in Norway and CLUE I (74 cases and 147 controls) and the Nurses' Health Study (30 cases and 78 controls) in the United States. All blood samples were collected in the 1970s or 1980s. We used logistic regression to calculate odds ratios (OR) and 95% confidence intervals (95% CI) for the relations between risk of NHL and lipid-corrected plasma or serum concentrations. Several congeners (i.e., 118, 138, and 153) that were present at higher levels and were moderately to highly correlated with each other showed exposure-response trends with risk of NHL in all three cohorts. These associations were observed primarily among subjects diagnosed closer to the date of blood collection in the two cohorts with sufficient cases to permit stratification by time. Among cases diagnosed within the median years of follow-up (16 years in Janus and 12 years in CLUE I), ORs and 95% CIs for increasing fourths of concentration of congener 118 relative to the lowest fourth were as follows: 2.4 (0.9-6.5), 4.9 (1.6-15.3), and 5.3 (1.5-18.8; P(trend) < 0.005) in Janus and 8.1 (1.0-68.9), 6.6 (0.7-59.0), and 13.0 (1.6-106.8; P(trend) < 0.05) in CLUE I. Similar patterns were seen for congeners 138 and 153 and for total PCBs. Limited evidence of exposure-response trends was also observed for several other congeners. The primary 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane metabolite, p,p'-DDE, was not significantly associated with NHL in most analyses but slightly to moderately confounded the PCB associations. The results from these three cohorts suggest that concentrations of certain PCBs in blood are associated with increased risk of NHL.

Analytical Methods of Biological Monitoring for Exposure to Pesticides: Recent Update

Extensive use of synthetic pesticides for agricultural and nonagricultural purposes began in the past 50 years. As a result of their wide and extensive application, exposure to hazardous pesticides is a concern to the general population and occupationally exposed persons. Robust methods are therefore needed for measuring markers of pesticide exposure. This article presents a review of the most recently published analytical methodologies and instrumentations developed for and applied to biological monitoring of exposure to pesticides of various classes. Most of the methods reviewed here are based on chromatography combined with mass spectrometry detection. This work clearly demonstrates that although gas chromatography still appears to be the most widely employed technique for pesticide analysis in various biological samples, recently a trend has been observed toward the use of liquid chromatography coupled with tandem mass spectrometry.

Polychlorinated biphenyls and non-Hodgkin lymphoma

Several epidemiologic studies suggest that polychlorinated biphenyl (PCB) levels measured in peripheral blood or adipose tissue are related to increased risk of non-Hodgkin lymphoma (NHL) and, therefore, may be at least partially responsible for the rising incidence of NHL unrelated to HIV infection in recent decades. Case-control studies that measured PCBs in blood, adipose tissue, or household carpet dust, at the time of diagnosis, have observed elevated NHL risk associated with concentrations of either total PCBs or of specific congeners. Similar associations have been found in a number of prospective cohorts. These associations do not seem to be due to confounding by other organochlorines or by other known NHL risk factors. These results support evidence of PCB carcinogenicity from animal studies. However, interpretation of the epidemiologic evidence is limited by the wide range in measurement precision across congeners and by the moderate to high correlation among many congeners. Occupational cohort studies provide very limited support for a relationship between PCBs and NHL. In conclusion, there is mounting evidence of a relationship between certain PCBs and risk of NHL, but important questions remain, especially regarding the magnitude, timing, and causality of that relationship.

Effects of organochlorine pesticides on interleukin secretion from lymphocytes

Organochlorine pesticides have been used worldwide primarily as insecticides. Due to their chemical stability, they often persist in the environment long after their use has ceased. In a previous study, we found that six organochlorine compounds (alpha-chlordane, gamma-chlordane, 4,4'-DDT, heptachlor, oxychlordane, and pentachlorophenol (PCP)), at concentrations of 5 microM, were able to significantly decrease the ability of highly purified human natural killer (NK) cells to lyse tumor cells after exposures, ranging from 1 hour to 6 days. However, if T cells were present with the NK cells (T/NK cells), loss of lytic function was seen only with oxychlordane and PCP. The purpose of the current study is to begin to investigate the mechanism by which T cells may be blocking the negative effects of some organochlorine compounds on NK cell function. Here, we investigated the hypothesis that T cells could produce significant levels of NK-stimulatory interleukin(s) (ILs), and that this may account for the decreased inhibition seen with organochlorine exposures when T cells were present. Secretion of four cytokines that have a demonstrated capacity to influence NK function, and/or are secreted by T cells, was measured (IL-2, IL-4, IL-10, IL-12). We measured both the baseline levels of ILs and the effects of organochlorine compound on IL secretion in T/NK cells. The results showed that baseline levels of the NK-stimulatory IL, IL-12, were 898 +/- 264 pg/mL at 24 hours and IL-10 levels were 564 +/- 337 pg/mL. In contrast, IL-2 levels were 14 +/- 10 pg/mL, and IL-4 levels were 3 +/- 2 pg/mL at 24 hours. The two compounds that retained their capacity to decrease NK lytic function in T/NK cells, oxychlordane (5 microM) and PCP (5 and 10 microM), were able to either decrease the secretion of NK-stimulatory ILs (IL-2, IL-12 and/or IL-10) and/or increase secretion of the NK-inhibitory cytokine, IL-4, at each length of exposure tested.

Family history of hematopoietic and non-hematopoietic malignancies and risk of non-Hodgkin lymphoma

BACKGROUND

Family history of hematopoietic malignancies has been linked to the risk of non-Hodgkin lymphoma (NHL). The relationship between family history of specific hematopoietic and non-hematopoietic malignancies and the risk of NHL and by NHL subtypes are unclear.

METHODS

We analyzed data from a population-based case-control study in Connecticut women. A total of 601 histologically confirmed NHL incident cases and 717 randomly selected controls were included in the study. Unconditional logistic regression was used to estimate the association between family cancer history and risk of NHL overall and by NHL subtypes.

RESULTS

Compared to women who reported to have no family history of any malignancies in first-degree relatives, those who reported to have a family history of lymphoma (OR = 2.2, 95%CI: 1.1-4.5) or leukemia (OR = 2.5, 95%CI: 1.2-5.2) had an increased risk of NHL. The risk was higher among women who had a sibling with lymphoma or leukemia than those who had parents with lymphoma or leukemia. Several non-hematopoietic malignancies in first-degree relatives, including cancer of the lung (OR = 1.7, 95%CI: 1.1-2.6) in first-degree relatives, stomach (OR = 2.2, 95%CI: 0.8-5.9) and pancreas (OR = 2.6, 95%CI: 0.9-7.1) in parents, as well as liver (OR = 5.0, 95%CI: 1.0-24.6), breast (OR = 2.2, 95%CI: 1.3-3.9), cervix (OR = 7.5, 95%CI: 0.9-64.9), and ovary (OR = 3.5, 95%CI: 1.1-11.5) in siblings were also associated with an increased risk of NHL.

CONCLUSIONS

The risk associated with a family history of malignancies in first degree-relatives appears to vary by type of first-degree relatives.

Organochlorines and risk of non-Hodgkin lymphoma

Organochlorine chemicals and polychlorinated biphenyls (PCBs) have been suspected as possible risk factors for non-Hodgkin lymphoma (NHL). We investigated PCBs and organochlorine pesticides and risk of NHL in a population-based case-control study in British Columbia, Canada. Congeners of PCBs (including dioxinlike congeners) and pesticides or pesticide metabolites were measured in plasma of 422 pretreatment cases and 460 control subjects. This is so far the largest study to examine organochlorines in plasma to date. Several dioxin-like PCB congeners were associated with increased risk of NHL, including dioxin-like PCB nos. 118 and 156 with odds ratios (OR) for the highest versus lowest quartile between 1.6 and 1.8. Several non-dioxin-like congeners also showed significant associations. The PCB congener with the strongest association was no. 180 with an OR for the highest versus the lowest quartile of 1.83 (95% confidence interval = 1.18-2.84). Six pesticide analytes also showed a significant association with NHL; beta-hexachlorocyclohexane, p,p'-DDE, hexachlorobenzene, mirex, oxychlordane and trans-nonachlor. The strongest association was found for oxychlordane, a metabolite of the pesticide chlordane (highest vs. lowest quartile OR = 2.68, 95% confidence interval = 1.69-4.24). Our results provide further evidence that organochlorines contribute to NHL risk.

Non-Hodgkin lymphoma and pesticide exposure: 25 years of research

Over the past 40 years, a substantial rise in the incidence of non-Hodgkin lymphoma (NHL) has been observed. Epidemiologic studies aimed at understanding this rise have revealed some association with occupational exposure. NHL is common among farmers, where pesticides have been described as the culprit. The association between pesticides and NHL has been demonstrated mainly in case-control studies, while retrospective cohorts have been less convincing. Pesticides including chlorphenol and phenoxyacetic acid herbicides, organochlorines, and organophosphate insecticides, carbamates, and fungicides have been associated with NHL. Although the causality has not been clearly proven, both genotoxic and nongenotoxic mechanisms for lymphomagenesis have been proposed. The leveling-off of NHL incidence in certain countries may be the result of a favorable change in pesticide usage patterns. Future studies, such as the Agricultural Health Study, may clarify the uncertainties regarding this issue.

Understanding population and individual risk assessment: the case of polychlorinated biphenyls

Decisions about how to improve or protect the public health can be, and sometimes necessarily are, made on imprecise science. The regulation of potential human carcinogens in the environment entails a population-risk assessment process intended to reduce risks to less than one additional cancer in 100,000 or 1,000,000 persons. These risk assessment processes, however, may be miscommunicated or misinterpreted in the context of individual cancer risks by scientists, regulators, the lay media, and the public. This commentary will review methods for establishing a causal relationship between carcinogen exposures and cancer risk. It will use the case of polychlorinated biphenyls (PCB) as an example of how to place scientific data into the context of human exposure and cancer risk. PCBs are widespread environmental contaminants and most people have detectable levels of PCBs in their bodies. The primary source for exposure in the general population is through the diet. PCBs are carcinogens in experimental animal models, but how this information can be extrapolated to human risk remains uncertain. PCB experimental studies provide data that are used to regulate and control human exposure, although the epidemiologic evidence fails to establish PCBs as human carcinogens. Thus, what is used for population-risk assessment may not be appropriate for individual-risk assessment or concluding that a causal relationship exists between PCB exposure and cancer risk. The hazards from a carcinogen designated by regulatory and review agencies as a "probable" human carcinogen is often misunderstood out of context about the magnitude of the risk and in what settings. How scientists communicate their results in scientific articles can strongly influence how others interpret their data. Misunderstandings from both the use of regulatory and review-agency opinions and the conclusions espoused by scientists occur in the media, among private physicians counseling their patients about cancer risk, and in the legal settings where plaintiffs seek compensation for exposure and alleged harm (or future harm). This can lead to false conclusions about what caused a cancer in a specific patient, undue anxiety about future cancer risk, inappropriate cancer screening, and attendant increased morbidity due to increased uses of the medical system and complication rates from medical procedures. The communication of research findings by scientists must be presented with caution, resisting the temptation to extrapolate, inappropriately, research data to the general population.

Mortality and exposure response among 14,458 electrical capacitor manufacturing workers exposed to polychlorinated biphenyls (PCBs)

BACKGROUND

We expanded an existing cohort of workers (n = 2,588) considered highly exposed to polychlorinated biphenyls (PCBs) at two capacitor manufacturing plants to include all workers with at least 90 days of potential PCB exposure during 1939-1977 (n = 14,458). Causes of death of a priori interest included liver and rectal cancers, previously reported for the original cohort, and non-Hodgkin lymphoma (NHL), melanoma, and breast, brain, intestine, stomach, and prostate cancers, based on other studies.

METHODS

We ascertained vital status of the workers through 1998, and cumulative PCB exposure was estimated using a new job exposure matrix. Analyses employed standardized mortality ratios (SMRs; U.S., state, and county referents) and Poisson regression modeling.

RESULTS

Mortality from NHL, melanoma, and rectal, breast, and brain cancers were neither in excess nor associated with cumulative exposure. Mortality was not elevated for liver cancer [21 deaths; SMR 0.89; 95% confidence interval (CI), 0.55-1.36], but increased with cumulative exposure (trend p-value = 0.071). Among men, stomach cancer mortality was elevated (24 deaths; SMR 1.53; 95% CI, 0.98-2.28) and increased with cumulative exposure (trend p-value = 0.039). Among women, intestinal cancer mortality was elevated (67 deaths; SMR 1.31; 95% CI, 1.02-1.66), especially in higher cumulative exposure categories, but without a clear trend. Prostate cancer mortality, which was not elevated (34 deaths; SMR 1.04; 95% CI, 0.72-1.45), increased with cumulative exposure (trend p-value = 0.0001).

CONCLUSIONS

This study corroborates previous studies showing increased liver cancer mortality, but we cannot clearly associate rectal, stomach, and intestinal cancers with PCB exposure. This is the first PCB cohort showing a strong exposure-response relationship for prostate cancer mortality.

Adipose Tissue Concentrations of Persistent Organic Pollutants and the Risk of Prostate Cancer

OBJECTIVE

We sought to study the concentrations of certain persistent organic pollutants with endocrine-disrupting properties in cases with prostate cancer and controls with benign prostate hyperplasia.

METHODS

Adipose tissue was obtained from 58 cases and 20 controls.

RESULTS

The median concentration among controls was used as cut-off in the statistical analysis. In the total material, a greater-than median concentration of PCB congener 153 yielded an odds ratio (OR) of 3.15 and 95% confidence interval (CI) of 1.04-9.54 and one chlordane type, trans-chlordane, yielded OR 3.49 (95% CI = 1.08-11.2). In the group of case subjects with PSA levels greater than the median level of 16.5 ng/mL, PCB 153 was OR 30.3 (95% CI = 3.24-284), hexachlorobenzene OR = 9.84 (95% CI = 1.99-48.5), trans-chlordane OR = 11.0 (95% CI = 1.87-64.9), and the chlordane-type MC6 OR = 7.58 (95% CI = 1.65-34.9). The grouping of PCBs according to structural and biological activity was found to produce significantly increased risks for enzyme and phenobarbital-inducing PCBs and lower chlorinated PCBs in the case group with PSA levels greater than 16.5 ng/mL.

CONCLUSIONS

These chemicals might be of etiologic significance but need to be further investigated. The biological relevance of the arbitrary cut-off point of PSA is unclear.

Update: cohort mortality study of workers highly exposed to polychlorinated biphenyls (PCBs) during the manufacture of electrical capacitors, 1940-1998

BACKGROUND

The National Institute for Occupational Safety and Health previously reported mortality for a cohort of workers considered highly exposed to polychlorinated biphenyls (PCBs) between 1939 and 1977 at two electrical capacitor manufacturing plants. The current study updated vital status, examined liver and rectal cancer mortality previously reported in excess in this cohort and evaluated mortality from non-Hodgkin's lymphoma (NHL) and cancers of the stomach, intestine, breast, prostate, skin (melanoma) and brain reported to be in excess in other cohort and case-control studies of PCB-exposed persons.

METHODS

Mortality was updated through 1998 for 2572 workers. Age-, gender-, race- and calendar year-adjusted standardized mortality ratios (SMRs) and 95% confidence intervals (CI) were calculated using U.S., state and county referent rates. SMRs using U.S. referent rates are reported. Duration of employment was used as a surrogate for exposure.

RESULTS

Consistent with the previous follow-up, mortality from biliary passage, liver and gall bladder cancer was significantly elevated (11 deaths, SMR 2.11, CI 1.05 - 3.77), but mortality from rectal cancer was not (6 deaths, SMR 1.47, CI 0.54 - 3.21). Among women, mortality from intestinal cancer (24 deaths, SMR 1.89, CI 1.21 - 2.82) and from "other diseases of the nervous system and sense organs", which include Parkinson's disease and amyotrophic lateral sclerosis, (15 deaths, SMR 2.07, CI 1.16 - 3.42) were elevated. There were four ALS deaths, all women (SMR 4.35, CI 1.19-11.14). Mortality was elevated for myeloma (7 deaths, SMR 2.11, CI 0.84 - 4.34), particularly among workers employed 10 years or more (5 deaths, SMR 2.80, CI 0.91 - 6.54). No linear associations between mortality and duration of employment were observed for the cancers of interest.

CONCLUSION

This update found that the earlier reported excess in this cohort for biliary, liver and gall bladder cancer persisted with longer follow-up. Excess mortality for intestinal cancer among women was elevated across categories of duration of employment; myeloma mortality was highest among those working 10 years or more. The small numbers of deaths from liver and intestinal cancers, myeloma and nervous system diseases coupled with the lack of an exposure-response relationship with duration of employment preclude drawing definitive conclusions regarding PCB exposure and these causes of death.

Residential Insecticide Use and Risk of Non-Hodgkin's Lymphoma

Previous studies have linked non-Hodgkin's lymphoma (NHL) with occupational exposure to insecticides, but residential use is largely unexplored. In this population-based case-control study, we examined NHL risk and use of insecticides in the home and garden. We identified NHL cases, uninfected with HIV, diagnosed between 1998 and 2000 among women and men ages 20 to 74 years in Iowa and the metropolitan areas of Los Angeles, Detroit, and Seattle. Controls were selected using random digit dialing or Medicare files. Computer-assisted personal interviews (1,321 cases and 1,057 controls) elicited data on insecticide use at each home occupied since 1970. Insecticide levels were measured in dust taken from used vacuum cleaner bags (682 cases and 513 controls). We previously reported a positive association with dichlorodiphenyldichloroethylene levels in carpet dust residues. Here, we focus on insecticides that were commonly used after 1970, the time period covered by our questionnaire. People whose homes were treated for termites had elevated NHL risk (odds ratio, 1.3; 95% confidence interval, 1.0-1.6). Risk was modestly, although not significantly, elevated in all but one study center and in all sexes and races. The elevation in risk was restricted to people whose homes were treated before the 1988 chlordane ban. There was a significant trend of increasing risk with increasing levels of alpha-chlordane residues in dust (P(trend) = 0.04) and a marginally significant trend for gamma-chlordane (P(trend) = 0.06). We found no evidence of associations for insects overall, for specific types of insects other than termites, or for elevated residues of other insecticides. We concluded that chlordane treatment of homes for termites may increase residents' NHL risk.

Polychlorinated biphenyls (PCBs): routes of exposure and effects on human health

The polychlorinated biphenyls (PCBs) are synthetic organochlorine chemicals that were useful industrial products in the past, but their production was ended because they persist in both the environment and living organisms. The PCBs are mixtures of up to 209 different components (congeners), depending on the number and position of chlorines around the biphenyl ring. The PCBs are fat-soluble substances to which everyone is exposed through ingesting animal fats, inhalation, or dermal contact. Exposure to PCBs suppresses the immune system, thereby increasing the risk of acquiring several human diseases. Both ortho-substituted and coplanar (dioxin-like) congeners are tumor promoters that enhance the effects of other carcinogenic substances. PCB exposure, especially during fetal and early life, reduces IQ and alters behavior. The PCBs alter thyroid and reproductive function in both males and females and increase the risk of developing cardiovascular and liver disease and diabetes. Women are at high risk of giving birth to infants of low birth weight, who are at high lifetime risk for several diseases. As knowledge of their toxic effects has grown faster than environmental levels have declined, PCBs remain dangerous contaminants.

Life-style and environmental factors in the development of nasal NK/T-cell lymphoma: A case–control study in East Asia

Cases of nasal NK/T-cell lymphoma (NKTCL) occur occasionally in Asian and Latin American countries but rarely in Western countries. The etiological role of life-style and environmental factors in nasal NKTCL was investigated. Five university hospitals in Japan and one each in Korea and China participated in this study; a total of 88 cases and 305 hospital controls were accrued during 2000-2005. The odds ratio (OR) of NKTCL obtained after adjustments of age, sex and country was 4.15 (95% confidence interval (CI), 1.74-9.87) for farmers, 2.81 (CI, 1.49-5.29) for producers of crops, 4.01 (CI, 1.99-8.09) for pesticide users, 11.65 (CI, 1.17-115.82) for residents near garbage burning plants, 2.95 (CI, 1.25-6.95) for former drinkers, and 0.49 (CI, 0.23-1.04) for current smokers. The ORs for crop producers, who minimized their exposure to pesticides by using gloves and glasses, and sprinkling downwind at the time of pesticide use, were 3.30 (95% CI, 1.28-8.54), 1.18 (95% CI, 0.11-12.13) and 2.20 (95% CI, 0.88-5.53), respectively, which were lower than those for producers who did not take these precautions. Exposure to pesticides and chemical solvents could be causative of NKTCL. Taken together, life-style and environmental factors might be risk factors for NKTCL.