Serum concentrations of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) and risk of primary liver cancer

Overview of the pesticide contamination provided by the last Brazilian water quality surveillance information system for human consumption (SISÁGUA 2022) report

The Water Quality Surveillance Information System for Human Consumption (SISÁGUA) is designed to manage the risks of water contamination for human consumption. This short communication focuses on data from the 2022 Report regarding pesticide analysis. The data centers on 27 active pesticide ingredients found in drinking water samples exceeding the maximum residual limits (MRLs) established by Brazilian legislation. Results indicate that 1609 municipalities (60 %) found at least one pesticide in their water. Two hundred ten municipalities detected all 27 pesticides tested, with 11 of these pesticides reported to have some carcinogenic potential. Nearly one and a half million people were exposed to levels above the Brazilian MRL, with the sum of maximum detected residues exceeding 80,000 ppb. Additionally, the report highlights that 53 % of Brazilian municipalities did not submit water monitoring data for human consumption. Thus, improving and expanding the scope of water analysis within the SISÁGUA framework is essential.

A new insight into the mechanism of dichlorodiphenyltrichloroethane-induced hepatotoxicity based on GSDME-mediated pyroptosis

There have been persistent concerns about the safety risks associated with DDT residues in the environment. Studies have shown that exposure to DDT or its metabolites can cause various liver diseases. However, the mechanisms of liver toxicity haven't been well studied. In our current investigation, we observed that DDT triggers pyroptosis in human liver cells (HL-7702), representing a novel form of programmed cell death. Our results delineated DDT (0-100 μM) induced pyroptosis in HL-7702 cells, which was confirmed through morphological changes, lactate dehydrogenase (LDH) release, gasdermin E (GSDME) cleavage and Annexin-V/PI staining. Knockdown of GSDME reduced cell death and transferred the mode of cell death from pyroptosis to apoptosis. Notably, DDT exposure markedly increased reactive oxygen species (ROS) production, concurrent with c-Jun N-terminal kinase (JNK) phosphorylation. Intervention with a ROS inhibitor or JNK inhibitor SP600125 restored cell viability and hindered GSDME-mediated pyroptosis. Our results firstly demonstrate that DDT suppresses HL-7702 cells growth by inducing pyroptosis mainly through the ROS/JNK/GSDME pathway. These findings not only contribute to an in-depth understanding of DDT toxicity but also open avenues for gaining valuable insights into potential mitigation strategies and therapeutic interventions.

Quercetin protects human liver cells from o,p'-DDT-induced toxicity by suppressing Nrf2 and NADPH oxidase-regulated ROS production

Epidemiologic studies have revealed that Dichlorodiphenyltrichloroethane (DDT) and its metabolites are associated with liver diseases. However, there has been little emphasis on the mechanism underlying liver toxicity of o,p'-DDT and relevant effective inhibitors investigation. This study indicated o,p'-DDT exposure significantly decreased cell viability and promoted lactate dehydrogenase (LDH) release based on the investigation of cytotoxicity by trypan blue exclusion counts, MTT, and lactate dehydrogenase (LDH) assays. Comet, micronuclei, and DNA-protein crosslinks (DPC) assays demonstrated o,p'-DDT exposure increased the comet parameters, micronuclei frequency, and DPC coefficient. Meanwhile, we found o,p'-DDT induced mitochondria-dependent apoptosis, which is characterized by the loss of of mitochondrial membrane potential (Δψm), decreased Bcl-2 expression, and increased protein levels of Bax, cytochrome c, activated-caspase-9, and activated-caspase-3. Furthermore, o,p'-DDT induced reactive oxygen species (ROS) overproduction, decreased the protein levels of nuclear factor erythroid-derived 2-like 2 (Nrf2) in the nuclear, and enhanced the expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. However, quercetin treatment significantly antagonized o,p'-DDT-induced cytotoxicity, genotoxicity, and apoptosis as well as effects on ROS, Nrf2, and NADPH oxidase. Taken together, these findings suggested quercetin could alleviate o,p'-DDT-induced toxicity in HL-7702 cells via inhibiting ROS production, which is modulated by down-regulating nuclear Nrf2 levels and NADPH oxidase expression.

A Common Feature of Pesticides: Oxidative Stress-The Role of Oxidative Stress in Pesticide-Induced Toxicity

Pesticides are important chemicals or biological agents that deter or kill pests. The use of pesticides has continued to increase as it is still considered the most effective method to reduce pests and increase crop growth. However, pesticides have other consequences, including potential toxicity to humans and wildlife. Pesticides have been associated with increased risk of cardiovascular disease, cancer, and birth defects. Labels on pesticides also suggest limiting exposure to these hazardous chemicals. Based on experimental evidence, various types of pesticides all seem to have a common effect, the induction of oxidative stress in different cell types and animal models. Pesticide-induced oxidative stress is caused by both reactive oxygen species (ROS) and reactive nitrogen species (RNS), which are associated with several diseases including cancer, inflammation, and cardiovascular and neurodegenerative diseases. ROS and RNS can activate at least five independent signaling pathways including mitochondrial-induced apoptosis. Limited in vitro studies also suggest that exogenous antioxidants can reduce or prevent the deleterious effects of pesticides.

Environmental Risk Factors Implicated in Liver Disease: A Mini-Review

Liver disease is a global health issue, resulting in about two million deaths per year. It encompasses a wide spectrum of varied or unknown etiologies, ranging from lifestyle choices to pre-existing comorbidities. In recent decades, exposure to environmental toxins and subsequent liver health outcomes have captured public interest, due to the extensive application of pesticides, consumption of aflatoxin contaminated foodstuff, and cyanobacterial harmful algae blooms in endemic regions of liver disease. Hepatocellular carcinoma is a serious and debilitating condition of the liver, characterized by abdominal pain and unexplained weight loss. Established risk factors for hepatocellular carcinoma include alcohol consumption, cigarette smoking, and viral infections of hepatitis B and C. However, mounting evidence suggests that environmental toxins may represent an important contributing factor in hepatocellular carcinoma development. This mini-review synthesizes epidemiological investigations, providing evidence for environmental toxins as one potential risk factor for liver disease.

New Trend in the Extraction of Pesticides from the Environmental and Food Samples Applying Microextraction Based Green Chemistry Scenario: A Review

This review focused on the green microextraction methods used for the extraction of pesticides from the environmental and food samples. Microextraction techniques have been explored and applied in various fields of analytical chemistry since its beginning, as evinced by the numerous reviews published. The success of any technique in science and technology is measured by the simplicity, environmentally friendly, and its applications; and the microextraction technique is highly successive. Deliberations were attentive to studies where efforts have been made to validate the methods through the inter-laboratory comparison study to assess the analytical performance of microextraction techniques against conventional methods. Succinctly, developed microextraction methods are shown to impart significant benefits over conventional techniques. Provided that the analytical community continues to put forward attention and resources into the growth and validation of the microextraction technique, a promising future for microextraction is forecasted.

Epidemiology of Non-Hodgkin's Lymphoma

Non-Hodgins’s lymphoma (NHL) is the most common hematological malignancy worldwide, accounting for nearly 3% of cancer diagnoses and deaths. NHL is the seventh most prevalent cancer and has the sixth highest mortality among cancers in the US. NHL accounts for 4% of US cancer diagnoses, and incidence has increased 168% since 1975 (while survival has improved 158%). NHL is more common among men, those >65 years old, and those with autoimmune disease or a family history of hematological malignancies. NHL is a heterogenous disease, with each subtype associated with different risk factors. Marginal zone lymphoma (MZL) is strongly associated with Sjogren’s syndrome (SS) and Hashimoto’s thyroiditis, while peripheral T-cell lymphoma (PTCL) is most associated with celiac disease. Occupational exposures among farm workers or painters increases the risk of most of the common subtypes. Prior radiation treatment, obesity, and smoking are most highly associated with diffuse large B-cell lymphoma (DLBCL), while breast implants have been rarely associated with anaplastic large cell lymphoma (ALCL). Infection with Epstein–Barr Virus (EBV) is strongly associated with endemic Burkitts lymphoma. HIV and human herpes virus 8 (HHV-8), is predisposed to several subtypes of DLBCL, and human T-cell lymphoma virus (HTLV-1) is a causative agent of T-cell lymphomas. Obesity and vitamin D deficiency worsen NHL survival. Atopic diseases and alcohol consumption seem to be protective against NHL.

Chemical Risk Factors of Primary Liver Cancer: An Update

Primary liver cancer has the sixth highest incidence and fourth highest cancer mortality worldwide. Hepatitis B is the leading cause of liver cancer, though its incidence is decreasing with vaccination. Alcohol is the leading cause of liver transplant, cirrhosis, and cancer in the developed world, and is projected to surpass hepatitis B as the leading hepatic cancer etiology worldwide. Tobacco smoking has shown a positive association with liver cancer in a majority of studies, though not all. Aflatoxin, a mycotoxin produced by Aspergillus, is estimated to account for 3–20% of global liver cancer cases, 40% of which occur in sub-Saharan Africa. These statistics are confounded by the prevalence of hepatitis B, which may have a synergistic effect on hepatic carcinogenesis. Aflatoxin is ingested and likely inhaled from agricultural products, placing farmers, food processors, and textile workers in developing nations at risk. Vinyl-chloride is used in the production of PVC plastics and causes rare liver angiosarcoma, hepatocellular carcinoma, and other neoplasms. Arsenic and cadmium are naturally-occurring, hepatocarcinogenic metals with high occupational exposure in industries involving coal, metals, plastics, and batteries. Millions of laborers in waste-disposal and manufacturing are exposed to organic solvents and N-nitrosamines, which vary from carcinogenic (group 1) to possibly carcinogenic (group 2B) in their IARC designation. Insecticide DDT is possibly hepatocarcinogenic (group 2B), though continues to be used for malaria control in the developing world. While suggested by case reports, anabolic steroids and oral contraceptives have not been shown to increase liver cancer risk in large studies.

Independent and Joint Associations between Serum Calcium, 25-Hydroxy Vitamin D, and the Risk of Primary Liver Cancer: A Prospective Nested Case-Control Study

BACKGROUND

Accumulating evidence has shown that serum calcium and vitamin D may be associated with or influence various cancer risks. However, no prospective studies have evaluated the independent and joint associations between prediagnostic levels of serum calcium and vitamin D and future risk of incident primary liver cancer.

METHODS

We used a nested case-control design to evaluate subjects over 22 years of follow-up. Serum calcium, 25-hydroxy vitamin D [25(OH)D], and three markers of hepatitis B virus and hepatitis C virus were measured in baseline serum from 226 incident primary liver cancer cases and 1,061 matched controls. We calculated ORs and 95% confidence intervals (CI) using logistic regression to estimate the associations between calcium, 25(OH)D, and primary liver cancer risk.

RESULTS

Multivariable adjusted models showed that subjects with both low (ORLow/Medium = 1.48, 95% CI = 1.01-2.17) or high (ORHigh/Medium = 1.92, 95% CI = 1.34-2.76) calcium had an increased primary liver cancer risk, while those with high 25(OH)D had a decreased risk of primary liver cancer (ORHigh/Medium = 0.54, 95% CI = 0.35-0.82). In joint analyses, when compared with subjects with medium calcium and 25(OH)D, subjects with high calcium and medium 25(OH)D had elevated odds of developing primary liver cancer (OR = 1.89, 95% CI = 1.17-3.05); those with medium calcium and high 25(OH)D had reduced odds of developing primary liver cancer (OR = 0.34, 95% CI = 0.17-0.67); and subjects in other classifications of calcium and serum 25(OH)D levels had no change in the odds of developing primary liver cancer (all P > 0.05).

CONCLUSIONS

In a nutrient-deficient population, we found that serum calcium and serum 25(OH)D could potentially be modifiable risk or protective factors.

IMPACT

Our findings provide potential targets for primary liver cancer prevention and control.

Gene-environment interactions between GSTs polymorphisms and targeted epigenetic alterations in hepatocellular carcinoma following organochlorine pesticides (OCPs) exposure

Exposure to environmental pollutant organochlorine pesticides (OCPs) and the role of tumour suppressor GSTs gene polymorphisms as well as epigenetic alterations have all been well reported in hepatocarcinogenesis. However, the interplay between environmental risk factors and polymorphic tumour suppressor genes or epigenetic factors in hepatocellular carcinoma (HCC) development remains ambiguous. Herein, we investigated the relationship of three GSTs polymorphisms (GSTT1 deletion, GSTM1 deletion, GSTP1 rs1695) as well as GSTP1 promoter region DNA methylation and HCC risk with a particular focus on the interaction with OCPs exposure among 90 HCC cases and 99 controls in a Chinese population. Serum samples were analysed for OCPs exposure employing gas chromatography coupled with mass selective detector (GC-MS). GSTs polymorphisms and epigenetic alterations were determined using high-resolution melting PCR (HRM PCR) and DNA sequencing. After adjusting for confounders (HBV infection, smoking, alcohol consumption, BMI, age, gender), OCPs exposure and GSTP1 methylation is significantly associated with elevated risk of HCC, while no significance is observed for GSTs polymorphisms. Moreover, the effects of OCPs exposure on HCC risk are more pronounced amongst GSTP1 (Ile/Val + Val/Val) and GSTP1 promoter methylation subjects than those who were GSTP1 (Ile/Ile) and unmethylated subjects. The interactions between OCPs exposure and GSTP1 genotype as well as GSTP1 epigenetic status are statistically significant. The current study demonstrates the importance of gene-environment interactions in the multifactorial development of HCC.

EASL Clinical Practice Guideline: Occupational liver diseases

A variety of chemicals have been linked to occupational liver diseases, including several solvents and mixtures thereof, pesticides, and metals. Workplace exposures have been associated with virtually the entire spectrum of acute and chronic liver diseases. However, their prevalence is inadequately quantified and their epidemiology limited. Occupational liver diseases may result from high accidental or from prolonged lower level exposures. Whereas the former is uncommon and easily recognised, the latter are relatively more frequent but often overlooked because they may display normal values of conventional markers, have an insidious onset and be asymptomatic or be obfuscated and confounded by concurrent conditions. In addition, specific tests of toxicity are not available, histopathology may not be revealing and the assessment of internal dose of chemicals is usually not decisive. Given these circumstances, the diagnosis of these liver disorders is challenging, one of exclusion and often requires an interdisciplinary approach. These recommendations offer a classification of the type of liver injuries associated with occupational exposures - based in part on the criteria for drug-induced liver injury - a grading of their severity, and the diagnostic and preventive criteria for chemically induced occupational liver disease.

Prediagnostic serum organochlorine insecticide concentrations and primary liver cancer: A case-control study nested within two prospective cohorts

Although experimental evidence indicates that certain organochlorine insecticides are hepatocarcinogens, epidemiologic evidence for most of these chemicals is very limited. We estimated associations, using prospectively collected sera, between organochlorine insecticide concentrations and cancer registry-identified primary liver cancer in two cohorts, one from the United States and one from Norway. In nested case-control studies, we used sera collected in the 1960s-1980s from 136 cases and 408 matched controls from the Kaiser Permanente Northern California Multiphasic Health Checkup (MHC) cohort and 84 cases and 252 matched controls from the population-based Norwegian Janus cohort. We measured concentrations of nine organochlorine insecticides/metabolites and markers of hepatitis B and C in sera. Adjusted odds ratios (OR) and 95% confidence intervals (CI) for tertiles of lipid-corrected organochlorines were calculated for each cohort using conditional logistic regression. Among MHC participants with sera from the 1960s, there was a suggestive exposure-response trend for trans-nonachlor (second and third tertile of analyte ORs = 1.63 and 1.95, respectively; p-trend = 0.08) and a nonsignificantly elevated risk for the highest tertile of oxychlordane (OR = 1.87). Among Janus participants with sera from the 1970s, we observed an apparent trend for p,p'-DDT (second and third tertile ORs = 1.70 and 2.14, respectively; p-trend = 0.15). We observed little consistency in patterns of association between the cohorts. We found limited evidence that exposure to p,p'-DDT and chlordane-related oxychlordane and trans-nonachlor may be associated with increased risk of primary liver cancer. However, the modest strength of these associations and their lack of concordance between cohorts necessitate caution in their interpretation.

Association of tooth loss with liver cancer incidence and chronic liver disease mortality in a rural Chinese population

BACKGROUND

Tooth loss has been reported to be associated with the risk of liver cancer in several prior studies in economically advantaged countries. Whether this relationship is also evident in economically disadvantaged populations is not known.

METHODS

We analyzed data from the Nutrition Intervention Trials, two randomized placebo-controlled trials of vitamin/mineral supplementation in Linxian, China. Participants who reported having lost permanent teeth were examined to determine the number of teeth remaining. In the 30-year follow-up period, 329 liver cancers were diagnosed and 368 chronic liver disease deaths occurred. Tooth loss was categorized based on loess smoothed age-specific predicted quartiles. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the two outcomes.

RESULTS

Overall, persons in the highest quartile of age-specific tooth loss had an increased risk of liver cancer (HR = 1.27, 95%CI: 0.96, 1.67) which was not statistically significant. Results varied by sex and body mass index (BMI), however. Women in the highest quartile of age-specific tooth loss had a significantly increased risk (HR = 1.64, 95%CI: 1.04, 2.59), while men did not (HR = 1.08, 95%CI = 0.75, 1.57), and persons with a BMI > 23.0 kg/m2 (HR = 1.71, 95%CI: 1.00, 2.92) had a significantly increased risk, while persons with a BMI <23.0 kg/m2 did not (HR = 1.14, 95%CI: 0.82, 1.5). No relationships with chronic liver disease mortality were observed.

CONCLUSIONS

In a rural, economically disadvantaged population, persons with the highest levels of age-specific tooth loss had an increased risk of liver cancer. The results, which were stronger among women and persons with greater BMI, suggest that periodontal disease may increase risk of liver cancer.

A prospective study of cancer risk among Agricultural Health Study farm spouses associated with personal use of organochlorine insecticides

BACKGROUND

Organochlorine insecticides (OCs) have historically been used worldwide to control insects, although most have now been banned in developed countries. Evidence for an association between OC exposures and cancer predominantly comes from occupational and population based-studies among men. We evaluated the association between the use of specific OCs and cancer among the female spouses of pesticide applicators in the Agricultural Health Study.

METHODS

At enrollment (1993-1997), spouses of private applicators in the cohort provided information about their own use of pesticides, including seven OCs (aldrin, chlordane, dieldrin, DDT, heptachlor, lindane, and toxaphene), and information on potential confounders. We used Poisson regression to estimate relative risks (RRs) and 95% confidence intervals (CIs) for cancers (n ≥ 3 exposed cases) reported to state cancer registries from enrollment through 2012 (North Carolina) and 2013 (Iowa), and use of the individual OCs, as well as use of any of the specific OCs.

RESULTS

Among 28,909 female spouses, 2191 (7.58%) reported ever use of at least one OC, of whom 287 were diagnosed with cancer. Most cancers were not associated with OC use. Risk of glioma was increased among users of at least one OC (Nexposed = 11, RR = 3.52, 95% CI 1.72-7.21) and specifically among lindane users (Nexposed = 3, RR = 4.45, 95% CI 1.36-14.55). Multiple myeloma was associated with chlordane (Nexposed = 6, RR = 2.71, 95% CI 1.12-6.55). Based on 3 exposed cases each, there were also positive associations between pancreatic cancer and lindane, and ER-PR- breast cancer and dieldrin. No other associations with breast cancer were found.

CONCLUSIONS

Overall, there were some associations with OC use and cancer incidence, however we were limited by the small number of exposed cancer cases. Future research should attempt to expand on these findings by assessing environmental sources of OC exposures, to fully evaluate the role of OC exposures on cancer risk in women.

Pesticide exposure and liver cancer: a review

PURPOSE

To review the epidemiologic literature examining pesticide exposure and liver cancer incidence.

METHODS

A search of the MEDLINE and Embase databases was conducted in October 2015. Eligibility criteria included examining hepatocellular carcinoma (HCC) or primary liver cancer, pesticides as an exposure of interest, and individual-level incidence. The review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Forty-eight papers were assessed for eligibility and 15 studies were included in the review. The majority of studies were conducted in China and Egypt (n = 8), used a case-control design (n = 14), and examined HCC (n = 14). Most studies showed no association between self-reported and/or occupational exposure to pesticides and liver cancer risk. Six studies demonstrated statistically significant positive associations, including three biomarker-based studies (two using pre-diagnostic sera) that reported higher serum levels of dichlorodiphenyltrichloroethane (DDT) were associated with increased HCC risk. Studies indirectly measuring pesticide exposure using self-reported exposure, occupation, job-exposure matrices, or geographic residence demonstrated inconsistent results. These studies were limited by exposure assessment methods, lack of confounder information, minimal case confirmation, selection bias, and/or over-adjustment.

CONCLUSIONS

There is mixed evidence suggesting a possible association between specific pesticides and HCC risk, with the strongest evidence observed in biomarker-based studies. In particular, organochlorine pesticides, including DDT, may increase HCC risk. Future research should focus on improved pesticide exposure assessment methods, potentially incorporating multiple approaches including biomonitoring while considering the chemicals of interest, historical exposure to address latency periods, and examining specific chemicals and exposure pathways.

Non‑infective occupational risk factors for hepatocellular carcinoma: A review (Review)

Liver cancer is the second leading worldwide cause of cancer‑associated mortalities. Hepatocellular carcinoma, which accounts for the majority of liver tumors, ranks fifth among types of human cancer. Well‑established risk factors for liver cancer include the hepatitis B and C viruses, aflatoxins, alcohol consumption, and oral contraceptives. Tobacco smoking, androgenic steroids, and diabetes mellitus are suspected risk factors. Current knowledge regarding non‑infective occupational risk factors for liver cancer is inconclusive. The relevance of liver disorders to occupational medicine lies in the fact that the majority of chemicals are metabolized in the liver, and toxic metabolites generated via metabolism are the predominant cause of liver damage. However, their non‑specific clinical manifestations that are similar in a number of liver diseases make diagnosis difficult. Furthermore, concomitant conditions, such as viral hepatitis and alcohol or drug abuse, may mask liver disorders that result from occupational hepatotoxic agents and block the demonstration of an occupational cause. The identification of environmental agents that result in human cancer is a long and often difficult process. The purpose of the present review is to summarize current knowledge regarding the association of non‑infective occupational risk exposure and HCC, to encourage further research and draw attention to this global occupational public health problem.

Concentrations of organochlorine pesticides in umbilical cord blood and related lifestyle and dietary intake factors among pregnant women of the Huaihe River Basin in China

Organochlorine pesticides (OCPs), one of the persistent organic pollutants (POPs) with highly lipophilic properties, long half-lives, and persistence in the environment, are prevalent in the environment even though they have been banned for >30years. We aimed to investigate the current OCP exposure levels in cord blood from healthy pregnant women residing in the Huaihe River Basin, China, and examined the association between OCP levels and dietary habits and lifestyle factors. In this study, we measured the exposure levels of 17 OCPs in the umbilical cord blood from 999 healthy pregnant women; we also administered 1000 self-reported questionnaires regarding the general characteristics and dietary habits of those women. Our results showed that ρ,ρ'-DDE, ρ,ρ'-DDT, aldrin, dieldrin, and methoxychlor, which had higher measured concentrations (2.01±1.89, 4.31±5.68, 7.29±8.74, 5.27±7.65, and 0.98±1.42ng/mL, respectively) and detection frequencies (99.69%, 100.00%, 81.79%, 75.00%, and 74.49%, respectively), were the predominant OCPs in cord blood, and the higher levels of DDTs, aldrin, dieldrin, and methoxychlor were mainly due to recent use. In addition, most of the HCHs in cord blood were derived not only from historical use of technical HCH, but also from the additional use of lindane. In addition, we found that the education level of the pregnant women and monthly household income were positively correlated with OCP levels, particularly ρ,ρ'-DDE, aldrin, and dieldrin. Furthermore, the consumption of red meat (pork, beef, and lamb), fish, and bean products may be an important contributing factor to the increased concentrations of OCPs in cord blood, while the intake of poultry and pickles was negatively correlated with aldrin level. This study is the first to provide adequate data on current OCP exposure levels in cord blood from pregnant women in the Huaihe River Basin.

The effect of acute dichlorodiphenyltrichloroethane exposure on hypermethylation status and down-regulation of p53 and p16INK4a genes in rat liver

The aim of the study was to investigate the early effect of acute dichlorodiphenyltrichloroethane (DDT) exposure on the methylation status of the promoter region of two tumor suppressor genes: p53 and p16(INK4a) (p16) in rat liver. We analyzed their transcript and protein expression profiles concurrently with the examination of transcriptional and protein expression levels of DNA (cytosine-5)-methyltransferase 1 (Dnmt1). Male Wistar rats were treated with a single dose of DDT (57 mg kg(-1) of body weight) and the methylation status of p53 and p16 genes was examined after 24 h using methylation-sensitive restriction analysis-MSRA. The obtained results indicate that DDT induced alternations in methylation of the promoter region in both p53 and p16 genes. In all the tested samples, the promoter CpG islands of p53 (-261, -179, and -450) were methylated within 100% as compared to control samples (0%). The methylation status of the p16 promoter (-11 and +77) was also altered due to exposure to DDT. Methylated cytosines were detectable in 75% of the tested DNA samples. The Real-time PCR and western blot analyses showed a decrease in mRNA and protein levels of p53, respectively, which was related to the increase in DNA synthesis. These relationships were also observed for mRNA and protein expressions of p16, although to a slighter extent. We also showed that hypermethylation in the promoter region of both tumor suppressor genes was consistent with an increased Dnmt1 mRNA level, and this relationship was further confirmed at the protein level of DNMT1. Concluding, our data suggests that epigenetically mediated changes in gene expression may play an important role in the mechanism of DDT toxicity, including carcinogenic action.

Common cancer in a wild animal: the California sea lion (Zalophus californianus) as an emerging model for carcinogenesis

Naturally occurring cancers in non-laboratory species have great potential in helping to decipher the often complex causes of neoplasia. Wild animal models could add substantially to our understanding of carcinogenesis, particularly of genetic and environmental interactions, but they are currently underutilized. Studying neoplasia in wild animals is difficult and especially challenging in marine mammals owing to their inaccessibility, lack of exposure history, and ethical, logistical and legal limits on experimentation. Despite this, California sea lions (Zalophus californianus) offer an opportunity to investigate risk factors for neoplasia development that have implications for terrestrial mammals and humans who share much of their environment and diet. A relatively accessible California sea lion population on the west coast of the USA has a high prevalence of urogenital carcinoma and is regularly sampled during veterinary care in wildlife rehabilitation centres. Collaborative studies have revealed that genotype, persistent organic pollutants and a herpesvirus are all associated with this cancer. This paper reviews research to date on the epidemiology and pathogenesis of urogenital carcinoma in this species, and presents the California sea lion as an important and currently underexploited wild animal model of carcinogenesis.

Dichlorodiphenyldichloroethylene exposure reduces r-GCS via suppressed Nrf2 in HepG2 cells

p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE), the major isomer of persistent 1,1-Bis(4-chlorophenyl)-2,2,2-trichloroethane metabolite, is highly associated with the risk of liver cancer. γ-glutamyl-cysteine synthetase (γ-GCS), which is the rate-limiting enzyme of glutathione (GSH) biosynthesis and an important scavenger of reactive oxygen species (ROS), is considered as a potential therapeutic target for many cancers. However, the association between the body burden of p,p'-DDE and γ-GCS has not been fully established. Here, we indicated that low doses of p,p'-DDE exposure promoted the proliferation and decreased γ-GCS activity of HepG2 cells in a dose- and time-dependent manner. In addition, p,p'-DDE elevated ROS content and attenuated glutathione peroxidase activity. This was accompanied with inhibitions of NF-E2-related factor 2 (Nrf2) at the mRNA and protein levels. ROS inhibitor supplement could significantly reverse these effects. Moreover, the addition of the proteasome inhibitor, MG132, strongly reversed the p,p'-DDE-reduced Nrf2 expression and γ-GCS activity. Consistently, GSH content was in line with the alteration of γ-GCS. Collectively, the results indicate that p,p'-DDE treatment downregulates γ-GCS activity in HepG2 cells by inducing ROS-mediated Nrf2 loss.

Organochlorine pesticides in follicular fluid of women undergoing assisted reproductive technologies from central China

Female infertility rates have increased by approximately 4% since the 1980s. There is evidence of adverse effects on female fertility in relation to exposure of chemical pollution in recent years. Follicular fluid samples were collected from 127 woman patients (aged 20-35) who underwent assisted reproductive technologies (ART) and had no records indicating occupational exposure to OCPs. Seventeen OCPs were analyzed in this study. The results showed that methoxychlor was dominant, accounted for 13.4% of total OCPs with a mean concentration of 167.9 ± 33.9 ng/g lipid weight (lw), followed by heptachlor-epoxide, hexachlorocyclohexanes, endrin and DDT. The concentrations of OCPs in the follicular fluid samples in the present study were moderate in comparison with those reported from developed or industrialized countries. All these pollutants can accumulate in different tissues of human body through diet, drinking water and respiration. No correlation between patient age and OCP concentrations was observed in this study.

Pesticide exposure and hepatocellular carcinoma risk: A case-control study using a geographic information system (GIS) to link SEER-Medicare and California pesticide data

BACKGROUND

Hepatocellular carcinoma (HCC), the most common type of primary liver cancer, is associated with low survival. U.S. studies examining self-reported pesticide exposure in relation to HCC have demonstrated inconclusive results. We aimed to clarify the association between pesticide exposure and HCC by implementing a novel data linkage between Surveillance, Epidemiology, and End Results (SEER)-Medicare and California Pesticide Use Report (PUR) data using a geographic information system (GIS).

METHODS

Controls were frequency-matched to HCC cases diagnosed between 2000 and 2009 in California by year, age, race, sex, and duration of residence in California. Potential confounders were extracted from Medicare claims. From 1974 to 2008, pounds (1 pound represents 0.45 kg) of applied organophosphate, organochlorine, and carbamate pesticides provided in PURs were aggregated to the ZIP Code level using area weighting in a GIS. ZIP Code exposure estimates were linked to subjects using Medicare-provided ZIP Codes to calculate pesticide exposure. Agricultural residents were defined as living in ZIP Codes with a majority area intersecting agricultural land cover according to the 1992, 2001, and 2006 National Land Cover Database (NLCD) rasters. Multivariable conditional logistic regression was used to estimate the association between pesticide exposure and HCC.

RESULTS

Among California residents of agriculturally intensive areas, previous annual ZIP Code-level exposure to over 14.53 kg/km(2) of organochlorine pesticides (75(th) percentile among controls) was associated with an increased risk of HCC after adjusting for liver disease and diabetes (adjusted odds ratio [OR] 1.87, 95% confidence interval [CI] 1.17, 2.99; p=0.0085). ZIP Code-level organochlorines were significantly associated with an increased risk of HCC among males (adjusted OR 2.76, 95% CI 1.58, 4.82; p=0.0004), but not associated with HCC among females (adjusted OR 0.83, 95% CI 0.35, 1.93; p=0.6600) (interaction p=0.0075).

CONCLUSIONS

This is the first epidemiologic study to use GIS-based exposure estimates to study pesticide exposure and HCC. Our results suggest that organochlorine pesticides are associated with an increase in HCC risk among males but not females.

Hematological and hepatic alterations in Brazilian population heavily exposed to organochlorine pesticides

The aim of this study was to investigate the frequency of hematological and hepatic alterations and possible association with serum levels of beta-hexachlorocyclohexane (beta-HCH), p,p'-DDE, and hexachlorobenzene (HCB) among residents in an area heavily contaminated with organochlorine (OC) pesticides. A cross-sectional study was conducted in 415 male and 432 female residents aged >14 years. Serum samples were collected and analyzed for OC pesticides concentrations and biochemical parameters. Frequencies of hematological and hepatic alterations were calculated for each gender. Association between beta-HCH, p,p'-DDE (1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene), and HCB levels and presence of alterations was determined by logistic regression stratified by gender and controlling for confounders. Highest frequencies were observed for eosinophilia (23% men and 18% women), low hemoglobin (12% men and 15% women), and low erythrocyte count (12% men). High levels of bilirubin, glutamic-oxaloacetic transaminase (GOT), and glutamic-pyruvic transaminase (GPT) were observed, respectively, in 10, 11, and 12% of men and <10% of women. Gamma-glutamyl transferase (GGT) was elevated in 26 and 25% of males and females, respectively. Multivariate analysis revealed associations between eosinophilia and beta-HCH in men (OR = 1.06, 95%CI = 1.01-1.12) and women (OR = 1.05, 96%CI = 0.99-1.11), p,p'-DDE in men (OR = 1.03, 95%CI = 0.99-1.06) and women (OR = 1.02, 95%CI = 0.99-1.06), and HCB in women (OR = 1.54, 95%IC = 0.85-4.45). Beta-HCH was found to be associated with increased risk of elevated bilirubin in females (OR = 1.18, 95%CI = 1.07-1.29) and males (OR = 4.21, 95%CI = 1.87-9.47 for fourth vs. first quintile). Thus, OC pesticides may exert adverse effects on hematopoietic tissue and liver in populations chronically exposed to high levels of these compounds.

p,p′-Dichlorodiphenyltrichloroethane inhibits the apoptosis of colorectal adenocarcinoma DLD1 cells through PI3K/AKT and Hedgehog/Gli1 signaling pathways

p,p′-Dichlorodiphenyltrichloroethane is able to inhibit the apoptosis of human colorectal adenocarcinoma cells, which may be an important mechanism to contribute to colorectal cancer development.

The organochlorine p,p'-dichlorodiphenyltrichloroethane induces colorectal cancer growth through Wnt/β-catenin signaling

Dichlorodiphenyltrichloroethane (DDT), an organochlorine pollutant, is associated with several types of cancer. However, the relationship between DDT and colorectal cancer is uncertain. In this study, the impact of p,p'-DDT on colorectal cancer growth was evaluated using both in vitro and in vivo models. Our results indicated that the proliferation of human colorectal adenocarcinoma DLD1 cells was significantly promoted after exposed to low concentrations of p,p'-DDT ranging from 10(-12) to 10(-7) M for 96 h. Exposure to p,p'-DDT from 10(-10) to 10(-8) M led to upregulation of phospho-GSK3β (Ser9), β-catenin, c-Myc and cyclin D1 in DLD1 cells. RNA interference of β-catenin inhibited the proliferation of DLD1 cells stimulated by p,p'-DDT. Inhibiting of estrogen receptors (ERs) had no significant effect on the action of p,p'-DDT. Treatment with p,p'-DDT induced production of intracellular reactive oxygen species (ROS) and inhibited superoxide dismutase (SOD) activity in DLD1 cells. Treatment with N-acetyl-L-cysteine (NAC), a ROS inhibitor, suppressed the induction of Wnt/β-catenin signaling and DLD1 cell proliferation by p,p'-DDT. Moreover, in a mouse xenograft model, 5 nmol/kg p,p'-DDT resulted in increased tumor size, oxidative stress and Wnt/β-catenin signaling. These results indicated that low concentrations of p,p'-DDT promoted colorectal cancer growth through Wnt/β-catenin signaling, which was mediated by oxidative stress. The finding suggests an association between low concentrations of p,p'-DDT exposure and colorectal cancer progression.

The evaluation of p,p'-DDT exposure on cell adhesion of hepatocellular carcinoma

Many studies have found a positive association between the progression of hepatocellular carcinoma and DDT exposure. These studies mainly focus on the effect of DDT exposure on cell proliferation and epithelial to mesenchymal transition (EMT) promotion. However, the influence of DDT on cell adhesion of hepatocellular carcinoma remains to be unclear. The aim of our study was to determine the effect of p,p'-DDT on cell adhesion of hepatocellular carcinoma in vitro and in vivo. The data showed that p,p'-DDT, exposing HepG2 cells for 6 days, decreased cell-cell adhesion and elevated cell-matrix adhesion. Strikingly, p,p'-DDT increased reactive oxygen species (ROS) content, and this was accompanied by the activation of JAK/STAT3 pathway. Moreover, ROS inhibitor supplement reversed these effects significantly. However, the addition of ER inhibitor, ICI, had no effect on the p,p'-DDT-induced effects. p,p'-DDT altered the mRNA levels of related adhesion molecules, including inhibition of E-cadherin and promotion of N-cadherin along with CD29. Interestingly, the p,p'-DDT-altered adhesion molecules could be reversed with JAK inhibitor or STAT3 inhibitor. Likewise, p,p'-DDT stimulated the JAK/STAT3 pathway in nude mice, as well as altered the mRNA levels of E-cadherin, N-cadherin, and CD29. Taken together, these results indicate that p,p'-DDT profoundly promotes the adhesion process by decreasing cell-cell adhesion and inducing cell-matrix adhesion via the ROS-mediated JAK/STAT3 pathway. All these events account for the carcinogenic potential of p,p'-DDT in liver.

Dichlorodiphenyltrichloroethane exposure induces the growth of hepatocellular carcinoma via Wnt/β-catenin pathway

Dichlorodiphenyltrichloroethane (DDT) is a persistent organic pollutant, involved in the progression of many cancers, including liver cancer. However, the underlying mechanism(s) of DDT, especially how low doses DDT cause liver cancer, is poorly understood. In this study, we evaluated the impact of p,p'-DDT on the growth of hepatocellular carcinoma using both in vitro and in vivo models. The present data indicated that the proliferation of HepG2 cells was strikingly promoted after exposed to p,p'-DDT for 4 days. In addition, reactive oxygen species (ROS) content was significantly elevated, accompanied with inhibitions of γ-glutamylcysteine synthetase (γ-GCS) and superoxide dismutase (SOD) activities. Interestingly, the levels of β-catenin and its downstream target genes (c-Myc and CyclinD1) were significantly up-regulated, and co-treatment of NAC, the ROS inhibitor, inhibited these over-expressed proteins. Moreover, the p,p'-DDT-stimulated proliferation of HepG2 cells could be reversed after NAC or β-catenin siRNA co-treatment. Likewise, p,p'-DDT treatment increased the growth of tumor in nude mice, stimulated oxidative stress and Wnt/β-catenin pathway. Our study indicates that low doses p,p'-DDT exposure promote the growth of hepatocellular carcinoma via Wnt/β-catenin pathway which is activated by oxidative stress. The finding suggests an association between low dose DDT exposure and liver cancer growth.

Contamination of polychlorinated biphenyls and organochlorine pesticides in breast milk in Korea: time-course variation, influencing factors, and exposure assessment

Breast milk is a noninvasive specimen to assess maternal and infant exposure to polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). In this study, 206 breast milk samples were collected from 87 participants during lactation, at <7, 15, 30, or 90 days postpartum in four cities in Korea. The total concentrations of PCBs (ΣPCB) and OCPs (ΣOCP) ranged from <LOQ to 84.0 (median: 12.1) ng g(-1) lipid weight and from <LOQ to 559 (median: 144) ng g(-1) lipid weight, respectively. The residue levels of these contaminants measured in our study were relatively lower than those reported for European, African and Asian populations. Within a month postpartum typically after day seven the levels of ΣPCB and ΣOCP significantly increased. Some OCP compounds were correlated with maternal age, BMI, parity, and delivery mode. Certain types of dietary habits such as seafood and noodle consumption were significantly associated with ΣPCB and ΣOCP. The estimated daily intakes (EDIs) of ΣPCB and ΣOCP were 45.2-127 ng kg(-1) bw day(-1) and 625-1259 ng kg(-1) bw day(-1) during lactation, respectively, which are lower than the threshold values proposed by the US EPA and Health Canada. The exposure of Korean infants to chlordanes via breast milk had a potential health risk which deserves further investigation.

Placental transfer of persistent organic pollutants: a preliminary study on mother-newborn pairs

The aim of this study was to characterize the placental transfer of some environmental pollutants, and to explore the possibility of quantitatively predicting in utero exposure to these contaminants from concentrations assessed in maternal blood. Levels of toxic substances such as pesticides (p,p'-DDE, β-HCH, and HCB), polychlorinated biphenyls (PCBs), perfluorooctane sulfonate (PFOS), and perfluorooctanoic acid (PFOA) were determined in serum samples of 38 pregnant women living in Rome and in samples of cord blood from their respective newborns. The study was carried out in the years 2008-2009. PCB mean concentrations in maternal serum and cord serum ranged from 0.058 to 0.30, and from 0.018 to 0.064 ng/g · fw respectively. Arithmetic means of PFOS and PFOA concentrations in mothers and newborns were 3.2 and 1.4 ng/g · fw, and 2.9 and 1.6 ng/g · fw. A strong correlation was observed between concentrations in the maternal and the foetal compartment for PFOS (Spearman r = 0.74, p < 0.001), PFOA (Spearman r = 0.70, p < 0.001), PCB 153 (Spearman r = 0.60, p < 0.001), HCB (Spearman r = 0.68, p < 0.001), PCB 180 (Spearman r = 0.55, p = 0.0012), and p,p'-DDE (Spearman r = 0.53, p = 0.0099). A weak correlation (p < 0.1) was observed for PCBs 118 and 138.

Association of XRCC1, XRCC3, and XPD genetic polymorphism with an increased risk of hepatocellular carcinoma because of the hepatitis B and C virus

OBJECTIVE

The south-east Asian and sub-Saharan African populations are the most susceptible to hepatocellular carcinoma (HCC). We aimed to establish whether XRCC1, XRCC3, and XPD are associated with liver cancer in Pakistan and to examine the interaction of hepatitis B virus (HBV) or hepatitis C virus (HCV) with repaired genes in the occurrence of liver cancer.

MATERIALS AND METHODS

We enrolled 74 healthy individuals, 75 had either HBV or HCV, and 50 were HCC patients. The characteristic information of all the study participants were collected through a standard interviewer-administered questionnaire. The PCR-RFLP was used to identify the genotype of the patients.

RESULTS

The results of our study indicated that the patients infected with HBV or HCV had a four or three-fold greater risk of developing liver cancer. Patients older than 55 years of age had a significantly higher risk of developing cancer compared with younger patients. The homozygous wild types Arg/Arg for 280 and Thr/Thr for 241 were more frequent in the controls than in the cases. The allelic frequency of mutant 280His and 399Gln was more pronounced among HCC cases than the controls or the HBV-infected patients.

CONCLUSION

The frequency of the XPD gene in the controls was in Hardy-Weinberg equilibrium, indicating that the gene played a protective role in the Pakistani population. XRCC1 or XRCC3 was associated with liver cancer in the Pakistani population; however, the XPD gene played a vital role in the repair of DNA damage.

Sustainable malaria control: transdisciplinary approaches for translational applications

With the adoption of the Global Malaria Action Plan, several countries are moving from malaria control towards elimination and eradication. However, the sustainability of some of the approaches taken may be questionable. Here, an overview of malaria control and elimination strategies is provided and the sustainability of each in context of vector- and parasite control is assessed. From this, it can be concluded that transdisciplinary approaches are essential for sustained malaria control and elimination in malaria-endemic communities.

Exposure to organochlorine pesticides is an independent risk factor of hepatocellular carcinoma: a case-control study

Primary hepatocellular carcinoma (HCC) is highly prevalent in China. Although hepatitis B virus (HBV) and aflatoxin B1 (AFB1) are considered the major risk factors, among the high-risk cohorts only a small fraction develops liver cancer. Therefore, we investigated whether organochlorine pesticide exposure contributed to HCC risk in the Xiamen population. The questionnaire database was built from 346 HCC cases and 961 healthy controls during 2007-2009. The serum levels of α-, β-, γ-, δ-HCH, 1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane (p,p'-DDT), (1,1-dichloro-2,2-bis (p-chlorophenyl) ethylene (p,p'-DDE), 1,1,1-trichloro-2,2-bis (o-chlorophenyl) ethane and 1,1-dichloro-2,2-bis (p-chlorophenyl) ethane were measured by gas chromatography-tandem mass spectrometer, and statistical analysis was done using SPSS16. Significantly, we observed p,p'-DDT and p,p'-DDE, and at the first time β-HCH displayed quartile dose-dependent HCC risk trends; p,p'-DDT showed positive (i.e., synergistic) interactions with HBV, diabetes mellitus, AFB1 and polyaromatic hydrocarbon (PAH) exposure, but negative (i.e., antagonistic) interaction with heavy drinking; p,p'-DDE had positive interaction with PAH but negative interaction with HBV and p,p'-DDT; and β-HCH positively interacted with p,p'-DDT but negatively interacted with heavy drinking and diabetes. p,p'-DDT, p,p'-DDE and β-HCH were independent HCC risk factors. Because of their synergistic interactions with other factors, the high-level exposure combined with common AFB1 and HBV exposure in the investigated area may greatly enhance the risk of HCC.

Risk of hepatocellular carcinoma in workers exposed to chemicals

CONTEXT

Studies on experimental animals have shown liver is a common target of chemical carcinogens; this might suggest that occupational exposure to chemicals is another risk factor for HCC. However, the relationship between occupation and liver cancer has not been extensively studied, with the exception of the known association between vinyl chloride and angiosarcoma of the liver.

EVIDENCE ACQUISITION

A MEDLINE and conventional search of the past 50 years of the medical literature was performed to identify relevant articles on incidence and mechanisms of HCC due to occupational exposure to chemicals. Several important edited books and monographs were also identified and reviewed.

RESULTS

While laboratory data clearly indicate that the liver is an important target of chemical carcinogenesis, epidemiological studies provide very limited evidence on occupational risk factors for HCC. Nevertheless, we found some case reports and epidemiological data showing a moderately increased risk of HCC development in people exposed to vinyl chloride, organic solvents, pesticides, polychlorinated biphenyls, and arsenic.

CONCLUSIONS

Occupational exposure to chemicals may be another risk factor for HCC development, but the interpretation of currently available findings is limited by the small number of studies, questionable accuracy of the diagnosis of liver cancer, and potential confounding or modifying factors such as chronic hepatitis virus infection and alcohol consumption. Further relevant investigations are required for clarifying the actual contribution of occupational exposure to chemicals in HCC development.

Dichlorodiphenyltrichloroethane and risk of hepatocellular carcinoma

Dichlorodiphenyltrichloroethane (p,p'-DDT), an organochlorine pesticide known to have deleterious health effects in humans, has been linked to hepatocellular carcinoma (HCC) in rodents. A recent study has reported that p,p'-DDT and its most persistent metabolite, dichlorodiphenyldichloroethylene (p,p'-DDE), may also be associated with HCC in humans. To examine whether there is an association between p,p'-DDT and/or p,p'-DDE in a population at high-risk of developing HCC, a nested case-control study was conducted within the 83,794 person Haimen City Cohort in China. Sera and questionnaire data were collected from all participants between 1992 and 1993. This study included 473 persons who developed HCC and 492 who did not, frequency matched on sex, age and area of residence. p,p'-DDT and p,p'-DDE levels were determined by mass spectrometry. Hepatitis B viral infection status (based on hepatitis B virus surface antigen; HBsAg) was also determined. p,p'-DDT and/or p,p'-DDE serum levels were significantly associated with sex, area of residence, occupation, alcohol consumption and cigarette smoking. Adjusting for age, sex, area of residence, HBsAg, family history of HCC, history of acute hepatitis, smoking, alcohol, occupation (farmer vs. other) and levels of p,p'-DDT or p,p'-DDE, odds ratios (OR) and 95% confidence intervals (CI) were calculated via unconditional logistic regression. Overall, the highest quintile of p,p'-DDT was associated with an increased risk of HCC, OR = 2.96 95% CI; 1.19-7.40. There were no statistically significant associations with p,p'-DDE. Overall, these results suggest that recent exposure to p,p'-DDT may increase risk of HCC.

DDT and Other Chlorinated Insecticides

The use of organochlorine insecticides such as DDT, lindane and cyclodieneshas declined markedly worldwide over the last decades. Most are now banned or not used. At an acute toxicity level they have been relatively safe in use for humans. However, the greatest concerns are their persistence in people, wildlife and the environment due to their slow metabolism. Although their carcinogenicity for humans has not been supported by strong epidemiological evidence, their potential to be modulators of endocrine and immune function at levels remaining in the environment or associated with residual spraying of DDT continue to be of concern. At present, DDT is still allowed by the United Nations for combating malaria, with continual monitoring and assessment where possible. The toxicological consequences of exposure of animals and people to DDT is discussed as well as some analogues and other insecticides such as lindane, dieldrin and chlordecone that, although little used, continue to persist in surroundings and people. Because of circumstances of world health brought about by climate change or human activities that have yet to develop, there may come a time when the importance of some may re-emerge.

Application of computational systems biology to explore environmental toxicity hazards

BACKGROUND

Computer-based modeling is part of a new approach to predictive toxicology.

OBJECTIVES

We investigated the usefulness of an integrated computational systems biology approach in a case study involving the isomers and metabolites of the pesticide dichlorodiphenyltrichloroethane (DDT) to ascertain their possible links to relevant adverse effects.

METHODS

We extracted chemical-protein association networks for each DDT isomer and its metabolites using ChemProt, a disease chemical biology database that includes both binding and gene expression data, and we explored protein-protein interactions using a human interactome network. To identify associated dysfunctions and diseases, we integrated protein-disease annotations into the protein complexes using the Online Mendelian Inheritance in Man database and the Comparative Toxicogenomics Database.

RESULTS

We found 175 human proteins linked to p,p'-DDT, and 187 to o,p'-DDT.Dichlorodiphenyldichloroethylene (p,p'-DDE) was the metabolite with the highest number of links, with 52. We grouped proteins for each compound based on their disease annotations. Although the two data sources differed in linkage to diseases, integrated results predicted that most diseases were linked to the two DDT isomers. Asthma was uniquely linked with p,p'-DDT, and autism with o,p'-DDT. Several reproductive and neurobehavioral outcomes and cancer types were linked to all three compounds.

CONCLUSIONS

Computer-based modeling relies on available information. Although differences in linkages to proteins may be due to incomplete data, our results appear meaningful and suggest that the parent DDT compounds may be responsible for more disease connections than the metabolites. The findings illustrate the potential use of computational approaches to toxicology.

Fumonisin B1 and risk of hepatocellular carcinoma in two Chinese cohorts

Fumonisin B1 (FB1), a mycotoxin that contaminates corn in certain climates, has been demonstrated to cause hepatocellular cancer (HCC) in animal models. Whether a relationship between FB1 and HCC exists in humans is not known. To examine the hypothesis, we conducted case-control studies nested within two large cohorts in China; the Haimen City Cohort and the General Population Study of the Nutritional Intervention Trials cohort in Linxian. In the Haimen City Cohort, nail FB1 levels were determined in 271 HCC cases and 280 controls. In the General Population Nutritional Intervention Trial, nail FB1 levels were determined in 72 HCC cases and 147 controls. In each population, odds ratios and 95% confidence intervals (95%CI) from logistic regression models estimated the association between measurable FB1 and HCC, adjusting for hepatitis B virus infection and other factors. A meta-analysis that included both populations was also conducted. The analysis revealed no statistically significant association between FB1 and HCC in either Haimen City (OR=1.10, 95%CI=0.64-1.89) or in Linxian (OR=1.47, 95%CI=0.70-3.07). Similarly, the pooled meta-analysis showed no statistically significant association between FB1 exposure and HCC (OR=1.22, 95%CI=0.79-1.89). These findings, although somewhat preliminary, do not support an associated between FB1 and HCC.

Exposure to organochlorine pesticides is independent risk factor of hepatocellular carcinoma: a case--control study

Primary hepatocellular carcinoma (HCC) is highly prevalent in China. Although hepatitis B virus (HBV) and aflatoxin B1 (AFB1) are considered the major risk factors, among the high-risk cohorts only a small fraction develops liver cancer. Therefore, we investigated if organochlorine pesticides (OCPs) exposure contributed to HCC risk in the Xiamen population. The questionnaire database was built from 346 HCC cases and 961 healthy controls during 2007-2009. The serum levels of α-, β-, γ-, δ-HCH, p, p'-DDT, p, p'-DDE, o, p'-DDT and p, p'-DDD were measured by gas chromatography-tandem mass spectrometer and statistical analysis was done using SPSS16. Significantly, we observed p, p'-DDT, p, p'-DDE, and at first time β-HCH displayed quartile dose-dependent HCC risk trends; p, p'-DDT showed positive (i.e., synergistic) interactions with HBV, diabetes mellitus, AFB1 and polycyclic aromatic hydrocarbon (PAH) exposure, but negative (i.e., antagonistic) interaction with heavy drinking; p, p'-DDE had positive interaction with PAH but negative interaction with HBV and p, p'-DDT; and β-HCH was positively interacted with p, p'-DDT but negatively interacted with heavy drinking and diabetes. p, p'-DDT, p, p'-DDE and β-HCH were independent HCC risk factors. Because of their synergistic interactions with other factors, the high level exposure combined with common AFB1 and HBV exposure in the investigated area may greatly enhance the risk of HCC.

Relationship between serum concentrations of polychlorinated biphenyls and organochlorine pesticides and dietary habits of pregnant women in Shanghai

The use of most polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) has been restricted in China; however, their use remains a concern because of their adverse effects on human health, especially on fetuses and infants. To date, there is no data regarding the exposure levels of pregnant women to PCBs and OCPs in Shanghai. In order to evaluate PCB and OCP exposure levels and the contribution of dietary habits to these levels, we determined the concentrations of 8 PCBs and 14 OCPs in the umbilical cord blood serum of healthy pregnant women in Shanghai. Dietary habits of the pregnant women were obtained from a self-administered questionnaire. Results showed that p, p'-DDE, HCB and β-HCH were the major pollutants present in the serum samples; PCBs were detected in a few samples at low concentrations. Age, weight and body mass index before delivery were positively associated with serum levels of p, p'-DDE and β-HCH. Women and their husbands who had higher education levels, higher income levels, tended to have higher levels of p, p'-DDE and β-HCH. Spearman correlation analysis results suggested that consumption of foods such as milk, eggs, meat, fish, and shrimp may contribute to higher serum levels of p, p'-DDE and β-HCH. Furthermore, multiple linear regression analyses indicated that the age and educational levels of the pregnant women and their intake of fried/flamed food and shellfish were positively associated with β-HCH levels, and that the age and educational levels of the pregnant women and their intake of parity, beef, pork, mutton, and shrimp were positively associated with p, p'-DDE levels. This is the first study to investigate the exposure levels of pregnant women to PCBs and OCPs in Shanghai, and it should provide useful information for future related research.

Distribution of blood concentrations of persistent organic pollutants in a representative sample of the population of Catalonia

BACKGROUND

Although virtually all populations worldwide are commonly exposed to numerous persistent organic pollutants (POPs) and human concentrations vary widely, only a few countries conduct nationwide surveillance programs of POP concentrations in representative samples of the general population.

OBJECTIVE

To evaluate the distribution of serum concentrations of nineteen POPs and their main predictors in a representative sample of the general population of Catalonia.

METHODS

Participants in the Catalan Health Interview Survey aged 18-74 years were interviewed face-to-face, gave blood, and underwent a physical exam. Graphs (including "POP Geoffrey Rose curves") were used to represent the full population distribution of each POP in the 919 participants. Through multivariate statistical models we analyzed the influence on POP concentrations of sex, age, body mass index (BMI), socioeconomic status and, in women, parity.

RESULTS

We detected dichlorodiphenyltrichloroethane (p,p'-DDT), dichlorodiphenyldichloroethane (p,p'-DDE), polychlorinated biphenyls (PCBs) congeners 118, 138, 153 and 180, hexachlorobenzene (HCB) and beta-hexachlorocyclohexane (beta-HCH) in more than 85% of the subjects. p,p'-DDE, HCB and beta-HCH showed the highest concentrations (median=399, 159 and 92 ng/g lipid, respectively). Distributions were highly skewed and interindividual differences were up to 7700-fold. POP levels differed significantly by gender, age, BMI, educational level, and parity.

CONCLUSIONS

In Catalonia, an advanced European society, exposure to POPs remains common, a vast majority of the population has much lower blood concentrations than a relative minority, and the population distributions of POP are hence highly skewed to the right. Shifting distributions towards lower concentrations requires more energetic policies and population strategies.

Prenatal DDT exposure and testicular cancer: a nested case-control study

The authors examined maternal serum levels of DDT-related compounds in relation to son's risk of testicular cancer 30 years later. Fifteen of 9,744 live-born sons were diagnosed with germ cell testicular cancer and had maternal serum samples. Cases were matched to three controls on race and birth year. Maternal serum DDT-related compounds, measured in the early postpartum, were associated with her son's risk of testicular cancer. Despite low statistical power, we observed that mothers of cases had a significantly higher ratio of p,p'-DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) to p,p'-DDE (1,1'-dichloro-2,2'-bis(p-chlorophenyl)ethylene) and lower o,p'-DDT (1,1,1-tricholoro-2-(p-chlororphenyl)-2-(o-chlorophenyl)ethane). These findings are consistent with earlier exposure to DDT and with slower p,p'-DDT elimination among mothers of cases. Whether these associations could be direct, or operate via other pathways is unknown. Further research on interindividual differences in DDT metabolism could provide clues to testicular cancer etiology.

DDT contamination from indoor residual spraying for malaria control

The insecticide DDT is still used in specific areas of South Africa for indoor residual spray (IRS) to control malaria vectors. Local residents could be exposed to residues of DDT through various pathways including indoor air, dust, soil, food and water. The aims of this study were to determine the levels of DDT contamination, as a result of IRS, in representative homesteads, and to evaluate the possible routes of human exposure. Two villages, exposed (DV) and reference (TV) were selected. Sampling was done two months after the IRS process was completed. Twelve homesteads were selected in DV and nine in TV. Human serum, indoor air, floor dust, outside soil, potable water, leafy vegetables, and chicken samples (muscle, fat and liver) were collected and analyzed for both the o,p'- and p,p'-isomers of DDT, DDD and DDE. DDT was detected in all the media analyzed indicating a combination of potential dietary and non-dietary pathways of uptake. DV had the most samples with detectable levels of DDT and its metabolites, and with the exception of chicken muscle samples, DV also had higher mean levels for all the components analyzed compared to TV. Seventy-nine percent of participants from DV had serum levels of DDT (mean [summation operator]DDT 7.3microg g(-1) lipid). These residues constituted mainly of p,p'-DDD and p,p'-DDE. [summation operator]DDT levels were detected in all indoor air (mean [summation operator]DDT 3900.0 ng m(-3)) and floor dust (mean [summation operator]DDT 1200.0 microg m(-2)) samples. Levels were also detected in outside soil (mean [summation operator]DDT 25.0 microg kg(-1)) and potable water (mean [summation operator]DDT 2.0 microg L(-1)). Vegetable sample composition (mean [summation operator]DDT 43.0 microg kg(-1)) constituted mainly p,p'-DDT and p,p'-DDD. Chicken samples were highly contaminated with DDT (muscle mean [summation operator]DDT 700.0 microg kg(-1), fat mean [summation operator]DDT 240,000.0 microg kg(-1), liver mean [summation operator]DDT 1600.0 microg kg(-1)). The results of the current study raise concerns regarding the potential health effects in residents living in the immediate environment following DDT IRS.

The relative influence of diet and serum concentrations of organochlorine compounds on K-ras mutations in exocrine pancreatic cancer

BACKGROUND

In exocrine pancreatic cancer (EPC) mechanistic relationships may exist among some organochlorine compounds (OCs) and mutations in the K-ras oncogene, as well as among the latter and dietary factors.

OBJECTIVE

To analyze (1) the relationship between food intake and serum concentrations of OCs in EPC patients and (2) the relative influence of food and OCs on the frequency of K-ras mutations in EPC.

PATIENTS AND METHODS

Incident cases of EPC were prospectively identified, and interviewed face-to-face during hospital admission (N=135 patients with data on OCs and diet, and N=97 with additional information on K-ras status). OCs were measured by high-resolution gas chromatography with electron-capture detection.

RESULTS

Consumption of milk and other dairy products was positively associated with concentrations of p,p'-DDT, PCB 138 and PCB 153 (log-transformed betas=0.652, 0.588 and 0.317, respectively; all p<0.05). When adjusted by OCs, dairy products were no longer associated with K-ras. By contrast, after adjusting by consumption of dairy products, patients with the highest concentrations of p,p'-DDT and some PCBs remained more likely to have a K-ras-mutated EPC than patients with lower concentrations (OR for upper tertile of PCB 138=5.5, 95% CI: 1.3-23.4).

CONCLUSIONS

Dairy products were a source of OCs. The association between dairy products and K-ras mutations was not independent of OCs. By contrast, the association between OCs and K-ras was not confounded by dairy products. OCs may be more likely to contribute to the occurrence of K-ras mutations than nutrients contained in dairy products.

Spatial analysis of hepatocellular carcinoma and socioeconomic status in China from a population-based cancer registry

BACKGROUND

Little is known about geographic variations in liver cancer at high incident regions. We aimed to identify spatial variation of hepatocellular carcinoma (HCC) at a high-risk area in China and determine its association with socioeconomic status (SES).

METHODS

Based on 2299 liver cancer cases diagnosed in Haimen from 2003 to 2006, we calculated age-sex standardized incidence ratios (SIRs) and used two spatial scan statistics to determine the geographic variations in HCC. Bayesian hierarchical model was used to explore the association between HCC incidence and SES.

RESULTS

Age and sex SIRs for HCC varied from 0.54 to 1.97 for 24 townships. The eastern region of Haimen was identified to have a significantly increased risk of HCC. Fitting of a Bayesian hierarchical model linking per-capita fiscal revenue with SIRs of HCC indicated that the area with a lower revenue had a significantly higher incidence of HCC [beta(log(revenue))=-0.179, posterior 95% Bayesian credible interval (CI)=(-0.326, -0.04)].

CONCLUSIONS

This study demonstrated substantial geographic variation in the incidence of HCC within a high-risk region, which was associated with SES. HCC control and intervention should focus on disadvantaged areas to reduce the HCC disparities.

In pancreatic ductal adenocarcinoma blood concentrations of some organochlorine compounds and coffee intake are independently associated with KRAS mutations

While KRAS activation is a fundamental initiating event in the aetiopathogenesis of pancreatic ductal adenocarcinoma (PDA), environmental factors influencing the occurrence and persistence of KRAS mutations remain largely unknown. The objective was to test the hypothesis that in PDA there are aetiopathogenic relationships among concentrations of some organochlorine compounds (OCs) and the mutational status of the KRAS oncogene, as well as among the latter and coffee intake. Incident cases of PDA were interviewed and had blood drawn at hospital admission (N = 103). OCs were measured by high-resolution gas chromatography with electron capture detection. Cases whose tumours harboured a KRAS mutation had higher concentrations of p,p'-dichlorodiphenyltrichloroethane (DDT), p,p'-dichlorodiphenyldichloroethene (DDE) and polychlorinated biphenyls (PCBs) 138, 153 and 180 than cases with wild-type KRAS, but differences were statistically significant only for p,p'-DDT and PCBs 138 and 153. The association between coffee intake and KRAS mutations remained significant (P-trend < 0.015) when most OCs where accounted for. When p,p'-DDT, PCB 153, coffee and alcohol intake were included in the same model, all were associated with KRAS (P = 0.042, 0.007, 0.016 and 0.025, respectively). p,p'-DDT, p,p'-DDE and PCB 138 were significantly associated with the two most prevalent KRAS mutations (Val and Asp). OCs and coffee may have independent roles in the aetiopathogenesis of PDA through modulation of KRAS activation, acquisition or persistence, plausibly through non-genotoxic or epigenetic mechanisms. Given that KRAS mutations are the most frequent abnormality of oncogenes in human cancers, and the lifelong accumulation of OCs in humans, refutation or replication of the findings is required before any implications are assessed.

The Pine River statement: human health consequences of DDT use

OBJECTIVES

Dichlorodiphenyltrichloroethane (DDT) was used worldwide until the 1970s, when concerns about its toxic effects, its environmental persistence, and its concentration in the food supply led to use restrictions and prohibitions. In 2001, more than 100 countries signed the Stockholm Convention on Persistent Organic Pollutants (POPs), committing to eliminate the use of 12 POPs of greatest concern. However, DDT use was allowed for disease vector control. In 2006, the World Health Organization and the U.S. Agency for International Development endorsed indoor DDT spraying to control malaria. To better inform current policy, we reviewed epidemiologic studies published from 2003 to 2008 that investigated the human health consequences of DDT and/or DDE (dichlorodiphenyldichloroethylene) exposure.

DATA SOURCES AND EXTRACTION

We conducted a PubMed search in October 2008 and retrieved 494 studies.

DATA SYNTHESIS

Use restrictions have been successful in lowering human exposure to DDT, but blood concentrations of DDT and DDE are high in countries where DDT is currently being used or was more recently restricted. The recent literature shows a growing body of evidence that exposure to DDT and its breakdown product DDE may be associated with adverse health outcomes such as breast cancer, diabetes, decreased semen quality, spontaneous abortion, and impaired neurodevelopment in children.

CONCLUSIONS

Although we provide evidence to suggest that DDT and DDE may pose a risk to human health, we also highlight the lack of knowledge about human exposure and health effects in communities where DDT is currently being sprayed for malaria control. We recommend research to address this gap and to develop safe and effective alternatives to DDT.