Cottonmouth snake bites reported to the ToxIC North American snakebite registry 2013-2017

Introduction: The majority of venomous snake exposures in the United States are due to snakes from the subfamily Crotalinae (pit vipers). There are three types of US pit vipers: rattlesnakes (Crotalus and Sisturus spp.) copperheads (Agkistrodon contortrix), and cottonmouths (Agkistrodon piscivorus) also known as water moccasins. Cottonmouth bites are reported less frequently than other pit viper envenomations, and data on cottonmouth envenomation are limited. Our objective was to describe the epidemiology, clinical manifestations, and management of cottonmouth envenomations using prospective data reported to the Toxicology Investigators Consortium's (ToxIC) North American Snakebite Registry (NASBR)Methods: Cottonmouth envenomation cases reported to NASBR for the period from January 1, 2013, through December 31, 2017 were reviewed. Variables collected included patient demographics, bite location, clinical manifestations, and management.Results: Thirty-one cottonmouth envenomations were reported. Most bites occurred in children aged 7-12 (39%). Most bites involved the lower extremity (72%). Intentional interaction with the snake occurred in three cases (10%). Swelling was the most reported clinical effect and occurred in all patients. Gastrointestinal symptoms were reported in 19% of patients, and 19% developed coagulopathy. Antivenom treatment was used in 84% of patients. Nineteen patients (61%) required hospital stays of >24 hours.Discussion: Our study represents the first systematic prospective data collection on cottonmouth bites. Our data demonstrate that cottonmouth envenomations cause primarily local effects and, occasionally, systemic toxicity. Our study also demonstrates that antivenom is often indicated for these envenomations per published guidelines and recommendations.Conclusions: Cottonmouth envenomations are relatively infrequent. However, they can cause significant local and systemic toxicity. Most cottonmouth envenomations in this series were treated with antivenom and were hospitalized beyond 24 hours.

California Breast Cancer Prevention Initiatives: Setting a research agenda for prevention

The environment is an underutilized pathway to breast cancer prevention. Current research approaches and funding streams related to breast cancer and the environment are unequal to the task at hand. We undertook the California Breast Cancer Prevention Initiatives, a four-year comprehensive effort to set a research agenda related to breast cancer, the environment, disparities and prevention. We identified 20 topics for Concept Proposals reflecting a life-course approach and the complex etiology of breast cancer; considering the environment as chemical, physical and socially constructed exposures that are experienced concurrently: at home, in the community and at work; and addressing how we should be modifying the world around us to promote a less carcinogenic environment. Redirecting breast cancer research toward prevention-oriented discovery could significantly reduce the incidence and associated disparities of the disease among future generations.

Occupational exposure to diesel exhaust and lung cancer: a meta-analysis

OBJECTIVES

We undertook a meta-analysis of epidemiological studies investigating the relationship between occupational diesel exhaust exposure and lung cancer.

METHODS

Thirty of 47 studies initially identified as potentially relevant met specified inclusion criteria. We extracted or calculated 39 independent estimates of relative risk and derived pooled estimates of risk for all studies and for numerous study subsets by using a random-effects model. We also examined interstudy heterogeneity by using linear metaregressions.

RESULTS

There was substantial heterogeneity in the pooled risk estimates for all studies combined and for most subsets. Several factors consistent with higher study quality, however, contributed to increased pooled estimates of risk and lower heterogeneity, including (1) adjustment for confounding by cigarette smoking and other covariates, (2) having a lower likelihood of selection bias, and (3) having increased study power.

CONCLUSION

This analysis provides quantitative support for prior qualitative reviews that have ascribed an etiologic role to occupational diesel exhaust exposure in lung cancer induction. Among study populations most likely to have had substantial exposure to diesel exhaust, the pooled smoking-adjusted relative risk was 1.47 (95% confidence interval = 1.29, 1.67).

Benzene poisoning, a risk factor for hematological malignancy, is associated with the NQO1 609C-->T mutation and rapid fractional excretion of chlorzoxazone

Benzene is a ubiquitous occupational hematotoxin and leukemogen, but people vary in their response to this toxic agent. To evaluate the impact of interindividual variation in enzymes that activate (i.e., CYP2E1) and detoxify (i.e., NQO1) benzene and its metabolites, we carried out a case-control study in Shanghai, China, of occupational benzene poisoning (BP; i.e., hematotoxicity), which we show is itself strongly associated with subsequent development of acute nonlymphocytic leukemia and the related myelodysplastic syndromes (relative risk, 70.6; 95% confidence interval, 11.4-439.3). CYP2E1 and NQO1 genotypes were determined by PCR-RFLP, and CYP2E1 enzymatic activity was estimated by the fractional excretion of chlorzoxazone (fe(6-OH)) for 50 cases of BP and 50 controls. Subjects with both a rapid fe(6-OH). and two copies of the NQO1 609C-->T mutation had a 7.6-fold (95% confidence interval, 1.8-31.2) increased risk of BP compared to subjects with a slow fe(6-OH) who carried one or two wild-type NQO1 alleles. In contrast, the CYP2E1 PstI/RsaI polymorphism did not influence BP risk. This is the first report that provides evidence of human susceptibility to benzene-related disease. Further evaluation of susceptibility for hematotoxicity and hematological malignancy among workers with a history of occupational exposure to benzene is warranted.

An epidemiologic study of early biologic effects of benzene in Chinese workers

Benzene is a recognized hematotoxin and leukemogen, but its mechanisms of action in humans are still uncertain. To provide insight into these processes, we carried out a cross-sectional study of 44 healthy workers currently exposed to benzene (median 8-hr time-weighted average; 31 ppm), and unexposed controls in Shanghai, China. Here we provide an overview of the study results on peripheral blood cells levels and somatic cell mutation frequency measured by the glycophorin A (GPA) gene loss assay and report on peripheral cytokine levels. All peripheral blood cells levels (i.e., total white blood cells, absolute lymphocyte count, platelets, red blood cells, and hemoglobin) were decreased among exposed workers compared to controls, with the exception of the red blood cell mean corpuscular volume, which was higher among exposed subjects. In contrast, peripheral cytokine levels (interleukin-3, interleukin-6, erythropoietin, granulocyte colony-stimulating factor, tissue necrosis factor-alpha) in a subset of the most highly exposed workers (n = 11) were similar to values in controls (n = 11), suggesting that benzene does not affect these growth factor levels in peripheral blood. The GPA assay measures stem cell or precursor erythroid cell mutations expressed in peripheral red blood cells of MN heterozygous subjects, identifying NN variants, which result from loss of the GPA M allele and duplication of the N allele, and N phi variants, which arise from gene inactivation. The NN (but not N phi) GPA variant cell frequency was elevated in the exposed workers compared with controls (mean +/- SD, 13.9 +/- 8.4 mutants per million cells versus 7.4 +/- 5.2 per million cells, (respectively; p = 0.0002), suggesting that benzene produces gene-duplicating but not gene-inactivating mutations at the GPA locus in bone marrow cells of exposed humans. These findings, combined with ongoing analyses of benzene macromolecular adducts and chromosomal aberrations, will provide an opportunity to comprehensively evaluate a wide range of early biologic effects associated with benzene exposure in humans.

Benzene induces gene-duplicating but not gene-inactivating mutations at the glycophorin A locus in exposed humans

Occupational exposure to benzene is known to cause leukemia, but the mechanism remains unclear. Unlike most other carcinogens, benzene and its metabolites are weakly or nonmutagenic in most simple gene mutation assays. Benzene and its metabolites do, however, produce chromosomal damage in a variety of systems. Here, we have used the glycophorin A (GPA) gene loss mutation assay to evaluate the nature of DNA damage produced by benzene in 24 workers heavily exposed to benzene and 23 matched control individuals in Shanghai, China. The GPA assay identifies stem cell or precursor erythroid cell mutations expressed in peripheral erythrocytes of MN-heterozygous subjects, distinguishing the NN and N phi mutant variants. A significant increase in the NN GPA variant cell frequency (Vf) was found in benzene-exposed workers as compared with unexposed control individuals (mean +/- SEM, 13.9 +/- 1.7 per million cells vs. 7.4 +/- 1.1 per million cells in control individuals; P = 0.0002). In contrast, no significant difference existed between the two groups for the N phi Vf (9.1 +/- 0.9 vs. 8.8 +/- 1.8 per million cells; P = 0.21). Further, lifetime cumulative occupational exposure to benzene was associated with the NN Vf (P = 0.005) but not with the N phi Vf (P = 0.31), suggesting that NN mutations occur in longer-lived bone marrow stem cells. NN variants result from loss of the GPA M allele and duplication of the N allele, presumably through recombination mechanisms, whereas NO variants arise from gene inactivation, presumably due to point mutations and deletions. Thus, these results suggest that benzene produces gene-duplicating mutations but does not produce gene-inactivating mutations at the GPA locus in bone marrow cells of humans exposed to high benzene levels. This finding is consistent with data on the genetic toxicology of benzene and its metabolites and adds further weight to the hypothesis that chromosome damage and mitotic recombination are important in benzene-induced leukemia.