Systematic evidence map (SEM) template: Report format and methods used for the US EPA Integrated Risk Information System (IRIS) program, Provisional Peer Reviewed Toxicity Value (PPRTV) program, and other "fit for purpose" literature-based human health analyses.

Background: Systematic evidence maps (SEMs) are gaining visibility in environmental health for their utility to serve as problem formulation tools and assist in decision-making, especially for priority setting. SEMs are now routinely prepared as part of the assessment development process for the US Environmental Protection Agency (EPA) Integrated Risk Information System (IRIS) and Provisional Peer Reviewed Toxicity Value (PPRTV) assessments. SEMs can also be prepared to explore the available literature for an individual chemical or groups of chemicals of emerging interest.

Use of systematic evidence maps within the US environmental protection agency (EPA) integrated risk information system (IRIS) program: Advancements to date and looking ahead.

Systematic evidence maps (SEMs) are increasingly used to inform decision-making and risk management priority-setting and to serve as problem formulation tools to refine the focus of questions that get addressed in full systematic reviews. Within the U.S.

Health Effects of Naphthalene Exposure: A Systematic Evidence Map and Analysis of Potential Considerations for Dose-Response Evaluation.

Background: Naphthalene is a polycyclic aromatic hydrocarbon that has been associated with health effects, including cancer. As the state of the science on naphthalene toxicity continues to evolve, updated toxicity reference value(s) may be required to support human health risk assessment.

Objectives: We present a systematic evidence map of studies that could be used to derive toxicity reference value(s) for naphthalene.

Application of systematic evidence mapping to assess the impact of new research when updating health reference values: A case example using acrolein.

Background: The environmental health community needs transparent, methodologically rigorous, and rapid approaches for updating human health risk assessments. These assessments often contain reference values for cancer and/or noncancer effects. Increasingly, the use of systematic review methods are preferred when developing these assessments.

Carcinogenicity of ethylene oxide: key findings and scientific issues.

In support of the Integrated Risk Information System (IRIS), the U.S. Environmental Protection Agency (EPA) completed an evaluation of the inhalation carcinogenicity of ethylene oxide (EtO) in December 2016.

A framework and case studies for evaluation of enzyme ontogeny in children's health risk evaluation.

Knowledge of the ontogeny of Phase I and Phase II metabolizing enzymes may be used to inform children's vulnerability based upon likely differences in internal dose from xenobiotic exposure. This might provide a qualitative assessment of toxicokinetic (TK) variability and uncertainty pertinent to early lifestages and help scope a more quantitative physiologically based toxicokinetic (PBTK) assessment. Although much is known regarding the ontogeny of metabolizing systems, this is not commonly utilized in scoping and problem formulation stage of human health risk evaluation.

Laboratory to community: chemoprevention is the answer.

In the current issue, Johnson and colleagues present exciting results, using biomarkers involved in aflatoxin B1 (AFB1)-induced hepatocarcinogenesis, as an example of a conceptual framework to target mechanisms of action in developing chemopreventive agents. Their innovative approach offers considerable promise for a field that has long been neglected. Proof-of-principle was demonstrated using a synthetic triterpenoid (CDDO-Im), which activates Nrf2 signal transduction pathway, inhibits formation of AFB1-induced DNA adducts and neoplastic hepatic foci, and alters the expression of genes associated with aflatoxin-mediated toxicity.

Association of body burden of mercury with liver function test status in the U.S. population.

The majority of mercury (Hg) exposure in the US population is from consumption of fish contaminated with methylmercury (MeHg). Since inorganic Hg is the predominant form excreted in the feces and urine, hepatic biotransformation is a critical step in its normal clearance. This study was set to test the hypothesis that compromised liver function is associated with body burden of Hg as indirectly reflected by Hg sampled in blood and urine.

The use of genetically modified mice in cancer risk assessment: challenges and limitations.

The use of genetically modified (GM) mice to assess carcinogenicity is playing an increasingly important role in the safety evaluation of chemicals. While progress has been made in developing and evaluating mouse models such as the Trp53⁺/⁻, Tg.AC and the rasH2, the suitability of these models as replacements for the conventional rodent cancer bioassay and for assessing human health risks remains uncertain.

Dose-response analysis of bromate-induced DNA damage and mutagenicity is consistent with low-dose linear, nonthreshold processes.

Mutagenic agents have long been inferred to act through low-dose linear, nonthreshold processes. However, there is debate about this assumption, with various studies interpreting datasets as showing thresholds for DNA damage and mutation. We have applied rigorous statistical analyses to investigate the shape of dose-response relationships for a series of in vitro and in vivo genotoxicity studies using potassium bromate (KBrO(3) ), a water ozonation byproduct that is bioactivated to a reactive species causing oxidative damage to DNA.

The potential of metabolomic approaches for investigating mode(s) of action of xenobiotics: case study with carbon tetrachloride.

Both experimental animals and humans exhibit complex cellular responses upon exposure to xenobiotics and may undergo similar types of metabolic changes leading to adverse outcomes. Exposure to xenobiotics results in perturbation of many cellular events (e.g.

Effects of mainstream cigarette smoke on the global metabolome of human lung epithelial cells.

Metabolomics is a technology for identifying and quantifying numerous biochemicals across metabolic pathways. Using this approach, we explored changes in biochemical profiles of human alveolar epithelial carcinoma (A549) cells following in vitro exposure to mainstream whole smoke (WS) aerosol as well as to wet total particulate matter (WTPM) or gas/vapor phase (GVP), the two constituent phases of WS from 2R4F Kentucky reference cigarettes. A549 cells were exposed to WTPM or GVP (expressed as WTPM mass equivalent GVP volumes) at 0, 5, 25, or 50 microg/mL or to WS from zero, two, four, and six cigarettes for 1 or 24 h.

Role of cytochrome p4501 family members in the metabolic activation of polycyclic aromatic hydrocarbons in mouse epidermis.

Polycyclic aromatic hydrocarbons (PAHs) are known to be activated by the cytochrome P450 (P450) 1 family. However, the precise role of individual P4501 family members in PAH bioactivation remains to be fully elucidated. We therefore investigated the formation of PAH-DNA adducts in the epidermis of Cyp1a2(-/-), Cyp1b1(-/-), and Ahr(-/-) knockout mice.

High levels of oxidative DNA damage in lymphocyte DNA of premenopausal breast cancer patients from Egypt.

Egypt shows a parallel increase in premenopausal breast cancer and environmental pollution. The purpose of this study is to explore a possible relationship between oxidative DNA damage, urinary estrogen metabolites and breast cancer in Egyptian premenopausal women. We conducted a pilot study of Egyptian breast cancer involving 29 cases and 32 controls and analysed lymphocyte DNA levels of 7,8-dihydro-8-oxo-2'-deoxyguanine (8-oxo-dG), a measure of oxidative DNA damage using high performance liquid chromatography with electro-chemical detection (HPLC-ECD) method.

Serum organochlorine levels and history of lactation in Egypt.

We conducted a study in Egypt to assess the determinants of organochlorine serum levels among premenopausal women and the risk of premenopausal breast cancer for women with high organochlorine serum levels. We included 69 breast cancer patients and 53 controls consisting of visitors to the hospitals of the cancer patients. We found low levels of dichlorodiphenyldichloroethylene (DDE), total dichlorodiphenyltrichloroethane, and beta-hexacholorhexane (beta-HCH) in most subjects.

The effect of plant phenolics on the formation of 7,12-dimethylbenz[a]anthracene-DNA adducts and TPA-stimulated polymorphonuclear neutrophils chemiluminescence in vitro.

Phenolics, common plant constituents, form up an important part of human diet and are considered potential chemopreventive agents. In the present study, structurally diverse phenolics, such as tannic acid, protocatechuic acid, chlorogenic acid and resveratrol, were investigated for their inhibitory effects on covalent binding of 7,12-dimethylbenz[a]anthracene (DMBA) to DNA in vitro and the suppression of oxidative burst in 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated human polymorphonuclear neutrophils (PMNs). 32P-postlabeling analysis of DNA incubated with DMBA in the presence of 3-methylcholanthrene (3-MC)-induced microsomes produced three major adducts derived from anti-, syn- and anti-dihydrodiol epoxides through reactions with dGuo and dAdo, respectively.

Oral administration of the citrus coumarin, isopimpinellin, blocks DNA adduct formation and skin tumor initiation by 7,12-dimethylbenz[a]anthracene in SENCAR mice.

The current study was designed to evaluate the effects of oral administration of the citrus coumarin, isopimpinellin, on skin tumor initiation by topically applied benzo[a]pyrene (B[a]P) and 7,12-dimethylbenz[a]anthracene (DMBA). To evaluate the effects of orally administered isopimpinellin on skin tumor initiation by B[a]P and DMBA, its effects on DNA adduct formation were first evaluated. Female SENCAR mice were pre-treated twice with corn oil, or isopimpinellin (70 mg/kg body wt per os) at 24 h and 2 h prior to topical treatment with B[a]P or DMBA.

Characterization of a major aromatic DNA adduct detected in human breast tissues.

A bulky DNA adduct (Spot 1) was previously detected in normal adjacent breast tissues of 41% (36/87) of women with breast cancer and in none (0/29) of the noncancer controls by (32)P-postlabeling. To characterize this adduct, it was chromatographically compared with DNA adduct profiles generated in several in vitro and in vivo experimental systems. First, MCF-7 cells were exposed to a number of chemical carcinogens, that is, benzo[a]pyrene (B[a]P), 4-OH-B[a]P, 9-OH-B[a]P, 11-OH-B[a]P, B[a]P-trans-4,5-dihydrodiol, 1-nitropyrene, 6-nitrochrysene, dibenzo[a,l]pyrene, benzo[c]phenanthrene, dibenzo[a,h]anthracene, 3-methylcholanthrene, and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine.

Role of cytochrome P450 1a1 and 1b1 in the metabolic activation of 7,12-dimethylbenz[a]anthracene and the effects of naturally occurring furanocoumarins on skin tumor initiation.

The current study was designed to determine the mechanistic basis for differences in the effects of naturally occurring furanocoumarins on skin tumor initiation by 7,12-dimethylbenz[a]anthracene (DMBA). Female SENCAR mice were pretreated topically with bergamottin, imperatorin, or isopimpinellin (100-3200 nmol), 7,8-benzoflavone (7,8-BF, 5-40 nmol, a known inhibitor of DMBA skin carcinogenesis in mice), or acetone (vehicle control) 5 min prior to topical treatment with DMBA (10 nmol). Imperatorin, isopimpinellin, and 7,8-BF, but not bergamottin, significantly blocked total DMBA-DNA adduct formation.

Oral administration of naturally occurring coumarins leads to altered phase I and II enzyme activities and reduced DNA adduct formation by polycyclic aromatic hydrocarbons in various tissues of SENCAR mice.

Several naturally occurring coumarins, to which humans are routinely exposed in the diet, were previously found to inhibit P450-mediated metabolism of benzo[a]pyrene (B[a]P) and 7,12-dimethylbenz[a]anthracene (DMBA) in vitro, block DNA adduct formation in mouse epidermis and inhibit skin tumor initiation by B[a]P and/or DMBA when applied topically to mice. The present study was designed to investigate the effects of two of these compounds, of the linear furanocoumarin type, when given orally (70 mg/kg per os, four successive daily doses), on P450 and glutathione S-transferase (GST) activities and DNA adduct formation by B[a]P and DMBA in various mouse tissues. Imperatorin and isopimpinellin significantly blocked ethoxyresorufin O-deethylase (EROD) and pentoxyresorufin O:-dealkylase (PROD) activities in epidermis at 1 and 24 h after oral dosing.

Both (+/-)syn- and (+/-)anti-7,12-dimethylbenz[a]anthracene-3,4-diol-1,2-epoxides initiate tumors in mouse skin that possess -CAA- to -CTA- mutations at Codon 61 of c-H-ras.

We have determined the tumor-initiating activity of (+/-)syn- and (+/-)anti-7,12-dimethylbenz[a]anthracene-3,4-diol-1,2-epoxide (syn- and anti-DMBADE), the two metabolically formed bay-region diol epoxides of DMBA, and we have also analyzed mutations in the H-ras gene from tumors induced by these compounds. Using a two-stage, initiation-promotion protocol for tumorigenesis in mouse skin, we have found that both syn- and anti-DMBADE are active tumor initiators, and that the occurrence of papillomas is carcinogen dose dependent. All of the papillomas induced by syn-DMBADE (a total of 40 mice), 96% of those induced by anti-DMBADE (a total of 25 mice), and 94% of those induced by DMBA (a total of 16 mice) possessed a -CAA- to -CTA- mutation at codon 61 of H-ras.

Characterization of the major DNA adducts in the liver of rats chronically exposed to tamoxifen for 18 months.

Our previous study has shown that chronic exposure to tamoxifen (TAM) induced formation of high levels of DNA adducts in the liver, the target tissue of TAM-induced carcinogenesis in rats. One of the major DNA adducts (spot 1), as detected by 32P-postlabeling, accounted for 53% of the total adducts. To characterize this major adduct, the current study has compared spot 1 with two previously identified TAM-DNA adducts, i.