Development of a Unit Risk Factor for 1,3-Butadiene Based on an Updated Carcinogenic Toxicity Assessment

The Texas Commission on Environmental Quality (TCEQ) has developed an inhalation unit risk factor (URF) for 1,3-butadiene based on leukemia mortality in an updated epidemiological study on styrene-butadiene rubber production workers conducted by researchers at the University of Alabama at Birmingham. Exposure estimates were updated and an exposure estimate validation study as well as dose-response modeling were conducted by these researchers. This information was not available to the U.S. Environmental Protection Agency when it prepared its health assessment of 1,3-butadiene in 2002. An extensive analysis conducted by TCEQ discusses dose-response modeling, estimating risk for the general population from occupational workers, estimating risk for potentially sensitive subpopulations, effect of occupational exposure estimation error, and use of mortality rates to predict incidence. The URF is 5.0 × 10⁻⁷ per μg/m³ or 1.1 × 10⁻⁶ per ppb and is based on a Cox regression dose-response model using restricted continuous data with age as a covariate, and a linear low-dose extrapolation default approach using the 95% lower confidence limit as the point of departure. Age-dependent adjustment factors were applied to account for possible increased susceptibility for early life exposure. The air concentration at 1 in 100,000 excess leukemia mortality, the no-significant-risk level, is 20 μg/m³ (9.1 ppb), which is slightly lower than the TCEQ chronic reference value of 33 μg/m³ (15 ppb) protective of ovarian atrophy. These values will be used to evaluate ambient air monitoring data so the general public is protected against adverse health effects from chronic exposure to 1,3-butadiene.     

Could Removing Arsenic from Tobacco Smoke Significantly Reduce Smoker Risks of Lung Cancer?

If a specific biological mechanism could be determined by which a carcinogen increases lung cancer risk, how might this knowledge be used to improve risk assessment? To explore this issue, we assume (perhaps incorrectly) that arsenic in cigarette smoke increases lung cancer risk by hypermethylating the promoter region of gene p16INK4a, leading to a more rapid entry of altered (initiated) cells into a clonal expansion phase. The potential impact on lung cancer of removing arsenic is then quantified using a three‐stage version of a multistage clonal expansion (MSCE) model. This refines the usual two‐stage clonal expansion (TSCE) model of carcinogenesis by resolving its intermediate or “initiated” cell compartment into two subcompartments, representing experimentally observed “patch” and “field” cells. This refinement allows p16 methylation effects to be represented as speeding transitions of cells from the patch state to the clonally expanding field state. Given these assumptions, removing arsenic might greatly reduce the number of nonsmall cell lung cancer cells (NSCLCs) produced in smokers, by up to two‐thirds, depending on the fraction (between 0 and 1) of the smoking‐induced increase in the patch‐to‐field transition rate prevented if arsenic were removed. At present, this fraction is unknown (and could be as low as zero), but the possibility that it could be high (close to 1) cannot be ruled out without further data.     

Evaluating the effectiveness of the first breast cancer awareness campaign in the United Arab Emirates: Lessons learned and next steps

Following an innovative breast cancer awareness campaign in the United Arab Emirates, a dual language survey of 500 women and in-depth interviews were conducted. The study found television advertising to be the most optimal awareness communication method, particularly among Emirati and other Arab women respondents. The research also found strong support for a year-long awareness campaign.     

Comparative Potency Method for Cancer Risk Assessment: Application to Diesel Particulate Emissions1

An estimation of the human lung cancer “unit risk” from diesel engine particulate emissions has been made using a comparative potency approach. This approach involves evaluating the tumorigenic and mutagenic potencies of the particulates from four diesel and one gasoline engine in relation to other combustion and pyrolysis products (coke oven, roofing tar, and cigarette smoke) that cause lung cancer in humans. The unit cancer risk is predicated on the linear nonthreshold extrapolation model and is the individual lifetime excess lung cancer risk from continuous exposure to 1 μg carcinogen per m³ inhaled air. The human lung cancer unit risks obtained from the epidemiologic data for coke oven workers, roofing tar applicators, and cigarette smokers were, respectively, 9.3 × 10^?4, 3.6 × 10^?4, and 2.2 × 10^?6 per μg particulate organics per m³ air. The comparative potencies of these three materials and the diesel and gasoline engine exhaust particulates (as organic extracts) were evaluated by in vivo tumorigenicity bioassays involving skin initiation and skin carcinogenicity in SENCAR mice and by the in vitro bioassays that proved suitable for this analysis: Ames Salmonella microsome bioassay, L5178Y mouse lymphoma cell mutagenesis bioassay, and sister chromatid exchange bioassay in Chinese hamster ovary cells. The relative potencies of the coke oven, roofing tar, and cigarette smoke emissions, as determined by the mouse skin initiation assay, were within a factor of 2 of those determined using the epidemiologic data. The relative potencies, from the in vitro bioassays as compared to the human data, were similar for coke oven and roofing tar, but for the cigarette smoke condensate the in vitro tests predicted a higher relative potency. The mouse skin initiation bioassay was used to determine the unit lung cancer risk for the most potent of the diesel emissions. Based on comparisons with coke oven, roofing tar, and cigarette smoke, the unit cancer risk averaged 4.4 × 10^?4. The unit lung cancer risks for the other, less potent motor-vehicle emissions were determined from their comparative potencies relative to the most potent diesel using three in vitro bioassays. There was a high correlation between the in vitro and in vivo bioassays in their responses to the engine exhaust particulate extracts. The unit lung cancer risk per μg particulates per m³ for the automotive diesel and gasoline exhaust particulates ranged from 0.20 × 10^?4 to 0.60 × 10^?4; that for the heavy-duty diesel engine was 0.02 × 10^?4. These unit risks provide the basis for a future assessment of human lung cancer risks when combined with human population exposure to automotive emissions.     

Assessment of the Effectiveness of Radon Screening Programs in Reducing Lung Cancer Mortality

The present study was aimed at assessing the health consequences of the presence of radon in Quebec homes and the possible impact of various screening programs on lung cancer mortality. Lung cancer risk due to this radioactive gas was estimated according to the cancer risk model developed by the Sixth Committee on Biological Effects of Ionizing Radiations. Objective data on residential radon exposure, population mobility, and tobacco use in the study population were integrated into a Monte‐Carlo‐type model. Participation rates to radon screening programs were estimated from published data. According to the model used, approximately 10% of deaths due to lung cancer are attributable to residential radon exposure on a yearly basis in Quebec. In the long term, the promotion of a universal screening program would prevent less than one death/year on a province‐wide scale (0.8 case; IC 99%: –3.6 to 5.2 cases/year), for an overall reduction of 0.19% in radon‐related mortality. Reductions in mortality due to radon by (1) the implementation of a targeted screening program in the region with the highest concentrations, (2) the promotion of screening on a local basis with financial support, or (3) the realization of systematic investigations in primary and secondary schools would increase to 1%, 14%, and 16.4%, respectively, in the each of the populations targeted by these scenarios. Other than the battle against tobacco use, radon screening in public buildings thus currently appears as the most promising screening policy for reducing radon‐related lung cancer.     

Diesel Engine Exhaust and Lung Cancer Mortality: Time‐Related Factors in Exposure and Risk

To develop a quantitative exposure‐response relationship between concentrations and durations of inhaled diesel engine exhaust (DEE) and increases in lung cancer risks, we examined the role of temporal factors in modifying the estimated effects of exposure to DEE on lung cancer mortality and characterized risk by mine type in the Diesel Exhaust in Miners Study (DEMS) cohort, which followed 12,315 workers through December 1997. We analyzed the data using parametric functions based on concepts of multistage carcinogenesis to directly estimate the hazard functions associated with estimated exposure to a surrogate marker of DEE, respirable elemental carbon (REC). The REC‐associated risk of lung cancer mortality in DEMS is driven by increased risk in only one of four mine types (limestone), with statistically significant heterogeneity by mine type and no significant exposure‐response relationship after removal of the limestone mine workers. Temporal factors, such as duration of exposure, play an important role in determining the risk of lung cancer mortality following exposure to REC, and the relative risk declines after exposure to REC stops. There is evidence of effect modification of risk by attained age. The modifying impact of temporal factors and effect modification by age should be addressed in any quantitative risk assessment (QRA) of DEE. Until there is a better understanding of why the risk appears to be confined to a single mine type, data from DEMS cannot reliably be used for QRA.     

Reanalysis of the DEMS Nested Case‐Control Study of Lung Cancer and Diesel Exhaust: Suitability for Quantitative Risk Assessment

The International Agency for Research on Cancer (IARC) in 2012 upgraded its hazard characterization of diesel engine exhaust (DEE) to “carcinogenic to humans.” The Diesel Exhaust in Miners Study (DEMS) cohort and nested case‐control studies of lung cancer mortality in eight U.S. nonmetal mines were influential in IARC's determination. We conducted a reanalysis of the DEMS case‐control data to evaluate its suitability for quantitative risk assessment (QRA). Our reanalysis used conditional logistic regression and adjusted for cigarette smoking in a manner similar to the original DEMS analysis. However, we included additional estimates of DEE exposure and adjustment for radon exposure. In addition to applying three DEE exposure estimates developed by DEMS, we applied six alternative estimates. Without adjusting for radon, our results were similar to those in the original DEMS analysis: all but one of the nine DEE exposure estimates showed evidence of an association between DEE exposure and lung cancer mortality, with trend slopes differing only by about a factor of two. When exposure to radon was adjusted, the evidence for a DEE effect was greatly diminished, but was still present in some analyses that utilized the three original DEMS DEE exposure estimates. A DEE effect was not observed when the six alternative DEE exposure estimates were utilized and radon was adjusted. No consistent evidence of a DEE effect was found among miners who worked only underground. This article highlights some issues that should be addressed in any use of the DEMS data in developing a QRA for DEE.     

EEFSEC基因、染色体17q24和染色体11q13.2基因变异与前列腺癌的关联研究

目的探索EEFSEC基因(rs10934853,A)、染色体17q24区(rs1859962,T)和染色体11q13.2(rs7931342,T)的基因变异类型与前列腺癌患病发病风险的关联,分析这些基因型与前列腺癌患者临床特征的关系。方法采用病例对照研究设计,比较病例组中124例患者和对照组中138例正常对照者的EEFSEC基因(rs10934853,A)、染色体17q24区(rs1859962,T)和染色体11q13.2(rs7931342,T)等位基因和基因型频率的差异,并探讨各基因变异与患者的确诊年龄,BMI,Gleason评分,PSA浓度,肿瘤分期等临床特征之间的关联。结果 EEFSEC基因(rs10934853,A)、染色体17q24区(rs1859962,T)和染色体11q13.2(rs7931342,T)的基因型和等位基因在病例组和对照组中的频率分布差异均无统计学意义(P0.05),然而,EEFSEC基因(rs10934853,A)和染色体17q24区(rs1859962,T)存在更强的基因-基因协同的交互作用(P=0.0396,OR=1.722,95%CI=1.0244~2.8944);病例组基因型-表型观察指标关联分析表明,3个SNPs与PCa患者的年龄、Gleason评分、PSA浓度及烟酒均无关联(P0.05),然而,染色体17q24区(rs1859962,T)位点与食用蛋类有关(P=0.005)。结论 EEFSEC基因(rs10934853,A),17q24(rs1859962,T)和11q13.2(rs7931342,T)位点可能与我国北方人群前列腺癌的发病风险无关联,但是存在有基因之间增加PCa发病风险的协同效应。     

TP与GP化疗方案对肺癌患者骨髓抑制影响的Meta分析

目的通过Meta分析对紫杉醇+顺铂(TP)与吉西他滨+顺铂(GP)化疗方案对肺癌抗肿瘤药物治疗患者骨髓抑制的影响进行系统分析,探讨TP和GP的骨髓抑制差别。方法通过荟萃分析对TP与GP的骨髓抑制研究进行同质性检验和合并效应量的估计。结果同质性检验:χ2=91.84,自由度为29,P0.00001;合并效应量的估计:OR合并=1.36,OR合并95%可信限为0.90~2.04。OR合并的检验Z=1.482.41,P=0.14。结论 TP与GP化疗时对患者的骨髓抑制不良反应情况没有本质区别。     

TKI治疗老年晚期非小细胞肺癌的临床研究

目的进行吉非替尼治疗老年晚期非小细胞肺癌的疗效和毒性反应的临床研究。方法 102例晚期非小细胞肺癌,其中52例给予吉非替尼150mg口服,每日1次,每28天重复。50例予单药吉西他滨1000mg/m2,d1,d8,d15,每28天重复。结果吉非替尼组CR、PR、SD、有效率、疾病控制率、1年生存率分别为3.85%,21.15%,38.46%,38.46%,25.00%,64.50%和28.85%。吉西他滨组CR、PR、SD、有效率、疾病控制率、1年生存率分别为0,24%,32%,24%,56%和26%。两者之间无统计学差异。吉非替尼治疗常见的毒副作用为皮疹和腹泻,总的皮疹发生率为46.15%,腹泻发生率为26.9%,未见间质性肺病和常见的血液学毒性出现。而吉西他滨组的不良反应主要为骨髓抑制和消化道反应。在血液学毒性方面吉西他滨明显高于吉非替尼组,具有统计学差异(P0.05)。结论吉非替尼和吉西他滨单药治疗老年非小细胞肺癌疗效确切并相当。吉非替尼不仅延长了患者的生存,而且不良反应较轻,值得在临床老年非小细胞肺癌中应用。