Exposure variability in the workplace: its implications for the assessment of compliance

Day-to-day variations of occupational exposures have important implications for the industrial hygienist trying to assess compliance with an occupational exposure limit. As only a limited number of samples are taken during an observation period, extrapolations are required to estimate exposures over the unsampled period. Compliance may be evaluated using estimates of the geometric mean (GM) and the geometric standard deviation (GSD) to calculate a confidence interval around the mean exposure and compare this interval to a limit value, assuming a lognormal distribution of exposures over time. These confidence intervals are very sensitive to the estimate of GSD. Hence, the questions of when to sample and how many samples to take for a reliable assessment of exposure variability (GSD) are the focus of this paper. Analyses of simulated exposure-time series and 420 data sets of personal exposures with three or more measurements obtained from actual workplaces demonstrate that the small number of samples usually collected during surveys leads to biased estimates of the variance of the exposure distribution. There is a high likelihood of an underestimate of variance, which rapidly increases if 8-hr time-weighted average samples are collected on consecutive days or within a week. The results indicate that in 80% of the within-week exposure-time series, the estimated GSD may be too low, even up to a factor of 2. Evidence is presented that autocorrelation is a likely explanation for the bias observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exposure to secondhand smoke in the workplace: serum cotinine by occupation

To examine workplace exposure to secondhand smoke by occupation, we analyzed data from The Third National Health and Nutrition Examination Survey (NHANES III) (1988 to 1994), a nationally representative sample of the noninstitutionalized population. The analysis was restricted to 4952 employed nonsmoking adults who reported no home exposure to cigarette smoke. Occupations were assigned to 40 groups and 7 categories. Among the categories, geometric mean serum cotinine (ng/mL) ranged from 0.09 for farming/forestry/fishing occupations to 0.22 for operators/fabricators/laborers (median, 0.16). The lowest values were observed among farmers and nursery workers (0.06) and the highest among waiters (0.47). Between 1988 to 1991 and 1991 to 1994, the overall geometric mean cotinine and the proportion reporting that they could smell smoke at work decreased significantly. In conclusion, workplace exposure to secondhand smoke varied by occupation, and decreases in exposure occurred between 1988 to 1991 and 1991 to 1994.     

Induction of inflammation in vascular endothelial cells by metal oxide nanoparticles: effect of particle composition

BACKGROUND: The mechanisms governing the correlation between exposure to ultrafine particles and the increased incidence of cardiovascular disease remain unknown. Ultrafine particles appear to cross the pulmonary epithelial barrier into the bloodstream, raising the possibility of direct contact with the vascular endothelium. OBJECTIVES: Because endothelial inflammation is critical for the development of cardiovascular pathology, we hypothesized that direct exposure of human aortic endothelial cells (HAECs) to ultrafine particles induces an inflammatory response and that this response depends on particle composition. METHODS: To test the hypothesis, we incubated HAECs for 1-8 hr with different concentrations (0.001-50 mug/mL) of iron oxide (Fe(2)O(3)), yttrium oxide (Y(2)O(3)), and zinc oxide (ZnO) nanoparticles and subsequently measured mRNA and protein levels of the three inflammatory markers intra-cellular cell adhesion molecule-1, interleukin-8, and monocyte chemotactic protein-1. We also determined nanoparticle interactions with HAECs using inductively coupled plasma mass spectrometry and transmission electron microscopy. RESULTS: Our data indicate that nanoparticle delivery to the HAEC surface and uptake within the cells correlate directly with particle concentration in the cell culture medium. All three types of nanoparticles are internalized into HAECs and are often found within intracellular vesicles. Fe(2)O(3) nanoparticles fail to provoke an inflammatory response in HAECs at any of the concentrations tested; however, Y(2)O(3) and ZnO nanoparticles elicit a pronounced inflammatory response above a threshold concentration of 10 mug/mL. At the highest concentration, ZnO nanoparticles are cytotoxic and lead to considerable cell death. CONCLUSIONS: These results demonstrate that inflammation in HAECs following acute exposure to metal oxide nanoparticles depends on particle composition.     

Genotoxicity of metal nanoparticles

Nanotechnology is currently used in industry, medicine, and military applications, as well as in more than 300 commercial products. Yet, the same properties that make these particles exciting for technology also make them daunting public health concerns because their toxicity is unknown and relatively unexplored. Increased attention is being placed on the study of metal particle genotoxicity; however, a lot of unknowns remain about their effects and the mechanisms. In this article, we highlight some metal and metal oxide nanoparticles of interest and discuss the current in vivo and in vitro studies of genotoxic effects. Many metal nanoparticles were found to cause chromosomal aberrations, DNA strand breaks, oxidative DNA damage, and mutations. Inconsistencies are found in the literature, however, thus drawing conclusions is difficult due to a variety of factors. Therefore, the areas requiring further attention are highlighted and recommendations to improve our understanding of the genotoxic potential are addressed.     

Exposure to refractory ceramic fibres in the metal industry

Refractory ceramic fibres (RCF) are used in thermal isolation in the metal industry where high temperatures are regularly employed. Asbestos materials were earlier commonly used for these purposes. In this work, two Finnish steel plants, three foundries and a repair shop were studied for the ceramic fibre exposure of their workers under normal production and during the replacement of oven insulation. Personal and stationary sampling was used together with a novel nasal lavage sampling for the evaluation of personal exposure. Fibres were counted with optical and electron microscopy and they were identified using an energy-dispersive X-ray analyser. Ceramic fibres were found in most production phases [range <0.01-0.29 fibres per cubic centimetre (f cm(-3))]. Considerably higher fibre counts were obtained during the maintenance work (range <0.01-14.2 f cm(-3)). Nasal sampling was found to correlate with the airborne fibre concentrations at the group level. The mean fibre concentrations varied from 34 to 6680 f ml(-1) of lavage liquid. Use of personal respiratory protectors diminished the exposure on the average as analysed in the lavage specimens, but the effect of respirator use did not appear clearly in the results. Because of the heat conditions, the workers used the respirators for a strict minimum period. A considerable exposure to RCF occurs in the studied plants. Its risk should be evaluated and managed more closely in view that the material is carcinogenic. Use of personal respiratory protectors should be encouraged. Their effective use could be verified by the nasal sampling for fibres after the work shift.     

车间空气中氧化镉对晶状体的影响

镉毒性研究的人群资料较缺乏.我们测定了2个工厂空气中氧化镉的浓度及作业工人的尿镉含量,并对作业工人眼部晶状体损伤情况进行了检查,以探讨氧化镉粉尘对作业工人晶状体的影响.     

工作场所空气中异亚丙基丙酮的溶剂解吸气相色谱测定方法

目的 研究建立工作场所空气中异亚丙基丙酮的溶剂解吸气相色谱测定方法.方法 用活性炭采样管采样,二硫化碳(CS2)解吸,DB-WAX毛细管柱分离,氢火焰离子化检测器(FID)检测.结果 在选定实验条件下,异亚丙基丙酮在0.015～3.600 s/L之间线性关系良好,相关系数(r)=0.999 7;日内精密度为0.40%～2.06%,日间精密度为1.18%～2.24%;加标回收率为96.36%～110.70%(n=18);方法检出限为0.001 87g/L;最低检出浓度为0.623 mg/m3(以采样体积3.0 L空气计);采样效率为98.21%～99.50%;解吸效率为87.96%～93.86%;穿透容量为4 h 11.29 mg(100 mg活性炭);样品稳定性为4℃下第10天样品下降率为3.1%.结论 该方法线性范围宽,灵敏度高,精密度、准确度好,样品采集简便,采样结果稳定,达到工作场所空气中有毒物质检测方法的研制规范要求,适用于工作场所空气中异亚丙基丙酮浓度的监测.     

NIOSH field studies team assessment: Worker exposure to aerosolized metal oxide nanoparticles in a semiconductor fabrication facility

The ubiquitous use of engineered nanomaterials—particulate materials measuring approximately 1–100 nanometers (nm) on their smallest axis, intentionally engineered to express novel properties—in semiconductor fabrication poses unique issues for protecting worker health and safety. Use of new substances or substances in a new form may present hazards that have yet to be characterized for their acute or chronic health effects. Uncharacterized or emerging occupational health hazards may exist when there is insufficient validated hazard data available to make a decision on potential hazard and risk to exposed workers under condition of use. To advance the knowledge of potential worker exposure to engineered nanomaterials, the National Institute for Occupational Safety and Health Nanotechnology Field Studies Team conducted an on-site field evaluation in collaboration with on-site researchers at a semiconductor research and development facility on April 18–21, 2011. The Nanomaterial Exposure Assessment Technique (2.0) was used to perform a complete exposure assessment. A combination of filter-based sampling and direct-reading instruments was used to identify, characterize, and quantify the potential for worker inhalation exposure to airborne alumina and amorphous silica nanoparticles associated with th e chemical mechanical planarization wafer polishing process. Engineering controls and work practices were evaluated to characterize tasks that might contribute to potential exposures and to assess existing engineering controls. Metal oxide structures were identified in all sampling areas, as individual nanoparticles and agglomerates ranging in size from 60 nm to >1,000 nm, with varying structure morphology, from long and narrow to compact. Filter-based samples indicated very little aerosolized material in task areas or worker breathing zone. Direct-reading instrument data indicated increased particle counts relative to background in the wastewater treatment area; however, particle counts were very low overall, indicating a well-controlled working environment. Recommendations for employees handling or potentially exposed to engineered nanomaterials include hazard communication, standard operating procedures, conservative ventilation systems, and prevention through design in locations where engineered nanomaterials are used or stored, and routine air sampling for occupational exposure assessment and analysis.     

金属纳米颗粒神经发育毒性研究进展

随着纳米技术的飞速发展,金属纳米颗粒在不同行业的广泛应用,越来越多的研究开始关注其生物安全性。经母体暴露后,金属纳米颗粒因其独特的理化性质,可穿过胎盘屏障和血脑屏障,到达子代中枢神经系统并影响其发育。大量研究表明大脑是金属纳米颗粒作用的重要靶器官之一,其中损伤最严重的大脑区域是海马区。     

Exposure to metal fume and infectious pneumonia

To test the hypothesis that inhalation of metal fume reversibly increases susceptibility to pneumonia, the authors conducted a case-control study. Men aged 20-64 years, admitted to 11 hospitals in West Midlands, England, with community-acquired pneumonia during 1996-1999 were interviewed about their lifetime occupational history, exposure to metal fume, and potential confounding factors. Similar information was collected from controls admitted to the same hospitals with nonrespiratory illness. For cases, exposures were timed relative to the onset of their illness (on average, 6 months before interview). Exposure histories for controls were censored 6 months before interview. Interviews were completed by 525 cases and 1,122 controls (response rates of 74% and 99%). Pneumonia was associated with reported occupational exposure to metal fume in the previous year (adjusted odds ratio (OR) = 1.6, 95% confidence interval (CI): 1.1, 2.4) but not in earlier periods (OR = 1.1). The risk was highest for lobar pneumonia and recent exposure to ferrous fume (OR = 2.3, 95% CI: 1.2, 4.3). The association was not specific to any one microorganism. These findings support the hypothesis that ferrous and possibly other metal fumes reversibly predispose to infectious pneumonia. Research should now focus on the underlying mechanisms and prevention.     

微波消解原子吸收光谱法检测车间空气中的氧化锌

目的建立微波消解原子吸收光谱法测定车间空气中氧化锌浓度的方法。方法采用微波消解前处理微孔滤膜,在最佳仪器条件下用原子吸收光谱法测定氧化锌含量。结果锌浓度在0~1.00 mg/L范围内时线性关系良好,r=0.998 9,相对标准偏差1.9%~2.6%,加标回收率为95.0%,最低检出限为0.025 mg/L,最低检出浓度为0.008 mg/m~3。结论该方法精密度和准确度可满足试验要求,适用于车间空气中氧化锌含量测定。     

金属隔室作业场所工人微波辐射的暴露水平

目的　研究金属隔室作业场所微波辐射暴露水平及其防护技术。方法　按GB10 4 36 89测试方法 ,测定药品生产车间改造前用混凝土砖墙和改造后用金属板材料建造的微波隔室作业场所的漏能情况 ,评价其暴露水平及辐射控制效果。结果　作业场所改造前、后距场源 10cm处漏能平均值分别为 6 0 6 .0、10 33.0 μW/cm2 ,距场源 10 0cm处平均值分别为 79.8、5 2 .3μW/cm2 ,距场源 15 0～ 5 0 0cm处平均值分别为9.3、2 0 .5 μW/cm2 。2种不同屏蔽环境作业场所工人作业范围微波辐射暴露水平差异不大 ,漏能衰减与场源距离关系较大。场源屏蔽所采取的技术不完善 ,漏能控制效果不佳。结论　以金属材料封闭隔室的微波作业场所辐射暴露水平及防护控制问题应引起重视。     

北京市居民饮用水中16种金属元素暴露水平

目的了解北京市居民饮用水中16种金属元素(铅Pb、镉Cd、铜Cu、锌Zn、铁Fe、锰Mn、镍Ni、银Ag、锑Sb、硒Se、铝Al、钡Ba、铍Be、铊Tl、钼Mo和钠Na)暴露水平。方法采用多阶段整群抽样设计,在北京市18个区县随机抽取5个区的270户,采用电感耦合等离子体质谱法,对枯水期、丰水期居民饮用水中16种金属指标进行监测。结果居民饮用水中16种元素的暴露水平由低到高可以分为3层:Ag、Cd、Sb、Be和Tl暴露水平为:未检出～0.083μg/L,Mo、Pb、Ni和Se暴露水平为:0.06～100μg/L,Cu、Al、Zn、Mn、Fe、Na和Ba暴露水平为:0.00036～6.579mg/L。统计表明,11种元素(Pb、Se、Mo、Cu、Zn、Mn、Ni、Al、Ba、Fe和Na)暴露水平枯水期明显高于丰水期(P<0.05),以《生活饮用水卫生标准》GB5749—2006中的标准值为评价标准,枯水期Na、Al、Mn、Zn、Fe、Ba、Pb、Se的合格率为87.4%～98.9%;丰水期Mn、Ni、Zn、Fe、Pb和Se的合格率为95.2%～99.6%,其他元素合格率为100%。来自市政水源的饮用水中8种元素(Pb、Cu、Zn、Mn、Al、Ba、Fe和Na)的暴露水平明显低于来自自备水源的饮用水(P<0.05)。结论北京市居民饮用水中16种金属元素总体处于低暴露水平,大部分指标市政供水好于自备水源供水。     

Exposure to workplace noise and the risk of cardiovascular disease events and mortality among older adults

Background

We aimed to examine whether cross-sectional (prevalence) and longitudinal relationships (5-year incidence and 10-year mortality) exist between workplace noise exposure and cardiovascular diseases (CVD).

Methods

2942 participants aged 55+ years of the Blue Mountains Eye Study, Australia (1997–9 and 2002–4). Participants self-reported workplace noise exposure, hearing protector use and physician diagnosed CVD. CVD deaths were confirmed using the Australian National Death Index.

Results

133 and 937 participants self-reported workplace noise exposure, and use or non-use of hearing protection devices, respectively. After multivariate adjustment, those who did not use hearing protection devices were 53% and 75% more likely to have prevalent CVD and angina, respectively, compared to those never exposed to workplace noise. Exposure to severe workplace noise for less than 1 to 5 years versus no exposure was associated with incident stroke OR 3.44 (95% CI 1.11–10.63). The mortality rate of CVD was 0.94% per year in people unexposed to workplace noise. Participants reporting less than 1 to 5 years versus those with no workplace noise exposure had a higher risk of CVD mortality, hazard ratio, HR, 1.60 (95% CI 1.10–2.33).

Discussion

These data highlight the public health impact of workplace noise exposure on the vascular health of older adults.     

Exposure to exhaled nitrous oxide in hospitals post-anesthesia care units

Due to the present evidence for reproductive toxicity of nitrous oxide (N(2)O) among female personnel in health care, exposure of 17 female workers employed in two post-anesthesia care units was evaluated. Geometric mean concentration of nitrous oxide for six recovery room personnel was 3.1 ppm versus 1.17 ppm for eleven employees in surgical nursing units. The longest time needed to reach zero concentration of nitrous oxide in postoperative nursing units was 9.5 h. The result of correlation analysis did neither show any association between duration of nitrous oxide exhaled from patients and patient-related factors. It is very unlikely that these low exposure levels can cause any adverse health effect among pregnant PACU employees. However, for those institutions that seek extra protective measures, reassignment of pregnant employees needs to be extended for several hours after a patient is admitted in the PACU units.     

Exposure to silver nanoparticles inhibits selenoprotein synthesis and the activity of thioredoxin reductase

Background: Silver nanoparticles (AgNPs) and silver (Ag)-based materials are increasingly being incorporated into consumer products, and although humans have been exposed to colloidal Ag in many forms for decades, this rise in the use of Ag materials has spurred interest into their toxicology. Recent reports have shown that exposure to AgNPs or Ag ions leads to oxidative stress, endoplasmic reticulum stress, and reduced cell proliferation. Previous studies have shown that Ag accumulates in tissues as silver sulfides (Ag₂S) and silver selenide (Ag₂Se).Objectives: In this study we investigated whether exposure of cells in culture to AgNPs or Ag ions at subtoxic doses would alter the effective metabolism of selenium, that is, the incorporation of selenium into selenoproteins.Methods: For these studies we used a keratinocyte cell model (HaCat) and a lung cell model (A549). We also tested (in vitro, both cellular and chemical) whether Ag ions could inhibit the activity of a key selenoenzyme, thioredoxin reductase (TrxR).Results: We found that exposure to AgNPs or far lower levels of Ag ions led to a dose-dependent inhibition of selenium metabolism in both cell models. The synthesis of protein was not altered under these conditions. Exposure to nanomolar levels of Ag ions effectively blocked selenium metabolism, suggesting that Ag ion leaching was likely the mechanism underlying observed changes during AgNP exposure. Exposure likewise inhibited TrxR activity in cultured cells, and Ag ions were potent inhibitors of purified rat TrxR isoform 1 (cytosolic) (TrxR1) enzyme.Conclusions: Exposure to AgNPs leads to the inhibition of selenoprotein synthesis and inhibition of TrxR1. Further, we propose these two sites of action comprise the likely mechanism underlying increases in oxidative stress, increases endoplasmic reticulum stress, and reduced cell proliferation during exposure to Ag.     

Genotoxicity of metal nanoparticles: focus on in vivo studies

With increasing production and application of a variety of nanomaterials (NMs), research on their cytotoxic and genotoxic potential grows, as the exposure to these nano-sized materials may potentially result in adverse health effects. In large part, indications for potential DNA damaging effects of nanoparticles (NPs) originate from inconsistent in vitro studies. To clarify these effects, the implementation of in vivo studies has been emphasised. This paper summarises study results of genotoxic effects of NPs, which are available in the recent literature. They provide indications that some NP types cause both DNA strand breaks and chromosomal damages in experimental animals. Their genotoxic effects, however, do not depend only on particle size, surface modification (particle coating), and exposure route, but also on exposure duration. Currently available animal studies may suggest differing mechanisms (depending on the duration of exposure) by which living organisms react to NP contact. Nevertheless, due to considerable inconsistencies in the recent literature and the lack of standardised test methods - a reliable hazard assessment of NMs is still limited. Therefore, international organisations (e.g. NIOSH) suggest utmost caution when potential exposure of humans to NMs occurs, as long as evidence of their toxicological and genotoxic effect(s) is limited.