Mercury and lead: Assessing the toxic effects on growth and metal accumulation by Lemna minor

Lemna minor L. was used to investigate the toxic effects of Pb and Hg either alone or in various binary mixtures under the static test conditions. A full-strength Jacob culture medium was used for the long-term cultivation of duckweeds and the experiments. Tests were run for 4 and 7 days. The EC₅₀ values for Pb was estimated as 6.8±0.2 mg L⁻¹ and 5.5±0.1 mg L⁻¹ for a 4 and a 7-day test periods, respectively. Hg was much more toxic than Pb with the EC₅₀ of 0.64±0.03 mg L⁻¹ (4 days) and 0.48±0.02 mg L⁻¹ (7 days). The amounts of Pb uptake by the plants were determined by atomic absorption spectrometer (AAS). The cold vapor AAS-technique (CV-AAS) was used for Hg determination. The interactive effect between Pb and Hg on growth was evaluated as additive on the basis of statistical data analysis. However, an antagonistic interaction was observed on the metal accumulation efficiency.     

Interactive toxic effects of heavy metals and humic acids on Vibrio fischeri

The effect of humic acids (HAs) on the toxicity of copper, zinc, and lead was investigated using the photobacterium Vibrio fischeri (Microtox test) as a test organism. The effects of HAs on metal toxicity were evaluated as functions of time and concentration in pure compound solutions. The toxicities of copper and lead were generally comparable, while the toxicity of zinc was lower than those of the other two metals. The toxicity of copper decreased with the addition of HAs, while the toxicity of zinc remained almost constant. On the other hand, the toxicity of lead increased, depending on the concentration of HAs. The interactive effects between copper and zinc and between lead and zinc were synergistic, while the interactive effect between copper and lead on the bioluminescence of V. fischeri was additive. The presence of HAs caused relatively high toxicity reduction in the binary mixtures of zinc and copper or zinc and lead, while the toxicity reduction in the case of the binary mixture of copper and lead was negligible.     

Neurobehavioural effects of repeated occupational exposure to toluene and paint solvents

In studies of two workforces 44 men exposed to paint solvents and 52 men working with toluene were compared with age matched comparison groups of non-exposed workers. Scores on a series of performance tests were examined, the solvent exposed in each study functioning less well than their comparison group. The apparent deficit among the paint exposed workers was substantial, but this was reduced after allowance for estimated intellectual capacity. No deficit was apparent on rematching with a second comparison group of more appropriate measured capacity. No evidence was found of impaired nerve conduction in the ulnar or median nerves, and few clinical signs of neurological damage were apparent. Nevertheless, in an associated inquiry of neuropsychological symptoms among 236 painters and 128 non-exposed workers a highly significant excess of symptoms was found among those exposed to paint solvents.     

Medicinal herbs: a potential source of toxic metal exposure for man and animals in India

To explore the possibility of translocation of heavy metals into humans and animals, the authors studied 28 commonly used medicinal plants and estimated their heavy metal content. The plant materials were collected from the same sources used by traditional healers and commercial drug manufacturers. The plants were identified, authenticated, and processed for the analysis of toxic metals. Lead and cadmium levels were estimated in leaf, stem bark, root, or seeds, depending on the medicinal value of the plant portion. The authors used an atomic absorption spectrophotometer to determine levels of metals. The mean lead concentration in medical herbs ranged between 2.624 ppm (standard deviation = 0.426) and 32.757 (standard deviation = 0.124 ppm), and the cadmium concentration ranged between 0.056 ppm (standard deviation = 0.002) and 0.419 ppm (standard deviation = 0.006). Interestingly, the heavy metal concentrations (i.e., lead and cadmium) were higher in leaf than in stem bark or roots, and the lowest values were recorded in seeds. No published reports on the permissible level of toxic metals in commonly used medicinal plants of India have come to the authors' attention; therefore, it was difficult for the authors to determine the role of toxic metals in drug-induced health hazards. However, the presence of toxic metals in different plants led to the conclusion that prolonged consumption of such medicinal plants may be detrimental to health.     

Neurobehavioural effects of repeated occupational exposure to toluene and paint solvents.

In studies of two workforces 44 men exposed to paint solvents and 52 men working with toluene were compared with age matched comparison groups of non-exposed workers. Scores on a series of performance tests were examined, the solvent exposed in each study functioning less well than their comparison group. The apparent deficit among the paint exposed workers was substantial, but this was reduced after allowance for estimated intellectual capacity. No deficit was apparent on rematching with a second comparison group of more appropriate measured capacity. No evidence was found of impaired nerve conduction in the ulnar or median nerves, and few clinical signs of neurological damage were apparent. Nevertheless, in an associated inquiry of neuropsychological symptoms among 236 painters and 128 non-exposed workers a highly significant excess of symptoms was found among those exposed to paint solvents.     

Stimulus satiation: effects of repeated exposure to foods on pleasantness and intake

Frequent and repeated exposure to foods produces stimulus satiation or monotony. To explore further the nature of stimulus satiation, two experiments were conducted. Experiment 1 investigated the influence of initial pleasantness and frequency of intake on monotony. Tests showed that bread and butter was eaten more frequently but was liked less than chocolate. Therefore, normal-weight, healthy males were randomly assigned to either a chocolate condition (CC, N=13) or bread and butter condition (BC, N=16). All subjects received fixed amounts of the assigned food (67g/1473kJ of chocolate or 95g/1355kJ of bread and butter) every day for 22 days. On days 1, 8, 15 and 22 subjects consumed this food ad libitum. Pleasantness of taste and desire to eat chocolate declined significantly over time but no such changes were observed for bread and butter. Experiment 2 examined intake, pleasantness and desire to eat chocolate in 53 subjects over a 15 day period, with 3 conditions: control (CS: N=15), fixed (FS: N=20) and variable (VS: N=18). CS received no chocolate except on test days (days 1, 8 and 15), FS received 67g/1473kJ of chocolate daily and VS received increasing amounts of chocolate from 57g/1251kJ on day 1 to 86g/1888kJ by day 12. Pleasantness and desire to eat chocolate declined over time with this being more pronounced for F and V subjects. However, ad libitum intake increased over time. Both experiments demonstrated significant changes in pleasantness and desire to eat chocolate, but no commensurate decline in intake. Thus, although stimulus satiation occurred for subjective ratings of pleasantness and desire to eat chocolate, intake remained unaffected. This apparent dissociation between pleasantness and intake may reflect different processes underlying liking and wanting.     

Microcystin accumulation and antioxidant responses in the freshwater clam Diplodon chilensis patagonicus upon subchronic exposure to toxic Microcystis aeruginosa

We investigated the accumulation and toxicity of microcystin-LR (MCLR) in the digestive gland of the freshwater clam Diplodon chilensis patagonicus. Treated clams were fed with a toxic strain of Microcystis aeruginosa (NPJB1) during 6 weeks and control clams received the non-toxic strain NPDC1. Filtration rate was estimated for both groups. Toxic effects were evaluated through the hepatosomatic index (HSI) and different oxidative stress biomarkers, lipid peroxidation (content of thiobarbituric reactive substances-TBARS), protein oxidation (carbonyl groups) and reduced glutathione (GSH) levels, and enzymatic activities of superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST). The extractable MCLR measured by ELISA in digestive gland extracts showed little or no change during the first 3 weeks and increased significantly at weeks 5 and 6. HSI was reduced by 30% in treated clams at weeks 5 and 6. No significant oxidative damage to lipids or proteins was. All the antioxidant defense parameters analyzed were significantly increased at week 5 or 6. GSH increased in treated clams at week 5, reaching 62% increase at week 6. SOD, CAT and GST activities were significantly increased in treated clams by 50%, 66% and 60%, respectively, at the end of the experiment. D. chilensis patagonicus can be exposed to prolonged cyanobacterial blooms accumulating significant quantities of MCLR, which could be a risk for mammals and birds, which feed on this species and, in a lesser extent, to humans.     

BHT亚急性毒性及致肺巨噬细胞凋亡作用

目的研究2，6-二叔丁基对甲酚（BHT）对大鼠亚急性毒性及其对肺巨噬细胞凋亡作用。方法SD大鼠40只，随机分为BHT高、中、低剂量组（300，600，1200mg／kg）、吐温-80溶剂对照和蒸馏水对照组，每天灌胃，连续8d。处死动物，行肺灌流，用荧光染色及彗星试验检测巨噬细胞凋亡；测脏器系数、一般指标和病理检查。结果染毒第4d，动物体重开始下降，以高剂量组下降为显著．第8d，动物体重有增加的趋势，仍低于正常组，高剂量染毒组大鼠体重依然明显低于中低剂量组。肺和肝脏器系数随染毒剂量增加而增高。病理检查，中、高剂量组大鼠肺泡间隔增厚，炎细胞浸润、无纤维化。肝脏中央静脉周围细胞有点状坏死，以高剂量更明显，并出现假小叶和肝纤维化。血生化显示肝功能异常，且随剂量增加，损伤加重。细胞凋亡检测显示，中、高剂量的BHT具促进肺巨噬细胞凋亡的作用。结论亚急性BHT大剂量染毒可造成大鼠肺、肝等脏器功能性和器质性损伤，BHT可诱发肺巨噬细胞凋亡的产生。     

Environmental exposure to silver and its health effects

Silver (Ag) possesses a well-known antibacterial activity and has been used for medical treatment and cosmetics such as wound dressing and deodorant powders. Occupational Safety and Health Administration (OSHA) and Mine Safety and Health Administration (MSHA) proposed that the permissible exposure limit (PEL) for both metallic and most soluble Ag compounds should be 0.01 mg/m3. Argyria and argyrosis are known to be caused by deposition of insoluble Ag in the dermis and cornea/conjunctiva. However, the metabolic behavior and biological roles of Ag have not been well characterized in mammals. Ag can be absorbed into the systemic circulation from drinking water, and also through parenteral routes such as inhalation and dermal exposure. Experimental studies have demonstrated that Ag+ induces and binds to metallothionein I and II (MTs), which are cysteine-rich proteins, in cells. MTs are major cytoplasmic metal binding proteins and thereby reduce cellular damage caused by toxic heavy metals including Ag. Profiles of Ag distribution in MTs and other Ag-binding proteins can be determined using high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). This technique directly provides information on the intracellular behavior of Ag, which is important for elucidating the mechanism underlying Ag toxicity. Silver nanoparticles (AgNPs) are also commercially used mainly as antimicrobial agents. Despite the widespread use of AgNPs, relatively few studies have been undertaken to evaluate the health effects of AgNP exposure. In the present paper, we discuss the absorption, toxicodynamics, and metabolism of both Ag and AgNPs in mammals and their health effects.     

Experimental exposure to methylformate and its neurobehavioral effects

Objectives: The aim of the study was to investigate the acute effects of experimental methylformate exposure on the nervous system. Methods: In an exposure chamber, 20 subjects were exposed to methylformate at 100 ppm [Swiss maximum allowable concentration (MAC)] for 8 h. The same number of subjects with the same ages (between 20 and 30 years), gender and education level (university) were examined by the same procedure as a control group. The subjects did not know if they were exposed or not. Three times (morning, noon, evening) during these 8 h, mood [Profile of Mood States (POMS)], neurobehavioral performance (reaction, Stroop, nonverbal learning, determination, tracking; Wiener Test System), vision (visual acuity, contrast sensitivity, color sensitivity) and postural sway were tested. During an undemanding test (POMS) and a demanding performance task (determination test), pulse, electromyography (EMG) of the forehead and of the neck were recorded. In the morning and evening spirometry [forced vital capacity (FVC), forced one-second expiration volume (FEV), medium expiration flow (MEF) and peak expiration flow (PEF)] and the odor perception threshold were measured. Results: In the evening, in the exposed group, fatigue was significantly increased and the EMG of the forehead during a demanding task showed a different development during exposure. The other tests showed no significant solvent effect, but 16 of 43 test parameters showed a significant effect of time. Conclusions: The results of this study indicate a possible effect of methylformate exposure on the subjective feeling of fatigue after 8 h exposure at 100 ppm in young and healthy subjects, without measurable impairment of neurobehavioral performance. We assume that a similar effect in normal work, combined with a heavy workload and shift work, can lead to an impairment of productivity, and increase the risk of accidents. Received: 8 February 1998 / Accepted: 22 January 2000     

接触职业有害因素工人精神症状自评量表调查

目的:了解接触职业有害因素工人心理健康状况。方法:采用精神症状自评量表 (SCL-90)对接触职业有害因素工人进行心理健康状况测定。结果:躯体化症状因子平均分高于国 家常模且有显著性差异(P<0.01),其余均低于国家常模(P<0.01或P<0.05)。在不同性别、不同 年龄段阳性症状有差别。结论:职业有害因素对不同年龄段工人心理健康有不同影响。     

Relationship between acetone exposure concentration and health effects in acetate fiber plant workers

In order to clarify the effects of acetone (AC) exposure on health, a cross-sectional study was carried out in 110 male AC-exposed and 67 male nonexposed shift workers. The AC workers ranged in age from 18.7 to 56.8 years (mean: 37.6 years) and in length of AC exposure from 0.5 to 34.3 years (mean: 14.9 years). The nonexposed workers ranged in age from 20.7 to 57.5 years (mean: 41.9 years). AC exposure levels assessed by personal passive monitors and biological monitoring indices measured at the end of the workshift were 19.6–1018 ppm in the breathing zone (AC-E, mean: 364 ppm), 2.5–422 ppm in alveolar air (AC-A, mean: 97.3 ppm) 4–220 mg/1 in blood (AC-B, mean 66.0 ppm), and 0.75–170 mg/l in urine (AC-U, mean: 37.8 mg/1). Symptoms at the end of the workshift with good exposure-response relationships were eye irritation, tearing, and acetone odor, and symptoms within the previous 6 months with good exposure-response relationships were heavy, vague, or faint feeling in the head, nausea, loss of weight, and slow healing of an external wound. In the 30–44 year age range, simple reaction time and digit span scores in a short computerized neuro-behavioral test battery were significantly lower in AC workers, but exposure-response relationships were not clear. Manifest Anxiety Scale scores, Self-rating Depression Scale scores, R-R interval variation on the ECG, hematological examinations, serum biochemistry examinations for liver function, and phagocytic activity of peripheral neutrophils did not show any AC-related differences between the two groups. In view of the reported findings, the current occupational exposure limit of 750 ppm recommended by many governmental and academic associations seems to be too high to prevent the health effects of AC observed in this study.     

Risk indicator of dust exposure and health effects in cement plant workers.

A frequent practical problem of research in developing countries is the lack of reliable records on occupational hazards. To improve this situation, this article suggests and evaluates a two-phase method for estimating particle exposure. The first phase uses the focal group, or homogeneous group, technique to reconstruct the production process and estimate the level of dust exposure. The second phase applies the technique of individual history of exposure to hazards at work, an index that accumulates current and previous exposure. This method was introduced in a Portland cement plant to assess the dust-exposure levels of workers and to evaluate its usefulness in the association between estimated exposure levels and the frequency of health effects--particularly respiratory effects--that occurred as a result of such exposures. The results obtained from the analysis of the production process and of the exposure levels determined by the cement workers showed that it is possible to reconstruct the history of exposure to cement dust during each worker's occupational history. The results also showed that estimated exposure is related to respiratory damage; higher exposure resulted in more serious diseases. This supports the usefulness of the suggested methodology.     

Coal power plant emission exposure and its effect on education access

Aim

We investigate the effects of exposure to coal power plant emissions on school absenteeism for children with asthma, a leading cause of health-related barriers to education.

Subject and methods

We combine responses from the 2007–2009 Behavioral Risk Factor Surveillance System survey with coal power plant emission data to estimate a zero negative binomial regression model of school absences and investigate misspecification bias associated with naive assumptions about emission dispersion and self-selection into treatment groups.

Results

The results show a robust, positive relationship (P?<?0.001) between increases in emission exposure and the likelihood of a school absence due to an asthma episode. Exposure to higher emission volumes is associated with a 1.92–4.81 % higher likelihood of missing an additional school day. Furthermore, assuming uniform emission dispersion and not controlling for self-selection underestimates the effects by 2.72–4.27 times.

Conclusion

Access to education and the ability to develop human capital through schooling are affected for children with respiratory illnesses who are exposed to emissions. Public policies for emission regulation are likely to remain relevant for lowering pediatric respiratory health risks and lowering barriers to educational opportunities.