Dioxins are known to be a class of highly toxic and persistent environmental contaminants. Among them the toxicity of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) has been the most intensively studied, and it has been classified as a human carcinogenic substance by the International Agency for Research on Cancer (IARC). Although the mechanism of carcinogenesis by TCDD is unclear, it is now considered to have act a cancer promoter. In this review, we discuss the ability of TCDD to induce oxidative stress in vivo, the mechanism of the oxidative stress induction, and how oxidative stress relates to the development of cancer. We then discuss the advantages of measuring the level of oxidative stress in people exposed to dioxins in epidemiological studies for cancer risk assessment. We also discuss several methods of measuring the level of oxidative stress in humans.
Several epidemiological studies have shown that the prevalence of ischemic heart disease is higher in occupational drivers than in people with other occupations. Although occupation categories can be surrogate measures for coronary risk factors, the relationships between taxi driving and severity of coronary heart disease (CHD) has not been investigated. Even more important, the contribution of risk factors to the severity of CHD in taxi drivers remains unclear. Our study tested the hypothesis that taxi driving could be associated with the severity of CHD. We also examined the relation between this occupation and risk factors and social lifestyle. We analyzed the coronary angiograms of 57 consecutive male taxi driver patients and compared them with those of 215 ageadjusted male non-taxi-driver patients. The number of diseased vessels and risk factors were compared between two groups. The prevalence of myocardial infarction and multi-vessel disease was higher in the taxi-driver patients than in the non-taxi-driver patients. The taxi-driver patients had higher prevalence of body mass index (BMI), diabetes, and smoking, higher levels of low-density lipoprotein cholesterol (LDL-C), and lower levels of apolipoprotein AI (ApoAI). Multiple logistic regression analysis showed that multi-vessel disease was associated with BMI and diabetes mellitus in taxi-driver patients. The taxi-driver patients were characterized by more extensive coronary atherosclerosis associated with higher prevalence of diabetes mellitus and obesity. These characteristics may be explained by in part their working environment.
CO2 arc welding in a confined space was simulated in a laboratory by manipulating a welding robot which worked in a small chamber to experimentally evaluate the welder's exposure to welding fumes, ozone and carbon monoxide (CO). The effects of the welding arc on the air temperature rise and oxygen (O2) concentration in the chamber were also investigated. The measuring points for these items were located in the presumed breathing zone of a welder in a confined space. The time averaged concentrations of welding fumes, ozone and CO during the arcing time were 83.55 mg/m3, 0.203 ppm and 0.006%, respectively, at a welding current of 120A-200A. These results suggest serious exposure of a welder who operates in a confined space. Air temperature in the chamber rose remarkably due to the arc heat and the increase in the welding current. No clear decrease in the O2 concentration in the chamber was recognized during this welding operation. A model of air duct ventilation was constructed in the small chamber to investigate the strategy of effective ventilation for hazardous welding contaminants in a confined space. With this model we examined ventilation efficiency with a flow rate of 1.08-1.80 m3/min (ventilation rate for 0.40-0.67 air exchanges per minute) in the chamber, and proved that the exposure level was not drastically reduced during arcing time by this air duct ventilation, but the residual contaminants were rapidly exhausted after the welding operation.
This paper concerns the influence of air temperature and of the direction of drafts on subjective and physiological responses. In three experimental series 58 healthy persons (50 men, 8 women, 20-29 yrs) were exposed to drafts in overall 446 experimental sessions. Drafts were applied either horizontally or vertically with mean air velocities of 0.1 to 0.3 m/s and a turbulence intensity of 50%. Air temperature was varied between 11 and 23°C and metabolic rates between <70 and 156 Ws and skin temperature was measured at the forearm and at the neck. Subjective and physiological responses were systematically related to air temperature. Draft-induced general annoyance, draft-induced local annoyance (neck, forearm) and the drop of the corresponding skin temperature were inversely related to air temperature. Concerning the direction horizontal drafts seem to cause somewhat stronger reactions. The predictive model developed by Toftum1) underestimates the percentage of persons annoyed. A modified version increases the predictive power significantly2).
This study was conducted to assess various environmental exposure measurements (total dust, ammonia and endotoxin) of poultry workers at the province of Isfahan, Iran. The results show that the workers who worked in enclosed systems of parent stock barns have the highest exposure to total and respirable dust: 21.3 ± 3.2 and 4.6 ± 0.9 mg/m3, respectively. In comparison with different ages of chicken, the highest concentration of total and respirable dust were 5.4 ± 0.7 and 3.3 ± 0.7 mg/m3 in the 45th day. In the above mentioned situation, the results of endotoxin concentrations were 20.6 ± 1.1, 23.6 ± 2.2, 21.3 ± 1.2 and 26.8 ± 1.8 ng/m3, respectively. Ammonia concentrations had the highest rate in enclosed systems of laying hens in winter and the 45th day of chicken age, measuring 33.2 ± 5.2 and 20.2 ± 3.0 mg/m3, respectively.
Recently there has been an increasing incidence of occupational cervicobrachial disorders (OCD) and writer's cramp in office workers using ballpoint pens in writing operations. For the sake of workers who use ballpoint pens, it is essential to prevent such health hazards. It has been observed that a strong gripping pressure on the ballpoint pen significantly contributes to the development of these conditions. The present authors have been developing a new ballpoint pen by altering the grip area in such a way as to reduce the gripping pressure, and thus prevent OCD. The purpose of this study is to compare our ballpoint pen (new pen) with a conventional ballpoint pen (conventional pen) for the load that they exert on the upper limb during one hour of continuous writing. Electromyograms (EMG) and upper limb pain scores are used as indicators. The conventional pen used was selected from commercially available ballpoint pens widely used in offices. The grip area is cylindrical with an 8.3 mm diameter. It is manufactured of hard plastic, which can make it feel rigid and slippery to the user. The new pen has a cylindrical grip area that flares out at the bottom, near the pen-tip, and has a diameter ranging from 11.9-13.6 mm. In addition, the grip is constructed of a 2 to 3 mm-thick silicon rubber sleeve that is softer and less slippery in comparison with the conventional pen. Twelve students (5 males and 7 females) without any preexisting cervicobrachial disorders were asked to transcribe an English text for one hour, alternately using the two kinds of pens. The EMG of the flexor pollicis brevis was measured and recorded every second, while subjective pain scores were recorded every five minutes for the thumb, forefinger, middle finger, thenar, forearm extensor (forearm) and shoulder. The EMG of the flexor pollicis brevis and the pain scores for the thumb, forefinger, middle finger, forearm and shoulder were significantly lower for the new pen than for the conventional pen. These results suggest that after an hour of continuous writing, the new pen reduces the muscle load on the upper limb, and therefore mitigates fatigue in this area.
Lead exposure of workers in a Japanese copper smelter was assessed by determining lead levels in blood, air and flue cinder at the copper smelting processes. All the samples were analyzed for lead by atomic absorption spectrometry. Mean lead levels of air were highest at the anode department followed by the converter, smelter and blend departments. The mean level of blood lead of the workers in the anode department was also the highest among the four smelting departments. The mean blood lead levels of the workers in each department were positively correlated with their air lead levels (r=0.99, p<0.01). This study indicates therefore that workers in copper smelters have been exposed to lead in their workplace. Though this finding has already been reported in preceding studies, the Ordinance on Prevention of Lead Poisoning in Japan has not included copper smelter into its target job categories if their lead concentration in the raw material is less than 3%. The limitation of the present Ordinance which defines the targets by the types of job and not by the actual exposure, is discussed.
In order to clarify poor sleep habits and prevalence in sleep problems (disturbances) of healthy male white-collar workers and the relationship of these to age and job type, a total of 1, 161 Japanese employees of an electric equipment manufacturing company (aged 23 to 59, mean 37 years) were surveyed by means of a mailed questionnaire. The workers were asked about eleven sleep habits. They were also divided into four groups according to age and job type: 23-29 (n=226), 30-39 (n=597), 40-49 (n=225) and 50-59 (n=113); managerial (n=209), professional (n=336), technical (n=475) and clerical (n=134). In this study, the sleep problems were defined as who had at least one of the following four poor sleep habits: 1) taking more than 30 minutes to fall asleep, 2) awakening during sleep (ADS) almost every day, 3) early morning awakening (EMA) almost every day, and 4) excessive daytime sleepiness (EDS) at work almost every day. Analyses showed that sleep problems were present in 26.0% of workers; the problems were most serious among workers aged 50 years and more (36.0%) which may be due to a significant increase in the prevalence rate of EMA. The results revealed that sleep problems are common in male white-collar daytime workers. The findings also suggest a need for increased attention to sleep problems in older workers and younger ones with EDS at work.
Concentrations of fumes, ozone (O3), carbon monoxide (CO), nitric oxide (NO), manganese (Mn) and total and hexavalent chromium (Cr) as well as size distribution of fumes were measured at a point corresponding to the welder's breathing zone during CO2-arc welding, using a welding robot and three kinds of wires. Concentrations of fumes, O3, CO, Mn and total-Cr were found to exceed their corresponding occupational exposure limit (OEL) values, while the concentrations of NO and Cr(VI) were below those OEL levels. Airborne concentration of Mn exceeded its OEL value, and the Mn content was 8 times higher in welding fumes than in the wire. Using an additive equation of OEL and exposure concentration of each hazardous component, health risk in welders with combined exposure to welding fumes and gases was assessed as 18.6 to 46.0 times of OEL, which exceeded the unity. This finding suggests that effective protection of welders from the exposure can be attained by use of the supplied-air respirator or combined use of a dust respirator and a local exhaust system.
To examine how repeated cooling of fingers with a rest pause schedule at work affects cold-induced vasodilatation (CIVD), pain and cold sensation in fingers, six healthy men aged 21 to 23 years immersed their left index fingers six times in stirred water at 10°C for 10 minutes. After each cold-water immersion of the fingers, 5-minute rest pause was taken to observe the recovery process of the indicators. This cold-water immersion/rest pause test was carried out in a range of three ambient temperature conditions: 30°C (warm), 25°C (thermoneutral), and 20°C (cool) as experienced in daily life. At the ambient temperatures of 30°C and 25°C, marked CIVD response occurred and the CIVD reactivity did not significantly change upon repetition of cold-water immersion. The lowered finger skin temperature also tended to recover quickly to the pre-immersion level during each post-immersion rest period. At the ambient temperature of 20°C, however, the CIVD response weakened continuously upon repetition of immersion and almost disappeared during the final immersion. The recovery of finger skin temperature during each post-immersion rest was gradually delayed upon repetition of immersion. At every ambient temperature, finger pain and cold sensation induced by each cold-water immersion significantly decreased upon repetition of immersion and completely disappeared during each post-immersion rest period. Oral temperature during the experiment showed no significant change at the ambient temperatures of 25°C and 30°C, but it decreased significantly at the ambient temperature of 20°C. These results suggest that in a cool work environment where the body core temperature is liable to decrease, repeated finger cooling may weaken CIVD reactivity and delay the recovery of finger temperature during post-immersion rest periods. In such lower ambient temperature work conditions, subjective judgements such as the decrease in finger pain and cold sensation during repeated finger cooling and the absence of them during post-immersion rest may not be reliable indicators for monitoring the risk of progressive tissue cooling and frostbite formation.
Metallothioneins (MTs) are small metal-binding proteins that have a role in the defense against heavy metals. Mammalian MT genes are transcriptionally activated by metals such as Cd and Zn through multiple copies of the metal responsive element (MRE) present in the 5'-flanking region. To examine whether each MRE in a single promoter has a distinct role, we characterized seven MREs located upstream of the human MT-IIA gene. By transient transfection experiments using MRE-driven reporter gene constructs, individual MREs were assayed for the activity to mediate transcription in response to several heavy metal species. Four MREs including MREs a, b, e and g independently mediated reporter gene expression in response to Zn, Cd and Hg, while other MREs were not responsive to any of these metals. These results suggest that the multiplicity of MRE contributes to enhancing its activity, rather than providing functional diversity.
Solid-liquid extraction separation based on a speciation method was studied for selective determination of vanadium(IV) and vanadium (V). Both V (IV) and V (V) cations transform to oxoacid anion along with pH changes in the solution. The pH values for the transition points are different from each other and the difference was utilized in the separation. In the first step, particulate samples are dissolved by strong acids such as 1 M H2SO4 or 85% H3PO4. The pH of the strong acidic sample solutions of V (IV) and V (IV) are adjusted to the range between 3 and 4. In this condition, V (IV) is in the form of cation but V (V) is anion. The pH adjusted solution is applied to an anion exchange column. The solution is expected to contain V (IV) only. The trapped V (V) anion is eluted as VO2+ cation by a pH 1 acid. The author and coworker have already developed an HPLC separation method utilizing this separation concept. However, the HPLC method has some limitations, mainly originated in physical and chemical weaknesses of the HPLC column. In the present study, a firm solid-liquid column is adopted to replace the feeble HPLC column as a separation device. And a simple and convenient pH adjustment technique for making the sample solution is investigated at the same time. With these improvements, the speciation method developed with strong acidic solutions could determine the amount of V (IV) and V (V) in various environmental and biological samples.
The relationship between blood lead (PbB) level and urinary delta-aminolevulinic acid (ALAU) level was examined in a total of 3, 636 lead-exposed workers in a periodic medical examination in 1992, in accordance with the Ordinance on Prevention of Lead Poisoning. The results were consistent with previously reported results2, 4) in that ALAU level was found to increase with an increase in PbB level above 22.4 μg/dl (1.35 as a logarithmic value) and to rise markedly above 35.5 μg/dl (1.55). On the contrary, the geometric means of ALAU levels appeared to decrease with an increase in PbB levels within a range between a logarithmic value of 0.15 (1.4 μg/dl) and 1.25 (17.8 μg/dl). Because the earliest sign of the adverse health effects of lead is reported to occur at a PbB level of 20 μg/dl, the relationship between PbB level and ALAU level was examined at PbB levels below 20 μg/dl. A regression formula was obtained, Y (log ALAU (mg/l)) = 0.0570X (log PbB (μg/dl)) + 0.4099. This result indicates that ALAU level decreases with a concomitant increase in PbB level lower than 20 μg/dl.
The association of coffee consumption with the development of increased serum aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) activities over 4 years was studied in 1221 liver dysfunction-free (serum AST and ALT ?39 IU/l and no medical care for or no past history of liver disease) Japanese male office workers aged 35 to 56 years. From the analysis using the Kaplan-Meier method, the estimated incidence of serum AST and/or ALT ?40 IU/l, ?50 IU/l, and ?60 IU/l decreased with an increase in coffee consumption. From the Cox proportional hazards model, coffee drinking was independently inversely associated with the development of serum AST and/or ALT ?40 IU/l (p=0.019 by test for tendency), ?50 IU/l (p=0.002), and ?60 IU/l (p=0.007), controlling for age, body mass index, alcohol intake, and cigarette smoking. These results suggest that coffee may be protectively against the liver dysfunction in middle-aged Japanese men.