Exposure to electromagnetic fields in the magnetic resonance imaging environment in South Africa

Occupational exposure to radiofrequency (RF) and static magnetic fields at magnetic resonance imaging (MRI) suites is of continuing concern to personnel who routinely work in this environment. Questions regarding the levels of occupational RF and static field exposure have increased with the increasing demand for anesthetics to be administered in this environment. The present study was thus designed towards addressing the above-mentioned problem by gaining information regarding exposure levels of clinical personnel at MRI units in South Africa. Three 1.5 MRI units in Bloemfontein, South Africa were utilized to evaluate the exposure of clinical personnel to the electromagnetic fields present in the MRI environment over a period of time and during different clinical MRI procedures. Three rounds of measurements of RF fields in the MRI environment were done. All the three measurement rounds were focused on the low frequencies, 5 Hz–32 kHz, as well as on the high frequencies, 300 kHz–40 GHz. First round measurements were done to establish the background of the RF fields in and around the magnet room during an MRI examination. Second round RF field measurements were done at a specific location, 1 m away from the bore on the right-hand side of the bed, in the MRI room. The third round measurements were of the same format as the second round, but the specific location was against the magnet bore. Two pieces of Narda Safety Test Solution instruments, the EFA-300 and EMR-300, were used to measure the electromagnetic and magnetic exposure fields generated from the MRI scanners. Results of the measurements indicate that the electromagnetic fields measured during different clinical procedures do not exceed the International Commission on Non-Ionizing Radiation Protection (2000) guidelines in these units. Results from round two and three showed that the RF and gradient exposure 1 m and up against the bore entrance does not exceed these guidelines (rms average over 6 min). Ongoing new developments in MRI scanning create the need for continuously monitoring exposure of patients and workers to the EMF fields in the MRI environment.     

Thallium in the Environment and Health Effects

Thallium is present in the natural environment in low concentration, being found most frequently in the sulphide ores of a number of heavy metals. Atmospheric emission and deposition from industrial sources has resulted in raised levels in the vicinity of mineral smelters, coal burning power plants, brick works and cement plants. In contaminated areas, raised levels are found in vegetables, fruit and in farm animals. Thallium is used industrially in small quantities, with uses in electronics, in the production of certain glasses and crystals and in medical diagnostics. It has in the past been commonly used as a rodenticide, but its use has now been banned in many countries. Thallium salts are now considered to be amongst the most toxic compounds known. With regard to population exposure, an epidemiological study in an area with high thallium concentrations in soil and garden vegetables centred on a cement plant, has found evidence of a dose response relationship between thallium concentration in urine and a number of non-specific subjective symptoms. Much further research is required to investigate the possible adverse health effects of thallium following population exposure.     

Bioconcentration kinetics of PCBs in various parts of the lifecycle of the tadpoles Xenopus laevis

Polychlorinated biphenyls （PCBs） in Xenopus laevis have been reported only for a few congeners. Additionally, there is very little information on the ability of Xenopus laevis to bioconcentrate PCBs. To address these issues, the tadpole Xenopus laevis was exposed to Aroclor 1254 mixtures in water at room temperature for 110 d followed by an additional 110 d of nonspiked PCBs in the water for the control group. During the whole process, bioconcentration factors （BCFs） of PCBs ranged from 1180 to 15670. For most PCB congeners, the highest and lowest bioconcentrations of the kinetic curves were found to be remarkably simultaneous, respectively. All 141 PCB congeners under the same experimental conditions had no linear correlation on the lgBCF versus lgKow relationship. The relationship between lgBCFs and lgKow followed a parabolic pattern indicative of selective bioconcentration, suggesting that the kinetic curves of the PCB congeners observed in the lifecycle of the tadpoles may be concentrated due to the amphibian special species and internal metabolism. In contrast, lgBCFs for PCBs were inversely related to lgKow, suggesting that a metabolism of the higher Kow PCB congeners occurred. These results support the author＇s conclusion that the tadpole Xenopus laevis plays major roles in the bioconcentration of PCB congeners, and demonstrated that the exposure kinetic curves of PCB congeners are complex. Besides the amphibian metamorphous development, the lifecycle of the tadpole Xenopus laevis also may be of importance in determining the bioconcentration of PCB congeners.     

Occupational risk from static magnetic fields of MRI scanners

The health care staff operating magnetic resonance imaging (MRI) scanners are exposed to static magnetic field of significant spatial heterogenity and high level of flux density—usually existing permanently during the shift. The personnel can also be exposed to pulses of magnetic field of high rate of rise/fall, so-called gradient fields, which exist only during examination of patients. The level of workers’ exposure depends both on the type of the magnet and on the ergonomical characteristic of design of the particular MRI scanner. This paper presents the current state of the art on occupational exposure to static magnetic field health effects, gaps in scientific data, MRI workers’ exposure characteristics, research needs, and suggestions for the exposure assessment protocol for future investigations.     

Practical aspects of occupational EMF exposure assessment

Electromagnetic fields exposure assessment methodology is briefly presented. The basic problems defined for the practical use of electromagnetic fields measurements and numerical calculations carried out for workers exposure assessment in real occupational situations are discussed. The examples of data from real workplace are presented, focusing: spatial distribution of electromagnetic fields affecting worker’s body, complex characteristics of the frequency content, workers activities/moving in the workplace, field impedance, etc. The situation when the use of calculations is required is discussed. The basic requirements for workers exposure assessment protocols are presented. The possible range of the use of internal and external measures of exposure level is also discussed.     

Stress-70 as indicator of heavy metals accumulation in blue mussel Mytilus edulis

The induction of stress-70 (Hsp70) in the blue mussels Mytilus edulis from southern Baltic after exposure to cadmium, lead and copper, administrated individually and/or as a mixture, was investigated by means of standard Western blotting using a clone 3A3 monoclonal antibody. The general course of the stress-70 induction was found to be similar for all tested metals. It could be characterised by three main features: (1) The induction of stress-70 proteins was only slightly increased at low metal concentration. (2) Strong induction of stress-70 occurred at high concentration of metals. Combination of metals (Cd+Cu) was found to increase the stress-70 level more intensely than related concentrations of singularly applied metals. (3) Five weeks of long depuration had no effect on stress-70 levels. Experiments revealed different induction of stress-70 as a response to cadmium, lead and copper exposure and confirm that the applied technique might serve as a versatile tool to assess invertebrate stress reaction to environmentally relevant heavy metals.     

Concentrations,Cumulative Exposure and Critical Levels of Ozone in Ireland

Concentrations of tropospheric ozone(O₃) and exceedance of critical levels to vegetationhave been investigated and mapped for Ireland. Hourlyozone concentration data (1995–1997) at 7 sevenmonitoring stations and the CORINE landcover database,supported by a Geographical Information System, wereused. AOT40 (Accumulated exposure Over a Threshold of 40ppb) was calculated for daylight hours for each station,and mapped using surface interpolation. Average O₃concentrations vary from year to year, and were estimatedto be 28 ppb, 26 ppb and 24 ppb for 1995, 1996 and 1997respectively. Ozone concentrations show a large diurnalvariation, with a maximum in the afternoon and a minimumat night-time. The critical level for crops and (semi-)natural vegetation was exceeded in all years examined.The highest exceedance occurred in 1995, where thecritical level was exceeded for almost 35% of the mappedarea. Approximately 15% and 1% of the mapped area wasexposed to exceedance levels during 1996 and 1997respectively. The maximum cumulative exposures (AOT40)were approximately 5000, 3890 and 3230 ppbh in 1995, 1996and 1997 respectively. The critical level for forests wasnot exceeded during the period of investigation.     

Personal carbon monoxide exposures of preschool children in Helsinki, Finland—comparison to ambient air concentrations

The associations of personal carbon monoxide (CO) exposures with ambient air CO concentrations measured at fixed monitoring sites, were studied among 194 children aged 3–6 yr in four downtown and four suburban day-care centers in Helsinki, Finland. Each child carried a personal CO exposure monitor between 1 and 4 times for a time period of between 20 and 24 h. CO concentrations at two fixed monitoring sites were measured simultaneously. The CO concentrations measured at the fixed monitoring sites were usually lower (mean maximum 8-h concentration: 0.9 and 2.6 mg m⁻³) than the personal CO exposure concentrations (mean maximum 8-h concentration: 3.3 mg m⁻³). The fixed site CO concentrations were poor predictors of the personal CO exposure concentrations. However, the correlations between the personal CO exposure and the fixed monitoring site CO concentrations increased (−0.03–−0.12 to 0.13–0.16) with increasing averaging times from 1 to 8 h. Also, the fixed monitoring site CO concentrations explained the mean daily or weekly personal CO exposures of a group of simultaneously measured children better than individual exposure CO concentrations. This study suggests that the short-term CO personal exposure of children cannot be meaningfully assessed using fixed monitoring sites.     

Human geography of New Orleans’ high-lead geochemical setting

Previous soil lead studies in New Orleans focused on the geochemical footprint and its health impacts. This study examines the human geography of race, income, and age in pre-Katrina metropolitan New Orleans within the context of lead accumulation in soils. Sample points of soil lead data (n = 5,467) collected in 1998–2000 were mapped in a geographic information system (GIS), binned into 9 ranges, and queried by (1) 2000 Census racial demographic data, (2) 1999 median household income, and (3) 2000 age data. The absolute population generally declines as lead levels increase except at lead levels from 200–400 to 400–1,000 mg/kg when population increases; the African–American population comprises a disproportionate share of this cohort. The high-lead areas occur in the inner city, home to the largest populations of African-Americans in New Orleans. The mean household income curve indicates that lower economic groups are at risk to higher levels of lead. A total of 44,701 children under the age of 5 years, plus 123,579 children aged 5–17, lived in census block groups containing at least one sample point with over 100 mg/kg lead, and these include 23,124 and 64,064 young people, respectively, who live near at least one point over 400 mg/kg. Lead exposure affects a panoply of outcomes that influence the health and welfare of the community. Unless corrected, children are likely to return to the same or, because of lack of lead-safe practices during renovation, even higher exposure risks than before the flooding of New Orleans.     

基于蒙特卡罗模拟的高校室内甲醛暴露健康风险评价

为了量化分析高校新建教学楼室内环境污染引起的健康风险问题,调查了武汉市某高校新建教学楼室内甲醛污染状况,引入美国环保署(EPA)致癌风险模型,运用蒙特卡罗模拟室内甲醛暴露对不同性别的教师和学生受体造成的健康风险,进行不确定性分析,并研究各参数敏感度。结果表明,该教学楼室内的监测点监测得到的甲醛质量浓度数据中有5%超过标准限值(0.10 mg/m³,参照《室内空气质量标准》),存在一定的健康风险。健康风险评估结果显示,男性的癌症风险和超标率略高于女性,教师群体健康风险平均值超过限值(1×10^-6)9倍左右,且高于学生群体3~4倍。对教师造成影响最大的参数为暴露时间,对学生影响最大的参数为甲醛质量浓度,在无致癌风险的室内甲醛质量浓度和在可接受健康风险限值(1×10^-6)下,推荐教师每日平均暴露时间不超过0.31 h/d(男性)和0.35 h/d(女性)。