High-Throughput Exposure Assessment Tool (HEAT) for exposure-based prioritization of chemicals

Abstract

High-throughput methods are now routinely used to rapidly screen chemicals for potential hazard. However, hazard-based decision-making excludes important exposure considerations resulting in an incomplete estimation of chemical safety. Models to estimate exposure exist, but are generally unsuited to keep up with high-throughput demands. The High-Throughput Exposure Assessment Tool (HEAT) is designed to efficiently predict near-field exposure to consumers and workers via inhalation, oral and dermal routes. HEAT is based on well-known modeling algorithms and provides default model parameters to support reasonably conservative exposure estimates. Underlying chemical-specific data are uploaded or entered by the end user. HEAT’s main strength is the flexible tiered screening functionality, which enables exposure estimates for single or multiple chemicals simultaneously. Hypothetical case examples highlighting the application of HEAT to more complex exposure estimates for alternative and aggregate assessments are provided.     

Space efficient system for small animal, whole body microwave exposure at 1.6 GHz

A space efficient, whole body microwave exposure system for unrestrained laboratory animals utilizing a flared parallel plate waveguide is described. The system comprises an Iridium wireless signal source, signal generator, power supply and amplifier (400 W), a coax to waveguide transition, an open ended, flared parallel plate waveguide, and animal exposure area with a dipole field sensing antenna. Across the waveguide aperture the system provides uniform exposure (+/-3 dB incident RF power density) for small animals (rats, mice or hamsters) in up to 18 standard cages for housing groups of animals. Overall system dimensions are 3.6 m (d)x2.4 m (w)x1.6 m (h). Operating at 1.62 GHz, the system provided average power density of 3.7 W/m(2) in the cage area, resulting in a calculated whole body dose of 0.07 W/kg and a calculated average brain dose of 0.19 W/kg.     

Measurement of the individual exposure to 50 and 16 2/3 Hz magnetic fields within the Bavarian population.

This study investigates the individual magnetic field exposures at 16 2/3 and 50 Hz of 1952 people, selected from the Bavarian population. Personal flux density meters ("Field Watcher FW2A") were worn by the participants for 24 h. Every second, the flux density was recorded for both frequencies and for the three spatial axes (dynamic range per axis: several nT up to 100 microT at 50 Hz, 150 microT at 16 2/3 Hz). For 50 Hz fields, the mean of the 1,952 individual means was 0.101 microT and that of the individual medians was 0.047 microT. High level exposures occurred mainly during working hours. Only 2.4% of the subjects showed individual medians higher than 0.2 microT. About 53% of all volunteers were working on the day of recording. Levels for craftsmen (n = 148; mean individual mean: 0.166 microT) were generally higher than those for office workers (n = 624; mean individual mean: 0.107 microT). Flux densities exceeding 100 microT at 50 Hz were measured in 31 persons. The total time with such extreme exposures amounts to nearly 21 min, less than 0.001% of the total time for all measurements (5.3 years). To our knowledge, this is the first exposure study where 16 2/3 Hz magnetic fields (caused by electrified railways) have additionally been monitored over 24 h. For persons living next to railway lines, the mean individual mean (0.156 microT) and mean individual median (0.102 microT) were calculated. Over all, the mean exposures are only 0.1% of the magnetic flux density limit for 50 Hz (100 microT) and about 0.05% of the limit (300 microT) for 16 2/3 Hz recommended by the International Commission on Non-Ionizing Radiation Protection.     

Better data needed from pregnancy registries

This article is a consensus position statement from the Research Committee of the Organization of Teratology Information Specialists (OTIS). The Committee believes that more specific information on the timing and dose of drug exposures from pregnancy birth defect registries sponsored by pharmaceutical companies (herein called pregnancy registries) would improve the estimation of risk for developmental toxicity (i.e., growth alteration, structural anomalies, functional/neurobehavioral deficits, or death). Specifically, the Committee believes that the exposure timing should be stated in gestational weeks and days rather than simply weeks. In addition, the Committee believes that the exposure dose should be stated in patient‐specific terms, such as body weight (mg/kg) or body surface area (mg/m²) rather than simply dose strength. Although the focus of this position is pregnancy registries, it also is applicable to any source of medication‐induced embryo‐fetal toxicity. Birth Defects Research (Part A), 2009. © 2008 Wiley‐Liss, Inc.     

RF personal exposimetry on employees of elementary schools, kindergartens and day nurseries as a proxy for child exposures

Personal RF exposimetry has been in the focus of the bioelectromagnetics community in the last few years. With a few exceptions, exposimetry studies focused on adults, because measuring the exposure of children, one of the most important target groups, introduces many complications.The main feature of our study is to select teachers and kindergarten caretakers as volunteers. They are expected to receive similar exposure patterns as the children because they spend the workday close to them. Thus they can stand as proxies for estimation of exposures of children.Volunteers belonging to one of two groups (elementary school teachers, n = 31; employees of kindergartens and day nurseries, n = 50) in Hungarian cities received a Personal Exposimeter (PEM) for 24 h each. Only workdays, when the volunteers worked near children, were considered. 51 additional volunteers (office workers) were measured as controls.The volunteers wore the PEMs on their bodies. Those activities marked in the exposure diaries as work were further classified into 5 categories based on the level of certainty that they actually worked near children during that activity. Subsets of the full dataset were derived and compared based on this categorization.It was found that relaxation of the selection criteria often under- or overestimates exposure. The differences of estimation depend on the frequency band and sub-population: the kindergarten and teacher groups differ in this regard. For most frequency bands the majority of data points was below the detection limit. Derived child exposures are comparable to the worktime exposure of adults (control group).     

Survey of residential 50 Hz EMF exposure from transformer stations

In Hungary it is typical that 10/04 kV transformer stations are being installed in multistory residential and office buildings. Magnetic fields (MFs) up to several tens of microT have been measured in apartments close to transformers. The aim of the present study was to provide systematic assessment of MF exposure of residents living above transformer stations. Out of 41 addresses provided by the electricity supplier, current load of 21 transformers and MF in 21 apartments was measured. Spot MFs at 1 m height and time weighted average 24 h MF exposure at bed height was measured. All-day personal MF exposure was measured at waist and HOME exposure was calculated. BED exposure was measured at bed height. Participants kept a time-activity diary. The time-weighted average 24 h MF exposure (3.03 microT) exceeded the usual residential exposure (<0.2 microT). The mean HOME and BED personal exposure above transformers was 0.825 and 1.033 microT, respectively. Our study provides exposure assessment of a cohort with a wider exposure range, compared to power-line epidemiological studies.     

Spatial and temporal RF electromagnetic field exposure of children and adults in indoor micro environments in Belgium and Greece

Personal radio frequency electromagnetic field (RF-EMF) exposure, or exposimetry, is gaining importance in the bioelectromagnetics community but only limited data on personal exposure is available in indoor areas, namely schools, crèches, homes, and offices. Most studies are focused on adult exposure, whereas indoor microenvironments, where children are exposed, are usually not considered. A method to assess spatial and temporal indoor exposure of children and adults is proposed without involving the subjects themselves. Moreover, maximal possible daily exposure is estimated by combining instantaneous spatial and temporal exposure. In Belgium and Greece, the exposure is measured at 153 positions spread over 55 indoor microenvironments with spectral equipment. In addition, personal exposimeters (measuring EMFs of people during their daily activities) captured the temporal exposure variations during several days up to one week at 98 positions. The data were analyzed using the robust regression on order statistics (ROS) method to account for data below the detection limit. All instantaneous and maximal exposures satisfied international exposure limits and were of the same order of magnitude in Greece and Belgium. Mobile telecommunications and radio broadcasting (FM) were most present. In Belgium, digital cordless phone (DECT) exposure was present for at least 75% in the indoor microenvironments except for schools. Temporal variations of the exposure were mainly due to variations of mobile telecommunication signals. The exposure was higher during daytime than at night due to the increased voice and data traffic on the networks. Total exposure varied the most in Belgian crèches (39.3%) and Greek homes (58.2%).     

Evaluation of RF electromagnetic field exposure levels from cellular base stations in Korea

This article presents the measurement results of human exposure to CDMA800 and CDMA1800 signals at locations in Korea where the general public has expressed concern. Measurements were performed at 50 locations across the country to compare the electromagnetic field levels with the general public exposure compliance limits. At each site, the distances between the nearest single or co‐located base station and measurement positions were within a range of approximately 32–422 m. The measured exposure levels were very low compared with the international standard and the Korean human protection notice. The highest field level was 1.5 V/m, which corresponds to 0.15% of the International Commission on Non‐Ionizing Radiation Protection (ICNIRP) guidelines for human exposure. Bioelectromagnetics 31:495–498, 2010. © 2010 Wiley‐Liss, Inc.     

Exposure of children to residential magnetic fields in Norway: Is proximity to power lines an adequate predictor of exposure?

The aim of this work was to study the exposure to magnetic fields of children living at different distances from a power line and to evaluate how well theoretical calculations compared with actual exposure. Personal exposure instruments were carried for 24 h by 65 schoolchildren living 28–325 m from a 300 kV transmission line; the current load was 200–700 A. About half of the children attended a school far from the power line, whereas the other half attended a school located about 25 m from the line. Exposure to magnetic fields was analyzed for three categories of location: at home, at school, and at all other places. Time spent in bed was analyzed separately. The results indicated that children who lived close to a power line had a higher magnetic field exposure than other children. The power line was the most important source of exposure when the magnetic field due to the line was greater than about 0.2 μT. Exposure at school influenced the 24 h time-weighted average results considerably in those cases where the distance between home and power line was very different from the distance between school and power line. The calculated magnetic field, based on line configuration, current load, and distance between home and power line, corresponded reasonably well with the measured field. However, the correlation depends on whether home only or 24 h exposure is used in the analysis and on which school the children attended. The calculated magnetic field seems to be a reasonably good predictor of actual exposure and could be used in epidemiological studies, at least in Norway, where the electrical system normally results in less ground current than in most other countries. Bioelectromagnetics 18:47–57, 1997. © 1997 Wiley-Liss, Inc.     

Millimeter wave power density in aqueous biological samples

Power density distribution inside a water sample placed between two parallel lossy dielectric plates (Polystyrene) was calculated using Fresnel equations for the frequency range of 42.25-53.57 GHz. Due to the multiple internal reflections from the sample boundaries, the distribution of the power density within the thin sample is more uniform than that within a semi-infinite medium. The power density in a sample depends on the thicknesses of the sample and the adjacent dielectric plates. For the given frequency range the sample thickness optimal for power density uniformity varies between 0.28 and 0.33 mm. The front plate has a significant effect on the magnitude of the power density within the sample but little effect on the power density distribution. The thicker the rear plate, the greater is the non uniformity of the power density distribution within the sample. Based on the calculated data, we determined the dimension of an exposure chamber providing the optimal power density distribution uniformity for mm-wave irradiation.     

Adult onset acute myelogenous leukemia and electromagnetic fields in Los Angeles County: bed-heating and occupational exposures

In a large matched population-based case-control study of acute myelogenous leukemia (AML), we did not find incident AML in Los Angeles County (1987-1994) to be associated with previous exposure to electric blankets, electrically heated waterbeds, or occupations with presumed high exposure to electromagnetic fields.     

Adult Dermal Sediment Loads Following Clam Digging in Tide Flats

Sediment contamination is common and assessment of potential dermal exposure to sediments is of interest to risk assessors. However, few measurements of coastal sediment (as opposed to terrestrial soil) adherence to skin have been reported in the literature. Results are reported here for sediment loads on the skin of 18 adults engaged in clam digging for periods of up to 90 minutes in a tide flat in Rhode Island. Post-activity geometric mean loads were 0.02, 0.12, 0.16, 0.58 and 0.88 mg/cm² on faces, forearms, lower legs, feet and hands, respectively. Pre-activity loadings were less than 0.01 mg/cm² on all body parts except feet. These results are similar to very limited previously reported data obtained from four persons gathering reeds for basketry in a tide flat in Washington State.     

Dietary exposure of Finnish children to heavy metal mixture – a cumulative assessment

A preliminary assessment of the cumulative exposure to heavy metals among Finnish preschool children is reported. Cadmium, lead, arsenic,and mercury affect many of the same organs in the human body. The effects are mostly caused by oxidative stress or disruption of enzyme function. The cumulative effects of the heavy metals on the central nervous system and on the kidneys are determined based on national concentration and consumption data, and comparison of the relative toxicity of the heavy metals is based on dose–response values found in the literature. The cumulative effects were assumed to be additive. The main contributors to kidney toxicity among the studied population groups were cadmium and lead, while lead was the main contributor to neurotoxic effects.     

Exposure risks to pesticide applicators posed by the use of electric backpack sprayers and stretcher-mounted sprayers in orchards

Abstract

The introduction of the pesticide registration system in pesticide risk assessments has promoted the scientific and safe use of pesticides, and the assessment of occupational exposure risk. In the present study, we performed an experiment in a citrus orchard subject to normal orchard management practices. By measuring the exposure of applicators’ (farmers and technicians) body parts to 45% malathion emulsifiable concentrate during its application using electric backpack sprayers (0.25?KPa) and stretcher-mounted sprayers (1.5?KPa), the unit exposure (UE) was determined. The risks of exposure for pesticide applicators who adopted five different protective measures (A: no personal protective equipment (PPE), i.e., no clothes, no gloves, no caps, and no socks; B: short-sleeved top and shorts; C: short-sleeved top, shorts, and a single pair of gloves; D: short-sleeved top, shorts, a single pair of gloves, and a cap; E: long-sleeved top, long pants, a single pair of gloves, and a cap) were also assessed. The results were as follows: 1) The total levels of exposure for pesticide applicators using electric backpack sprayers and stretcher-mounted sprayers were 3613.63?µg and 5654.28?µg, respectively. When electric backpack sprayers were used, the body parts that had the highest exposure were the head (13.8%), hands (19.9%) and back (14.0%), and when stretcher-mounted sprayers were used, the hands (32.5%) and lower legs (21.1%) had the highest level of exposure; 2) In the absence of PPE, the UE values for farmers who used electric backpack sprayers and farmers who used stretcher-mounted sprayers were significantly different. However, when PPE was used, the difference in UE values between the farmers using the two different types of sprayers was not significant; 3) When protective measure A was adopted, the risk quotient (RQ) values of the farmers and technicians who used electric backpack sprayers for the application of malathion were 1.44 and 0.54, respectively; the corresponding RQ values when protective measure B was adopted were 0.97 and 0.28, respectively. When stretcher-mounted sprayers were used for the application of chlorpyrifos, the RQ value of the farmers who adopted protective measure E was 0.43 while other types of PPE use resulted in RQ values greater than 1. In contrast, the RQ value for technicians was 1.62 when protective measure A was used and 1.02 when protective measure B was adopted, whereas other types of PPE use resulted in RQ values less than 1. Therefore, besides increasing the awareness of personal protection among pesticide applicators, improvement in the management of pesticide use and the enhancement of standard operations are of practical significance for controlling occupational exposure to pesticides.     

The pattern of exposure to static magnetic field of nurses involved in activities related to contrast administration into patients diagnosed in 1.5 T MRI scanners

Static magnetic fields (SMFs) and time-varying electromagnetic fields exposure is necessary to obtain the diagnostic information regarding the structure of patient's tissues, by the use of magnetic resonance imaging (MRI) scanners. A diagnostic procedure may also include the administration of pharmaceuticals called contrast, which are to be applied to a patient during the examination. The nurses involved in administering contrast into a patient during the pause in examination are approaching permanently active magnets of MRI scanners and are exposed to SMF. There were performed measurements of spatial distribution of SMF in the vicinity of MRI magnets and parameters of personal exposure of nurses (i.e. individual exposimetric profiles of variability in time of SMF affecting the nurse who is performing tasks in the vicinity of magnet, characterized by statistical parameters of recorded magnetic flux density affecting the nurse). The SMF exposure in the vicinity of various MRI magnets depends on both magnetic flux density of the main field B ₀ (applicable to a patient) and the construction of the scanner, but the most important factor determining the workers' exposure is the work practice. In the course of a patient's routine examination in scanners of B ₀ = 1.5 T, the nurses are present over ～0.4–2.9 min in SMF exceeding 0.03% of B ₀ (i.e. 0.5 mT), but only sometimes they are present in SMF exceeding 5% of B ₀ (i.e. 75 mT). When patients need more attention because of their health status/condition, the nurses' exposure may be significantly longer – it may even exceed 10 min and 30% of B ₀ (i.e. 500 mT). We have found that the level of exposure of nurses to SMF may vary from < 5% of the main field (a median value: 0.5–1.5%; inter-quartile range: 0.04–8.8%; max value: 1.3–12% of B ₀) when a patient is moved from the magnets bore before contrast administration, up to the main field level (B ₀) when a patient stays in the magnets bore and nurse is crawling into the bore.     

Extremely low-frequency magnetic fields of transformers and possible biological and health effects

Physiological processes in organisms can be influenced by extremely low-frequency (ELF) electromagnetic energy. Biological effect studies have great importance; as well as measurement studies since they provide information on the real exposure situations. In this study, the leakage magnetic fields around a transformer were measured in an apartment building in Küçükçekmece, Istanbul, and the measurement results were evaluated with respect to the international exposure standards. The transformer station was on the bottom floor of a three-floor building. It was found that people living and working in the building were exposed to ELF magnetic fields higher than the threshold magnetic field value of the International Agency for Research on Cancer (IARC). Many people living in this building reported health complaints such as immunological problems of their children. There were child-workers working in the textile factories located in the building. Safe distances or areas for these people should be recommended. Protective measures could be implemented to minimize these exposures. Further residential exposure studies are needed to demonstrate the exposure levels of ELF magnetic fields. Precautions should, therefore, be taken either to reduce leakage or minimize the exposed fields. Shielding techniques should be used to minimize the leakage magnetic fields in such cases.     

Relative contribution of residential and occupational magnetic field exposure over twenty-four hours among people living close to and far from a power line

This study sought to estimate the relative contribution of exposure to 50 Hz magnetic fields experienced at home, at work/school, or elsewhere to the total exposure over 24 hr. Personal exposure meters were carried by 97 adults and children in the Stockholm area. About half of the subjects lived close (<50 m) to a transmission line and half far (>100 m) away. Spot measurements and calculations for the residential exposure were also made. For subjects living<50 m from the line, the exposure at home contributed about 80% of the total magnetic field exposure, measured in mT-hours. Adults living far away experienced only 38% of the total exposure at home, but children still received 55%. Subjects with low time-weighted average (TWA) exposure both at home and at work spent 84% of their time in fields <0.1 microT, and those with high TWA at both locations spent 69% of their time in fields > or = 0.2 microT. This contrast was diluted if only exposure at one location was considered. For spot measurements and calculations of the residential exposure, both sensitivity and specificity was good. However, the intermediate field exposure category (0.1-0.19 microT) showed poor correlation to the 24 hr personal measurements.