DNA damage in leukocytes of workers occupationally exposed to 1-bromopropane

1-bromopropane (1-BP; n-propyl bromide) (CAS No. 106-94-5) is an alternative to ozone-depleting chlorofluorocarbons that has a variety of potential applications as a degreasing agent for metals and electronics, and as a solvent vehicle for spray adhesives. Its isomer, 2-brompropane (2-BP; isopropyl bromide) (CAS No. 75-26-3) impairs antioxidant cellular defenses, enhances lipid peroxidation, and causes DNA damage in vitro. The present study had two aims. The first was to assess DNA damage in human leukocytes exposed in vitro to 1- or 2-BP. DNA damage was also assessed in peripheral leukocytes from workers with occupational exposure to 1-BP. In the latter assessment, start-of- and end-of-work week blood and urine samples were collected from 41 and 22 workers at two facilities where 1-BP was used as a solvent for spray adhesives in foam cushion fabrication. Exposure to 1-BP was assessed from personal-breathing zone samples collected for 1-3 days up to 8h per day for calculation of 8h time weighted average (TWA) 1-BP concentrations. Bromide (Br) was measured in blood and urine as a biomarker of exposure. Overall, 1-BP TWA concentrations ranged from 0.2 to 271 parts per million (ppm) at facility A, and from 4 to 27 ppm at facility B. The highest exposures were to workers classified as sprayers. 1-BP TWA concentrations were statistically significantly correlated with blood and urine Br concentrations. The comet assay was used to estimate DNA damage. In vitro, 1- or 2-BP induced a statistically significant increase in DNA damage at 1mM. In 1-BP exposed workers, start-of- and end-of-workweek comet endpoints were stratified based on job classification. There were no significant differences in DNA damage in leukocytes between workers classified as sprayers (high 1-BP exposure) and those classified as non-sprayers (low 1-BP exposure). At the facility with the high exposures, comparison of end-of-week values with start-of-week values using paired analysis revealed non-sprayers had significantly increased comet tail moments, and sprayers had significantly increased comet tail moment dispersion coefficients. A multivariate analysis included combining the data sets from both facilities, log transformation of 1-BP exposure indices, and the use of multiple linear regression models for each combination of DNA damage and exposure indices including exposure quartiles. The covariates were gender, age, smoking status, facility, and glutathione S-transferase M1 and T1 (GSTM1, GSTT1) polymorphisms. In the regression models, start-of-week comet tail moment in leukocytes was significantly associated with serum Br quartiles. End-of-week comet tail moment was significantly associated with 1-BP TWA quartiles, and serum Br quartiles. Gender, facility, and GSTM1 had a significant effect in one or more models. Additional associations were not identified from assessment of dispersion coefficients. In vitro and in vivo results provide limited evidence that 1-BP exposure may pose a small risk for increasing DNA damage.     

Health risk assessment of occupational exposure to styrene depending on the type of industry: Data from the Workplace Environmental Monitoring Program in Korea

Data from the Workplace Environmental Monitoring Program was used to evaluate the concentrations and risk of occupational exposure to styrene in different industries to identify which industries should be prioritized for styrene exposure management. Risk assessments were conducted for the five industries with several workplaces that mostly use styrene: motor vehicle and motorcycle maintenance and repair services, other chemical product manufacturing, ship and boat building, basic chemical manufacturing, and plastic products manufacturing. The highest central tendency exposure was found in the plastic products manufacturing industry (10.14 mg/m³). In addition, the hazard quotient (HQ) for central tendency exposure exceeded 1 only in the plastic products manufacturing industry. Almost two-thirds (62.2%) of workplaces in the plastic products manufacturing industry have an HQ exceeding 1. We conclude that workers in the plastic products manufacturing industry are at the highest risk for styrene exposure, and those in motor vehicle and motorcycle maintenance and repair service and basic chemical manufacturing are at the lowest risk. These results show that styrene exposure could be most effectively managed by prioritizing control measures in the plastic products manufacturing industry.     

Cancer and Non-Cancer Risk Assessment from Exposure to Arsenic,Copper, and Cadmium in Borehole,Tap, and Surface Water in the Obuasi Municipality,Ghana

Cancer and non-cancer risk assessment from exposure to As, Cd, and Cu by resident adults and children from different water sources in Obuasi Municipality, Ghana, were measured in this study in accordance with the U.S. Environmental Protection Agency's (USEPA's) Human Health Risk Assessment guidelines. The results of cancer health risk for resident adults in Obuasi exposed to As in their tap water for both Central Tendency Exposure (CTE) and Reasonable Maximum Exposure (RME) parameters, respectively, are 6.6 × 10^?4 and 5.5 × 10^?6. For resident children in Odumasi, we obtained 4.7 × 10^?1 (CTE) and 6.7 × 10^?1 (RME). The results of the study obtained in most cases were found to exceed the USEPA's acceptable cancer risk range of 1 × 10^?6 to 1 × 10^?4 (i.e., 1 case of cancer out of 1,000,000 people to 1 case of cancer out of 10,000 people). Similarly, the results of the non-cancer human health risk for both resident adults and children were also found in most cases to be greater than the USEPA's acceptable non-cancer human health hazard index of 1.     

Risk assessment of workers exposed to crystalline silica aerosols

This study was conducted to determine the concentration of airborne respirable crystalline silica (ARCS) particles and to evaluate its risk level among workers employed in eight different workplaces in Iran. They included sandblasting operations, ceramic production, sand and gravel work, brick production, asphalt manufacturing, foundry operation, glass making, and stone cutting. Personal exposure to ARCS was measured in randomly selected samples from each workplace. The maximum and minimum average of ARCS concentration in the eight workplaces were observed in foundry operation (0.338 ± 0.110 mg/m³) and glass manufacturing (0.125 ± 0.093 mg/m³), respectively. The average concentration of ARCS in all assessed working conditions were higher than the permitted limit of occupational contact recommended by Technical Committee of the Iranian Ministry of Health, treatment and medical education (0.025 mg/m³). Overall, the results showed a serious lack of control in Iranian industries with respect to workers' exposures to ARCS.     

Biological monitoring of occupational exposure to 1-bromopropane by means of urinalysis for 1-bromopropane and bromide ion

The purposes of the present study are (1) to develop a sensitive analytical method to measure 1-bromopropane (1-BP) in urine, (2) to examine if 1-BP or bromide ion (Br) in urine is a useful biomarker of exposure to 1-BP, and (3) to identify the lowest 1-BP exposure concentration the method thus established can biomonitor. A factory survey was carried out on Friday, and 33 workers (all men) in cleaning and painting workshops participated; each worker was equipped with a diffusive sampler (carbon cloth KF-1500 as an adsorbent) to monitor 1-BP vapour for an 8-h shift, and offered a urine sample at the end of the shift for measurement of 1-BP and Br in urine. In addition, 10 non-exposed men offered urine samples as controls. The performance of the carbon cloth diffusive sampler was examined to confirm that the sampler is suitable for monitoring time-weighted average 1-BP vapour exposure. A head-space GC technique was employed for analysis of 1-BP in urine, whereas Br in urine was analysed by ECD-GC after derivatization to methyl bromide. The workers were exposed to vapours of seven other solvents (i.e. toluene, xylenes, ethylbenzene, acetone, etc.) in addition to 1-BP vapour; the 1-BP vapour concentration was 1.4 ppm as GM and 28 ppm as the maximum. Multiple regression analysis however showed that 1-BP was the only variable that influenced urinary 1-BP significantly. There was a close correlation between 1-BP in urine and 1-BP in air; the correlation coefficient (r) was >0.9 with a narrow variation range, and the regression line passed very close to the origin so that 2 ppm 1-BP exposure can be readily biomonitored. The correlation of Br in urine with 1-BP in air was also significant, but the r (about 0.7) was smaller than that for 1-BP, and the background Br level was also substantial (about 8 mg l^-1). Thus, it was concluded that 1-BP in end-of-shift urine is a reliable biomarker of occupational exposure to 1-BP vapour, and that Br in urine is less reliable.     

Biodegradation of 4-bromophenol by Arthrobacter chlorophenolicus A6 in batch shake flasks and in a continuously operated packed bed reactor

The present study investigated growth and biodegradation of 4-bromophenol (4-BP) by Arthrobacter chlorophenolicus A6 in batch shake flasks as well as in a continuously operated packed bed reactor (PBR). Batch growth kinetics of A. chlorophenolicus A6 in presence of 4-BP followed substrate inhibition kinetics with the estimated biokinetic parameters value of μ _max = 0.246 h^?1, K _i = 111 mg L^?1, K _s  = 30.77 mg L^?1 and K = 100 mg L^?1. In addition, variations in the observed and theoretical biomass yield coefficient and maintenance energy of the culture were investigated at different initial 4-BP concentration. Results indicates that the toxicity tolerance and the biomass yield of A. chlorophenolicus A6 towards 4-BP was found to be poor as the organism utilized the substrate mainly for its metabolic maintenance energy. Further, 4-BP biodegradation performance by the microorganism was evaluated in a continuously operated PBR by varying the influent concentration and hydraulic retention time in the ranges 400–1,200 mg L^?1 and 24–7.5 h, respectively. Complete removal of 4-BP was achieved in the PBR up to a loading rate of 2,276 mg L^?1 day^?1.     

Respiratory symptoms and ventilatory function defects among Para rubber wood sawmill workers in the south of Thailand

The aim of this study was to assess the associations between respiratory symptoms and pulmonary defects of Para rubber sawmill workers in the South of Thailand. A cross-sectional study was conducted among 687 workers in Para rubber wood sawmills and a subset of sawmill workers from four factories participated in spirometric measurements and personal dust samplings. Multiple logistic regression analysis was used to explore risk factors pulmonary impairment. The exposed workers had higher respirable wood dust exposure (0.902 mg/m³) compared with the unexposed groups (0.185 mg/m³). The exposed group had significantly higher prevalence than the unexposed group for chest tightness (odds ratio (OR) = 2.79) and shortness of breath (OR = 2.27). The ventilatory function values (FEV1 and FVC) were lower for the exposed group compared with the unexposed group (2.41 vs 2.55 L/s and 2.91 vs 3.01 L/s, respectively). The results suggest that sawmill factories using Para rubber tree wood should implement appropriate exposure control measures to reduce wood dust exposure to protect their employees.     

Risks of hormonally active pharmaceuticals to amphibians: a growing concern regarding progestagens

Most amphibians breed in water, including the terrestrial species, and may therefore be exposed to water-borne pharmaceuticals during critical phases of the reproductive cycle, i.e. sex differentiation and gamete maturation. The objectives of this paper were to (i) review available literature regarding adverse effects of hormonally active pharmaceuticals on amphibians, with special reference to environmentally relevant exposure levels and (ii) expand the knowledge on toxicity of progestagens in amphibians by determining effects of norethindrone (NET) and progesterone (P) exposure to 0, 1, 10 or 100 ng l⁻¹ (nominal) on oogenesis in the test species Xenopus tropicalis. Very little information was found on toxicity of environmentally relevant concentrations of pharmaceuticals on amphibians. Research has shown that environmental concentrations (1.8 ng l⁻¹) of the pharmaceutical oestrogen ethinylestradiol (EE₂) cause developmental reproductive toxicity involving impaired spermatogenesis in frogs. Recently, it was found that the progestagen levonorgestrel (LNG) inhibited oogenesis in frogs by interrupting the formation of vitellogenic oocytes at an environmentally relevant concentration (1.3 ng l⁻¹). Results from the present study revealed that 1 ng NET l⁻¹ and 10 ng P l⁻¹ caused reduced proportions of vitellogenic oocytes and increased proportions of previtellogenic oocytes compared with the controls, thereby indicating inhibited vitellogenesis. Hence, the available literature shows that the oestrogen EE₂ and the progestagens LNG, NET and P impair reproductive functions in amphibians at environmentally relevant exposure concentrations. The progestagens are of particular concern given their prevalence, the range of compounds and that several of them (LNG, NET and P) share the same target (oogenesis) at environmental exposure concentrations, indicating a risk for adverse effects on fertility in exposed wild amphibians.     

Development of a headspace gas chromatographic test for the quantification of 1- and 2-bromopropane in human urine

A test procedure was developed for the detection and quantification of 1- and 2-bromopropane in human urine. 1-Bromopropane (1-BP) is a commonly used industrial solvent, and 2-bromopropane (2-BP) is often found as an impurity component in industrial grade 1-BP. Both compounds are a health concern for exposed workers due to their chronic toxicity. Bromopropanes have been associated with neurological disorders in both animals and humans. Sample preparation consisted of diluting urine with water and fortification with 1-bromobutane (1-BB), which was used as an internal standard; then each sample was sealed in a headspace vial. A static-headspace sampler (Teledyne-Tekmar Model 7000) was used to heat each sample at 75 degrees C for a 35-min equilibrium time. Quantification was by means of a gas chromatograph (GC) equipped with an electron capture detector (ECD) and a dimethylpolysiloxane (DB-1) capillary column. A recovery study using fortified urine samples at multiple concentrations (0.5-8 microg/ml) demonstrated full recovery; 104-121% recovery was obtained. Precision ranged from 5 to 17% for the 15-20 spiked samples used at each concentration, which were analyzed over multiple experimental trial days. The limit of detection (LOD) for this test procedure was approximately 2 ng/ml 1-BP and 7 ng/ml 2-BP in urine. A recovery study of 1- and 2-BP from fortified urine stored in vials appropriate for field collection was also completed. These results and other factors of the development and validation of this test procedure will be discussed.     

Development of an HPLC–MS procedure for the quantification of N-acetyl-S-(n-propyl)-l-cysteine,the major urinary metabolite of 1-bromopropane in human urine

An analytical procedure was developed for the detection and quantification of N-acetyl-S-(n-propyl)-l-cysteine (n-propylmercapturic acid, AcPrCys), a metabolite and biomarker for exposure to 1-bromopropane (1-BP). 1-BP is used as an industrial solvent and exposure is a health concern for industrial workers due to its toxicity. It has been associated with neurological disorders in both animals and humans. Urine sample preparation for the determination of AcPrCys consisted of solid phase extraction (SPE). Urine samples on preconditioned SPE (C18) columns were washed with 40% methanol/60% water solution prior to elution with acetone. Quantification was by means of a liquid chromatograph (LC) equipped with a mass spectrometer (MS) using an Aqua 3 μm C18 300A column and [d₇]-AcPrCys was used as internal standard. Electrospray ionization (ESI) was used with the MS operated in the negative ion mode and selected ion monitoring (SIM) at m/z 204 for AcPrCys and m/z 211 for [d₇]-AcPrCys. Demonstrated recovery of urine samples fortified at multiple levels (0.625–10 μg/ml) varied between 96 and 103% of theory with relative standard deviations (RSD) of 6.4% or less. The limit of detection (LOD) for the procedure was approximately 0.01 μg/ml AcPrCys in urine. These data will be discussed as well as other factors of the development of this test procedure.     

Development of a gas chromatographic test for the quantification of the biomarker 3-bromopropionic acid in human urine

An accurate and precise method was developed for the detection and quantification of 3-bromopropionic acid (3-BPA), a metabolite and biomarker for exposure to 1-bromopropane (1-BP). 1-BP is used as an industrial solvent and exposure is a health concern for industrial workers due to its toxicity. It has been associated with neurological disorders in both animals and humans. Urine sample preparation for the determination of 3-BPA consisted of liquid-liquid extraction (LLE) with ethyl acetate and silylation with N-methyl-N-[tert-butyldimethylsilyl]trifluoroacetamide (MTBSTFA). Quantification was by means of a gas chromatograph (GC) equipped with a mass selective detector (MSD) using a dimethylpolysiloxane (HP-1) capillary column and 3-chloropropionic acid was used as an internal standard in the procedure. Demonstrated accuracy and precision during this method's validation was good; recovery varied between 93 and 98% with relative standard deviations (R.D.S.) of 5.7% or less. The limit of detection (LOD) for the procedure was approximately 0.01microg/ml 3-BPA in urine. These data and other factors of the development and validation of this test method will be discussed.     

Rare earth elements (REEs) in PM10 and associated health risk from the polymetallic mining region of Nandan County,China

A total of 26 samples were collected from Dachang, Chehe and Liuzhai in Nandan County, China, in order to investigate the concentrations of rare earth elements (REEs) and associated health risk in particulate matter. The concentrations of REEs in Dachang (23.54 ng/m³), Chehe (20.29 ng/m³) were significantly higher than those in Liuzhai (8.1 ng/m³). The light rare earth elements (LREEs) account for 87.08%, 87.09%, and 86.17% of the total REE burden in PM10 at Dachang, Chehe, and Liuzhai, respectively, indicating that the distribution pattern of REEs in PM10 was characterized by the obvious fractionation of LREEs. Enrichment factor calculation indicated that EFs for La, Ce, Nd, Pr, and Nd in PM10 from Dachang and Chehe were greater than 2, indicating moderate enrichment. Source identification indicated that REEs in PM10 from Dacheng and Chehe originated from anthropogenic activities such as mining and smelting activities, while REEs in PM10 from Liuzhai were associated with natural sources, like soil erosion. Noncarcinogenic and carcinogenic risks associated with the exposure of REEs in PM10 were negligible based on the health risk assessment models. However, greater noncarcinogenic risk for children was found in studied areas compared with the adults.     

Occupational exposures and reproductive health: 2003 Teratology Society Meeting Symposium summary

Assuring reproductive health in the workplace challenges researchers, occupational safety and health practitioners, and clinicians. Most chemicals in the workplace have not been evaluated for reproductive toxicity. Although occupational exposure limits are established to protect 'nearly all' workers, there is little research that characterizes reproductive hazards. For researchers, improvements in epidemiologic design and exposure assessment methods are needed to conduct adequate reproductive studies. Occupational safety and health programs' qualitative and quantitative evaluations of the workplace for reproductive hazards may differ from standardized approaches used for other occupational hazards in that estimates of exposure intensity must be considered in the context of the time-dependent windows of reproductive susceptibility. Clinicians and counselors should place the risk estimate into context by emphasizing the limitations of the available knowledge and the qualitative nature of the exposure estimates, as well as what is known about other non-occupational risk factors for adverse outcomes. This will allow informed decision-making about the need for added protections or alternative duty assignment when a hazard cannot be eliminated. These policies should preserve a worker's income, benefits, and seniority. Applying hazard control technologies and hazard communication training can minimize a worker's risk. Chemical reproductive hazard training is required for workers by the Occupational Safety and Health Administration's Hazard Communication Standard. The National Institute for Occupational Safety and Health (NIOSH) has formed a National Occupational Research Agenda Team to promote communication and partnering among reproductive toxicologists, clinicians and epidemiologists, to improve reproductive hazard exposure assessment and management, and to encourage needed research.     

Inhalable dust,endotoxins and (1–3)-β-<Emphasis Type="SmallCaps">d</Emphasis>-glucans as indicators of exposure in waste sorting plant environment

The aim of the study was to assess the levels of inhalable dust, endotoxins and (1–3)-β-d-glucans as agents harmful to the respiratory tract of workers of municipal waste sorting plants and interaction between these agents based on the measurements taken in two plants with different processing capacities. The study was conducted in summer season in two waste sorting plants (WSPs) differing in processing capacity. Samples of bioaerosol for inhalable dust (gravimetric method), endotoxins (LAL test in kinetic, chromogenic version) and (1–3)-β-d-glucans (Glucatell test in kinetic version) were collected from 42 sorting workers using individual aspirators with glass fiber filters during the work shift. Average geometric concentrations (geometric standard deviation; min–max) of inhalable dust, endotoxins and (1–3)-β-d-glucans were: WSP1: 1.7 mg m^?3 (2.2; 0.6–6.9 mg m^?3); 15.9 ng m^?3 (2.1; 5.4–78.9 ng m^?3), 55.1 ng m^?3 (1.8; 20.7–188.6 ng m^?3) and WSP2: 0.8 mg m^?3 (2.2; 0.2–3.8 mg m^?3), 9.8 ng m^?3 (2.4; 1.6–29.7 ng m^?3), 45.0 ng m^?3 (3.2, 5.7–212.9 ng m^?3), respectively. A significantly higher concentration of inhalable dust was recorded in WSP1 with bigger processing capacity compared to WSP2 (less processing capacity). Significant (p < 0.05) and very high correlations (Spearman rank R > 0.7) were found between the concentrations of all analyzed harmful agents. Processing capacity of waste sorting plants differentially affects the concentrations of inhalable dust, whereas concentrations of endotoxins and glucans are less clearly affected. This suggests that relative concentrations of endotoxin and glucan are depending on the waste sorting capacity.     

Acute toxicity of ammonia and nitrite to different ages of Pacific cod (Gadus macrocephalus) larvae

Abstract

This study was conducted to evaluate the acute toxicity of ammonia and nitrite to three developmental stages of Pacific cod (Gadus macrocephalus) larvae (11, 22, and 35 days after hatching, with mean total lengths of 4.63 ± 0.14, 5.83 ± 0.17, and 7.46 ± 0.23 mm, respectively). The results showed for the first time that the acute toxicity of ammonia and nitrite is closely related to the age of Pacific cod larvae, and the acute toxicity of ammonia or nitrite increased with increased Pacific cod larval growth. Lethal concentrations (LC₅₀) of un-ionized ammonia nitrogen (UIAN) for a 48-h exposure in 11-day post-hatch, 22-day post-hatch, and 35-day post-hatch Pacific cod larvae were 1.72, 0.69, and 0.32 mg L^?1, respectively. The 48-h LC₅₀ of nitrite nitrogen to Pacific cod larvae 11-day post-hatch, 22-day post-hatch, and 35-day post-hatch were 831.76, 269.15, and 223.87 mg L^?1, respectively. The present findings demonstrate that the acute toxicity of ammonia for Pacific cod larvae is much higher than that of nitrite.     

Reproductive and developmental toxicity of formaldehyde: a systematic review

Formaldehyde, the recently classified carcinogen and ubiquitous environmental contaminant, has long been suspected of causing adverse reproductive and developmental effects, but previous reviews were inconclusive, due in part, to limitations in the design of many of the human population studies. In the current review, we systematically evaluated evidence of an association between formaldehyde exposure and adverse reproductive and developmental effects, in human populations and in vivo animal studies, in the peer-reviewed literature. The mostly retrospective human studies provided evidence of an association of maternal exposure with adverse reproductive and developmental effects. Further assessment of this association by meta-analysis revealed an increased risk of spontaneous abortion (1.76, 95% CI 1.20-2.59, p=0.002) and of all adverse pregnancy outcomes combined (1.54, 95% CI 1.27-1.88, p<0.001), in formaldehyde-exposed women, although differential recall, selection bias, or confounding cannot be ruled out. Evaluation of the animal studies including all routes of exposure, doses and dosing regimens studied, suggested positive associations between formaldehyde exposure and reproductive toxicity, mostly in males. Potential mechanisms underlying formaldehyde-induced reproductive and developmental toxicities, including chromosome and DNA damage (genotoxicity), oxidative stress, altered level and/or function of enzymes, hormones and proteins, apoptosis, toxicogenomic and epigenomic effects (such as DNA methylation), were identified. To clarify these associations, well-designed molecular epidemiologic studies, that include quantitative exposure assessment and diminish confounding factors, should examine both reproductive and developmental outcomes associated with exposure in males and females. Together with mechanistic and animal studies, this will allow us to better understand the systemic effect of formaldehyde exposure.     

Quantitative health impact of indoor radon in France

Radon is the second leading cause of lung cancer after smoking. Since the previous quantitative risk assessment of indoor radon conducted in France, input data have changed such as, estimates of indoor radon concentrations, lung cancer rates and the prevalence of tobacco consumption. The aim of this work was to update the risk assessment of lung cancer mortality attributable to indoor radon in France using recent risk models and data, improving the consideration of smoking, and providing results at a fine geographical scale. The data used were population data (2012), vital statistics on death from lung cancer (2008–2012), domestic radon exposure from a recent database that combines measurement results of indoor radon concentration and the geogenic radon potential map for France (2015), and smoking prevalence (2010). The risk model used was derived from a European epidemiological study, considering that lung cancer risk increased by 16% per 100 becquerels per cubic meter (Bq/m³) indoor radon concentration. The estimated number of lung cancer deaths attributable to indoor radon exposure is about 3000 (1000; 5000), which corresponds to about 10% of all lung cancer deaths each year in France. About 33% of lung cancer deaths attributable to radon are due to exposure levels above 100 Bq/m³. Considering the combined effect of tobacco and radon, the study shows that 75% of estimated radon-attributable lung cancer deaths occur among current smokers, 20% among ex-smokers and 5% among never-smokers. It is concluded that the results of this study, which are based on precise estimates of indoor radon concentrations at finest geographical scale, can serve as a basis for defining French policy against radon risk.     

The effect of benthic sediments on dissolved nutrient concentrations and fluxes

The Ria Formosa is a meso-tidal coastal lagoon experiencing enhanced nutrient concentrations. Assessment of sediment–seawater interaction is essential if nutrient dynamics and the risk of eutrophication are to be fully understood. Pore water concentrations of dissolved inorganic and organic phosphorus, ammonium, nitrate and nitrite were determined in cores from six sites. Changes in nutrients concentrations were measured in intertidal pools on sand and mud between tides. Dissolved inorganic phosphorus (DIP) concentrations (~200 μmol l⁻¹) and effluxes (123 ± 14 μmol m⁻² h⁻¹) were greater from sand than mud (37 ± 10 μmol m⁻² h⁻¹), possibly due to the binding of P with the <63 μm fraction. NH₄⁺ effluxes were high outside the Anc?o Basin (821 ± 106 μmol m⁻² h⁻¹) and were associated with Enteromorpha sp. mats. The greatest NO₃⁻ efflux was from sediments near a salt marsh (170 ± 67 μmol m⁻² h⁻¹). These sediment fluxes of P were not sufficient to account for elevated P concentrations seen by other workers on the ebb tide from the Anc?o Basin. Intertidal pools were sinks for Dissolved Inorganic Nitrogen (DIN) and DIP over the 6 h exposure period. Thus, tidepools may be an important route of nutrients into sediments that enhances the effects of sediments on seawater nutrient concentrations.     

Interactions of radiofrequency radiation-induced hyperthermia and 2-methoxyethanol teratogenicity in rats

Radiofrequency (RF) radiation is used in a variety of workplaces. In addition to RF radiation, many workers are concurrently exposed to numerous chemicals; exposed workers include those involved with the microelectronics industry, plastic sealers, and electrosurgical units. The developmental toxicity of RF radiation is associated with the degree and duration of hyperthermia induced by the exposure. Previous animal research indicates that hyperthermia induced by an elevation in ambient temperature can potentiate the toxicity and teratogenicity of some chemical agents. We previously demonstrated that combined exposure to RF radiation (10 MHz) and the industrial solvent, 2-methoxyethanol (2ME), produces enhanced teratogenicity in rats. The purpose of the present research is to determine the effects of varying the degree and duration of hyperthermia induced by RF radiation (sufficient to maintain colonic temperatures at control [38.5], 39.0, 40.0, or 41.0 °C for up to 6 h) and 2ME (100 mg/kg) administered on gestation day 13 of rats. Focusing on characterizing the dose-response pattern of interactions, this research seeks to determine the lowest interactive effect level. Day 20 fetuses were examined for external and skeletal malformations. The results are consistent with previous observations. Significant interactions were observed between 2ME and RF radiation sufficient to maintain colonic temperatures at 41 °C for 1 h, but no consistent interactions were seen at lower temperatures even with longer durations. These data indicate that combined exposure effects should be considered when developing both RF radiation and chemical exposure guidelines and intervention strategies. Bioelectromagnetics 18:349–359, 1997. © 1997 Wiley-Liss, Inc.     

A Dietary Assessment of Selenium Risk to Aquatic Birds on a Coal Mine Affected Stream in Alberta,Canada

Selenium is a trace element of concern in the McLeod River basin downstream from two recently-closed coal mines in west-central Alberta, Canada. Aquatic birds breed on streams in the area and may be exposed to excessive amounts of selenium through their diets. In this article, we present the results of a dietary-based assessment of the risk that selenium may pose to two aquatic bird species, the American Dipper (Cinclus mexicanus) and the Harlequin Duck (Histrionicus histrionicus), on one of the coal mine–affected streams, the Gregg River. The study consisted of (1) a literature-based toxicity assessment, (2) simulation of selenium exposure in the diets and eggs of the two species, and (3) a risk assessment that coupled information on toxicity and exposure. Diet and egg selenium concentrations associated with a 20% hatch failure rate were 6.4 and 17 μ g · g^?1 dry wt, respectively. Simulated dietary selenium concentrations were about 2.0–2.5 μ g · g^?1 higher on the Gregg River than on reference streams for both species. Simulated predicted egg concentrations averaged 2.0 and 1.4 μ g · g^?1 higher on the Gregg River than on reference streams for American Dippers and Harlequin Ducks, respectively. When simulated dietary concentrations were considered, hatch failure rates on the Gregg River were predicted to average 12% higher in American Dippers and 8% higher in Harlequin Ducks than at reference streams. Corresponding values were only 3% for both species when predicted egg concentrations were used. Elevated levels of selenium in insects in some of the reference streams were unexpected and raised a question as to whether aquatic birds have evolved a higher tolerance level for dietary selenium in these areas.