Increased sensitivity and variability of phytotoxicity responses in Arctic soils to a reference toxicant, boric acid

Industrial and human activities in the Arctic regions may pose a risk to terrestrial Arctic ecosystem functions. One of the most common terrestrial toxicological end points, primary productivity, typically is assessed using a plant phytotoxicity test. Because of cryoturbation, a soil mixing process common in polar regions, we hypothesized that phytotoxicity test results in Arctic soils would be highly variable compared to other terrestrial ecosystems. The variability associated with phytotoxicity tests was evaluated using Environment Canada's standardized plant toxicity test in three cryoturbated soils from Canada's Arctic exposed to a reference toxicant, boric acid. Northern wheatgrass (Elymus lanceolatus) not only was more sensitive to toxicants in Arctic soils, its response to toxicants was more variable compared to that in temperate soils. The phytotoxicity of boric acid in cryosols was much greater than commonly reported in other soils, with a boric acid concentration of less than 150 microg/g soil needed to inhibit root and shoot growth by 20%. Large variability also was found in the phytotoxicity test results, with coefficients of variation for 10 samples ranging from 160 to 79%. The increased toxicity of boric acid in cryosols and variability in test response was not explained by soil properties. Based on our admittedly limited data set of three different Arctic soils, we recommend that more than 30 samples be taken from each control and potentially impacted area to accurately assess contaminant effects at sites in northern Canada. Such intensive sampling will insure that false-negative results for toxicant impacts in Arctic soils are minimized.     

Assessing the toxicity of contaminated soils using the nematode Caenorhabditis elegans as test organism

In this study, nine uncontaminated reference soils and 22 contaminated soils with different physico-chemical properties and contamination patterns were tested with a standardized toxicity test, using the nematode, Caenorhabditis elegans, as test organism. Fertility, growth and reproduction of C. elegans in the soils were compared with the exposure in standard soil Lufa St.2.2. C. elegans showed 100% fertility and a very low variability of growth in the reference soils. Although, reproduction varied considerably between the various reference soils, validity criteria (>30 offspring per test organism) were met in all reference soils. Moreover, Lufa St. 2.2 turned out to be a suitable and representative control soil. In order to clearly classify the effects of the polluted soils on C. elegans, toxicity thresholds were derived for nematode fertility (20% inhibition), growth (10% inhibition) and reproduction (40% inhibition) on the basis of the test inherent variability (MDD=minimal detectable difference), as well as their variability between the uncontaminated reference soils (MTI=maximal tolerable inhibition). The contaminated soils showed clear toxic effects on the nematodes, whereas the toxicity was better correlated to organic than to heavy metal contamination in bulk soil. Interestingly, the results of the nematode toxicity test were not well correlated with those of tests with oligochaetes, collembolans and plants, performed with the same soils, showing that the results are not redundant. The toxicity test using C. elegans turned out to be suitable for testing the toxicity of field collected soils and might by a valuable addition to soil test batteries.     

Ecotoxicity of a polycyclic aromatic hydrocarbon (PAH)-contaminated soil

Soil samples from a former cokery site polluted with polycyclic aromatic hydrocarbons (PAHs) were assessed for their toxicity to terrestrial and aquatic organisms and for their mutagenicity. The total concentration of the 16 PAHs listed as priority pollutants by the US Environmental Protection Agency (US-EPA) was 2634+/-241 mg/kgdw in soil samples. The toxicity of water-extractable pollutants from the contaminated soil samples was evaluated using acute (Vibrio fischeri; Microtox test, Daphnia magna) and chronic (Pseudokirchneriella subcapitata, Ceriodaphnia dubia) bioassays and the EC values were expressed as percentage water extract in the test media (v/v). Algal growth (EC50-3d=2.4+/-0.2% of the water extracts) and reproduction of C. dubia (EC50-7d=4.3+/-0.6%) were the most severely affected, compared to bacterial luminescence (EC50-30 min=12+/-3%) and daphnid viability (EC50-48 h=30+/-3%). The Ames and Mutatox tests indicated mutagenicity of water extracts, while no response was found with the umu test. The toxicity of the soil samples was assessed on the survival and reproduction of earthworms (Eisenia fetida) and collembolae (Folsomia candida), and on the germination and growth of higher plants (Lactuca sativa L.: lettuce and Brassica chinensis J.: Chinese cabbage). The EC50 values were expressed as percentage contaminated soil in ISO soil test medium (weight per weight-w/w) and indicated severe effects on reproduction of the collembola F. candida (EC50-28 d=5.7%) and the earthworm E. fetida (EC50-28 d=18% and EC50-56 d=8%, based on cocoon and juvenile production, respectively). Survival of collembolae was already affected at a low concentration of the contaminated soil (EC50-28 d=11%). The viability of juvenile earthworms was inhibited at much lower concentrations of the cokery soil (EC50-14 d=28%) than the viability of adults (EC50-14 d=74%). Only plant growth was inhibited (EC50-17d=26%) while germination was not. Chemical analyses of water extracts allowed us to identify inorganic water-extractable pollutants as responsible for toxicity on aquatic species, especially copper for effects on D. magna and C. dubia. The soil toxicity on collembolae and earthworms could be explained by 4 PAH congeners-fluorene, phenanthrene, pyrene, and fluoranthene. Yet, toxicity of the cokery soil as a whole was much lower than toxicity that could be deduced from the concentration of each congener in spiked soils, indicating that pollutants in the soil became less bioavailable with ageing.     

Unexpected reduction in reproduction of Collembola exposed to an arsenic-contaminated soil

To assess the problems posed by ecological testing of the toxicity of polluted soils, we applied the Collembola reproduction test to the soil from a mining site polluted by metals. Our aim was to quantify the chronic toxicity of contaminated soil using the Folsomia candida reproduction test. Briefly, the polluted soil, which contains in particular large quantities of arsenic, is mixed in various proportions with a reference soil, and the number of juveniles is counted five weeks later. The results were quite unexpected in that a stronger effect was observed on reproduction with dilute contaminated soil, 0.78 to 3.1%, than with much higher concentrations. The pure contaminated soil is not highly toxic. Arsenic (As) dosage in pore water shows that a change in its bioavailability occurs that may explain the surprising toxicity results. As the main contaminant of the soil was arsenic, we showed that the lowest-observed-effect concentration and the median effective concentration of this metal for the reproduction of F. candida in International Organization for Standardization (Geneva, Switzerland) soil experimentally contaminated with arsenic were low (2.22 and 2.19 microg/g, respectively). Likewise, we showed that pH modifies the bioavailability and the toxicity of As, but we do not think that this parameter explains the test results. These results show that this bioassay should be used cautiously to test toxicity of polluted soils.     

Application of Plant and Earthworm Bioassays to Evaluate Remediation of a Lead-Contaminated Soil

Earthworm acute toxicity, plant seed germination/root elongation (SG/RE) and plant genotoxicity bioassays were employed to evaluate the remediation of a lead-contaminated soil. The remediation involved removal of heavy metals by a soil washing/soil leaching treatment process. A portion of the soil after remediation was rinsed with water in order to simulate exposure to rainfall. The bioassay results showed that the soils before treatment (BT) and after treatment plus water rinsing (RT) were not toxic to earthworms in a 14-day exposure, while after treatment (AT) showed significant toxicity. The LC50 values for Eisenia fetida and Lumbricus terrestris were 44.04 and 28.83 (as % AT soil supplemented in artificial soil), respectively. The phytotoxicity data indicated that all three test soils significantly inhibited lettuce SG/RE in a dose-related manner, with AT being the most phytotoxic. In oats, RT had no effect on SG/RE and AT was more toxic than BT. For the two local site grass seeds tested (blue grama and sideoat grama), the AT soil was the most phytotoxic followed by BT and RT. In Allium cepa (common onion), BT and AT induced similar levels of genetic damage to root tip cells, whereas RT was not genotoxic. High salt levels generated during the remediation process appeared to be responsible for the increased toxicity of AT soil for both plants and earthworms. The rinsing of the AT soil with water effectively removed both acutely toxic and genotoxic components of the soil. Received: 20 May 1996/Revised: 7 August 1996     

Assessing 2,4,6-trinitrotoluene (TNT)-contaminated soil using three different earthworm test methods

Within the scope of a phytoremediation project, the toxicity of 2,4,6-trinitrotoluene (TNT) contaminated soil (and its toxic metabolites) on earthworms was assessed. In addition to the standard acute and reproduction tests (ISO 11268), an avoidance response test was applied. The test methods covered all important ecological relevant endpoints (acute, chronic, behavioral). At a concentration of 1142 mg/kg, TNT caused significant toxic effects in all test methods, but at lower test concentrations no significant acute or reproduction toxic effects could be observed. The avoidance response test, however, showed significant repellent effects at a concentration of 29 mg/kg TNT and therefore proved to be more sensitive than the other tests in this case. Results of the earthworm tests compared well with results of an ecotoxicological biotest battery. Thus, earthworm toxicity tests are useful tools for terrestrial risk assessment but require a hierarchy of test designs that differ in effect levels (behavior, sublethal, lethal). Whereas higher concentrations of a pollutant can easily be assessed with the acute test (which requires lethal concentrations to show an effect), contaminated soils with lower (sublethal) pollutant concentrations require more sensitive test methods such as reproduction or behavioral tests in their risk assessment.     

Nitrogen and Phosphorus Fertilizer Increases the Uptake of Soil Heavy Metal Pollutants by Plant Community

Soil heavy metal pollution is widespread around the world. Compared with hyperaccumulation plants, non-hyperaccumulator plant communities have many advantages in the remediation of heavy metals pollution in soil. The application of nitrogen (N) and phosphorus (P) is inexpensive and convenient, which can promote the growth of plant. N and P fertilizer might increase plant community remediation of heavy metal polluted soils. In our study, the effects of N and P fertilizer on remediation of soil Cd, Cu, Pb pollution by plant community were studied through a greenhouse experiment. Our results indicated that addition of N, P and N?+?P fertilizer increased plant community aboveground biomass. Simultaneously, addition of N and P fertilizer increased the accumulation of heavy metals in aboveground of the plant community and accelerated plants absorption soil heavy metals. Among them, N fertilizer had the best effect. Our results provide an inexpensive method for remediation heavy metal pollution of contaminated farmland, abandoned land and mine tailings, etc.

     

Microbial toxicity tests and chemical analysis as monitoring parameters at composting of creosote-contaminated soil

Traditionally, chemical analyses are used in the assessment of contaminated soil and in monitoring the efficiency of soil remediation processes. We investigated if chemical analysis could be supported and even partly replaced by biological toxicity tests. In two case studies creosote-contaminated soil was composted outdoors in 5- and 100-m3 windrows. Degradation of polyaromatic hydrocarbons (PAHs) was followed by chemical analysis and toxicity tests. Polyaromatic hydrocarbons were quantified and identified by HPLC. Because the soil was also contaminated by copper-, chromium-, and arsenic-containing fungicides, these elements were analyzed by atomic absorption spectrometry. The toxicity of soil samples was assessed by a soil-contact modification of the luminescent bacteria (Vibrio fischeri) test and in the other case also by enzyme synthesis inhibition (Toxi-ChromoPad test, Escherichia coli). The toxicity of soil water extracts was measured by the standard luminescent bacteria (V. fischeri) test and bacterial (Pseudomonas putida) growth inhibition test. After the first 4 months of the composting period the total amount of PAHs was reduced in all windrows, and in particular, the loss of two- and some three-ring compounds was high, almost 90%. Toxicity decreased concurrently with the decrease in PAH concentration during composting, but after 4 months, one of the piles inoculated with mycobacteria and containing more three- and four-ring compounds was found to be more toxic than at the beginning. After the next summer, total PAH content was further reduced but some four-ring or heavier compounds were demonstrated to be poorly degraded. The toxicity was also reduced to the same level as in the control pile. The total PAH content and the toxicity were both reduced significantly during 5 months of composting.     

Terrestrial ecotoxicity of short aliphatic protic ionic liquids

A study of the ecotoxicity of different short aliphatic protic ionic liquids (PILs) on terrestrial organisms was conducted. Tests performed within the present study include those assessing the effects of PILs on soil microbial functions (carbon and nitrogen mineralization) and terrestrial plants. The results show that the nominal lowest-observed-adverse-effect concentration (LOAEC) values were 5,000 mg/kg (dry soil) for the plant test in two species (Lolium perenne, Allium cepa), 1,000 mg/kg (dry soil) for the plant test in one species (Raphanus sativus), and 10,000 mg/kg (dry soil) for carbon and nitrogen microbial transformation tests (all concentrations are nominal). Most of the median effective concentration values (EC50) were above 1,000 mg/kg (dry soil). Based on the obtained results, these compounds can be described as nontoxic for soil microbiota and the analyzed plants, and potentially biodegradable in soils, as can be deduced from the respirometric experiment. The toxicity rises with the increase of complexity of the PILs molecule (branch and length of aliphatic chain) among the three PILs analyzed.     

Toxicities of dinitrotoluenes and trinitrobenzene freshly amended or weathered and aged in a sandy loam soil to Enchytraeus crypticus

Scientifically based ecological soil-screening levels are needed to identify concentrations of contaminant energetic materials (EMs) in soil that present an acceptable ecological risk at a wide range of military installations. Insufficient information regarding the toxicity of 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT), and 1,3,5-trinitrobenzene (TNB) to soil invertebrates necessitated toxicity testing. We adapted the standardized Enchytraeid Reproduction Test (International Standardization Organization 16387:2003) and selected Enchytraeus crypticus for these studies. Tests were conducted in Sassafras sandy loam soil, which supports relatively high bioavailability of nitroaromatic EMs. Weathering and aging procedures for EMs amended to test soil were incorporated into the study design to produce toxicity data that better reflect the soil exposure conditions in the field compared with toxicity in freshly amended soils. This included exposing hydrated, EM-amended soils in open glass containers in the greenhouse to alternating wetting and drying cycles. Definitive tests established that the order of EM toxicity to E. crypticus based on the median effect concentration values for juvenile production in either freshly amended or weathered and aged treatments was (from the greatest to least toxicity) TNB > 2,4-DNT > 2,6-DNT. Toxicity to E. crypticus juvenile production was significantly increased in 2,6-DNT weathered and aged soil treatments compared with toxicity in freshly amended soil, based on 95% confidence intervals. This result shows that future investigations should include a weathering and aging component to generate toxicity data that provide more complete information regarding ecotoxicological effects of energetic contaminants in soil.     

Avoidance tests in site-specific risk assessment--influence of soil properties on the avoidance response of Collembola and earthworms

The ability of organisms to avoid contaminated soils can act as an indicator of toxic potential in a particular soil. Based on the escape response of earthworms and Collembola, avoidance tests with these soil organisms have great potential as early screening tools in site-specific assessment. These tests are becoming more common in soil ecotoxicology, because they are ecologically relevant and have a shorter duration time compared with standardized soil toxicity tests. The avoidance response of soil invertebrates, however, can be influenced by the soil properties (e.g., organic matter content and texture) that affect behavior of the test species in the exposure matrix. Such an influence could mask a possible effect of the contaminant. Therefore, the effects of soil properties on performance of test species in the exposure media should be considered during risk assessment of contaminated soils. Avoidance tests with earthworms (Eisenia andrei) and springtails (Folsomia candida) were performed to identify the influence of both organic matter content and texture on the avoidance response of representative soil organisms. Distinct artificial soils were prepared by modifying quantities of the standard artificial soil components described by the Organization for Economic Co-operation and Development to achieve different organic matter and texture classes. Several combinations of each factor were tested. Results showed that both properties influenced the avoidance response of organisms, which avoided soils with low organic matter content and fine texture. Springtails were less sensitive to changes in these soil constituents compared with earthworms, indicating springtails can be used for site-specific assessments of contaminated soils with a wider range of respective soil properties.     

Monitoring and assessment of mercury pollution in the vicinity of a chloralkali plant. IV. Bioconcentration of mercury in in situ aquatic and terrestrial plants at Ganjam,India

In situ aquatic and terrestrial plants including a few vegetable and crop plants growing in and around a chloralkali plant at Ganjam, India were analyzed for concentrations of root and shoot mercury. The aquatic plants found to bioconcentrate mercury to different degrees included Marsilea spp., Spirodela polyrhiza, Jussiea repens, Paspalum scrobiculatam, Pistia stratiotes, Eichhornia crassipes, Hygrophila schulli, Monochoria hastata and Bacopa monniera. Among wild terrestrial plants Chloris barbata, Cynodon dactylon, Cyperus rotundus and Croton bonplandianum were found growing on heavily contaminated soil containing mercury as high as 557 mg/kg. Analysis of mercury in root and shoot of these plants in relation to the mercury levels in soil indicated a significant correlation between soil and plant mercury with the exception of C. bonplandianum. Furthermore, the tolerance to mercury toxicity was highest with C. barbata followed by C. dactylon and C. rotundus, in that order. The rice plants analyzed from the surrounding agricultural fields did not show any significant levels of bioconcentrated mercury. Of the different vegetables grown in a contaminated kitchen garden with mercury level at 8.91 mg/kg, the two leafy vegetables, namely cabbage (Brassica oleracea) and amaranthus (Amaranthus oleraceous), were found to bioconcentrate mercury at statistically significant levels. The overall study indicates that the mercury pollution is very much localized to the specific sites in the vicinity of the chloralkali plant.     

Compost-Mediated Removal of Polycyclic Aromatic Hydrocarbons from Contaminated Soil

Compost-assisted remediation of a manufactured-gas plant soil contaminated with polycyclic aromatic hydrocarbons (PAHs) was performed in thermally insulated composting chamber using mushroom compost consisting wheat straw, chicken manure, and gypsum. The degradation of individual PAHs was in range of 20–60% at the end of 54 days of composting followed by further increase of PAH removal (37–80%) after another 100 days of maturation. Both chemical analysis of the contaminated soil for PAHs and ecotoxicity tests on bioluminescent bacteria, earthworms, and plant seeds were performed before and after the composting. After the composting, inhibition of bioluminescence decreased, whereas no significant change in toxicity was observed for earthworm survival and seed germination. Using bacterial culture of Escherichia coli K12 genotoxicity tests were performed on samples taken from different parts of the composting pile; after the composting the decrease in genotoxicity was observed only in the sample taken from upper part of the composted pile. Received: 2 March 2002/Accepted: 12 June 2002     

A Phytotoxicity Test Using Transpiration of Willows

A short-term acute toxicity assay for willow trees growing in contaminated solution or in polluted soil was developed and tested. The test apparatus consists of an Erlenmeyer flask with a prerooted tree cutting growing in it. Growth and reduction of transpiration are used to determine toxicity. Transpiration is closely related to photosynthesis and growth, but is easier and faster to measure and can be measured without disturbance of the test system. Plants are grown for 24 h in uncontaminated nutrient solution before the toxicant is added to determine the initial transpiration. The loss of weight is expressed as % decrease after 48 and 72 h or longer compared to the initial transpiration, divided by the transpiration of control plants. More toxicity parameters are growth and water use efficiency of the plants. The sensitivity of the test was evaluated with 3,5-dichlorophenol. EC₅₀ values between 5.8 and 9.6 mg/L were found. This is similar to the results from algal growth rate tests. The willow tree toxicity test may be useful for determining the site-specific toxicity of polluted soils and for terrestrial risk assessment of new chemicals and pesticides. Received: 8 November 1999/Accepted: 28 February 2000     

土壤中重金属对人体生物有效性的体外试验评估

由于经由食物链进入人体的重金属的途径和危害已得到相当充分的认识,并开始得到有效的控制和削减,人体经口直接摄入土壤中的重金属已成为人体重金属总摄入量的重要来源。评估经口摄入重金属的人体生物有效性的传统方法是动物实验。与动物实验相比,体外试验具有实验周期短、费用低和结果重现性好等优点,且二者的实验结果具有很好的相关性。该文着重介绍体外试验的发展和现状,并简述其基本实验方法。该法不仅可通过评估土壤重金属的人体生物有效性,为制定更为全面地保障人体健康的土壤质量标准或清洁标准提供科学依据,而且可以用来快速评价污染土壤修复措施的效果。该法因其独特的优点在发达国家得到越来越多的重视和应用,因此,可以预期该法在我国土壤污染的风险评估和控制措施的评价中也将有较为广阔的应用前景。     

Health risk-based assessment and management of heavy metals-contaminated soil sites in Taiwan

Risk-based assessment is a way to evaluate the potential hazards of contaminated sites and is based on considering linkages between pollution sources, pathways, and receptors. These linkages can be broken by source reduction, pathway management, and modifying exposure of the receptors. In Taiwan, the Soil and Groundwater Pollution Remediation Act (SGWPR Act) uses one target regulation to evaluate the contamination status of soil and groundwater pollution. More than 600 sites contaminated with heavy metals (HMs) have been remediated and the costs of this process are always high. Besides using soil remediation techniques to remove contaminants from these sites, the selection of possible remediation methods to obtain rapid risk reduction is permissible and of increasing interest. This paper discusses previous soil remediation techniques applied to different sites in Taiwan and also clarified the differences of risk assessment before and after soil remediation obtained by applying different risk assessment models. This paper also includes many case studies on: (1) food safety risk assessment for brown rice growing in a HMs-contaminated site; (2) a tiered approach to health risk assessment for a contaminated site; (3) risk assessment for phytoremediation techniques applied in HMs-contaminated sites; and (4) soil remediation cost analysis for contaminated sites in Taiwan.     

Weathering and aging of 2,4,6-trinitrotoluene in soil increases toxicity to potworm Enchytraeus crypticus

Energetic materials are employed in a wide range of commercial and military activities and often are released into the environment. Scientifically based ecological soil-screening levels (Eco-SSLs) are needed to identify contaminant explosive levels in soil that present an acceptable ecological risk. Insufficient information for 2,4,6-trinitrotoluene (TNT) to generate Eco-SSLs for soil invertebrates necessitated toxicity testing. We adapted the standardized Enchytraeid Reproduction Test and selected Enchytraeus crypticus for these studies. Tests were conducted in Sassafras sandy loam soil, which supports relatively high bioavailability of TNT. Weathering and aging procedures for TNT amended to test soil were incorporated into the study design to produce toxicity data that better reflect the soil exposure conditions in the field compared with toxicity in freshly amended soils. This included exposing hydrated TNT-amended soils in open glass containers in the greenhouse to alternating wetting and drying cycles. Definitive tests showed that toxicity for E. crypticus adult survival and juvenile production was increased significantly in weathered and aged soil treatments compared with toxicity in freshly amended soil based on 95% confidence intervals. The median effect concentration and 20% effective concentration for reproduction were 98 and 77 mg/kg, respectively, for TNT freshly amended into soil and 48 and 37 mg/kg, respectively, for weathered and aged TNT soil treatments. These findings of increased toxicity to E. crypticus in weathered and aged TNT soil treatments compared with exposures in freshly amended soils show that future investigations should include a weathering and aging component to generate toxicity data that provide more complete information on ecotoxicological effects of energetic contaminants in soil.     

Assessment of the Suitability of Phytotoxkit Plastic Vertical Containers Compared with Petri Dishes for Standard Seedling Growth Tests

This study compares two cultivation methods (Petri dishes vs. Phytotoxkit containers; tap water vs. Knop’s solution) for standard seedling growth tests. Seeds and young seedlings of Sinapis alba and Hordeum vulgare were used as study subjects and the adverse effect of Cd was assessed. Under testing conditions, only H. vulgare showed a significant decrease in seed germination in Petri dishes when tap water was used as the growth medium (70.8 % ± 46.4 %). No significant differences in IC₅₀ values were found in either plant type for root growth between plants cultivated in Phytotoxkit containers and those cultivated in Petri dishes. The same findings were confirmed for shoot growth in H. vulgare, but not in S. alba. Suitability of Phytotoxkit containers over traditionally used Petri dishes for phytotoxicity determination was confirmed by higher correlation coefficients for all tests.     

Effects of metal-contaminated forest soils from the Canadian shield to terrestrial organisms

The effects of elevated metal concentrations in forest soils on terrestrial organisms were investigated by determining the toxicity of six site soils from northern Ontario and Quebec, Canada, using a battery of terrestrial toxicity tests. Soils were collected from three sites on each of two transects established downwind of nickel (Sudbury, ON, Canada) and copper (Rouyn-Noranda, PQ, Canada) smelting operations. Site soils were diluted to determine if toxicity estimates for the most-contaminated site soils could be quantified as a percent of site soil. Rouyn-Noranda soils were toxic following acute exposure (14 d) to plants, but not to invertebrates (7 d for collembola and 14 d for earthworms). However, Rouyn-Noranda soils were toxic to all species following chronic exposure (21, 35, and 63 d for plants, collembola, and earthworms, respectively). The toxicity of the Rouyn-Noranda site soils did not correspond to the gradient of metal concentrations in soil. Metal-contaminated Sudbury soils were toxic to plants but not to invertebrates, following acute exposure. Chronic exposure to Sudbury soils caused adverse effects to plant growth and invertebrate survival and reproduction. The toxicity of Sudbury soils corresponded to the metal concentration gradient, with one exception: The reference soil collected in October was toxic to collembola following acute and chronic exposure. This study evaluated the applicability of the new Environment Canada terrestrial toxicity test methods, developed using agricultural soils, to forest soils and also provided useful data to assess the ecological risk associated with mixtures of metals in soil.     

Real-Time Fit of a Respirator during Simulated Health Care Tasks

Fit is an important but difficult-to-predict feature of respirator performance. This study examined a new approach to measuring respirator performance using two continuous direct-reading particle-counting instruments in a simulated health care workplace. A pilot test was conducted with eight experienced health care professionals who passed a traditional quantitative fit test before performing three randomized 10-min health care scenarios (patient assessment [PA], IV treatment [IV], and wound care [WC]). Two TSI Portacount Plus (Model 8020) with N95 Companion (Model 8095) instruments were used to continuously measure 1-sec ambient particle concentrations inside and outside the respirator facepiece. A simulated workplace protection factor (SWPF) was calculated by dividing outside by inside concentrations. Data were log transformed and examined using analysis of variance (ANOVA) between subjects, scenario types, and scenario order. The GM SWPF for the eight subjects, three scenarios per subject, ranged from 172 to 1073 (GSD 1.7 to 3.5) and was significantly different for each subject. A multi-way analysis of variance showed no difference between the three scenario types (PA, IV, WC). There were differences by the order in which scenarios were performed: the third scenario SWPF was significantly different and higher than that of the first and second scenarios. All subjects passed the initial quantitative fit test with a fit factor of at least 100. Five subjects had fit factors greater than 200 and GM scenario SWPFs greater than 400. Three participants with initial fit factors less than 200 had GM scenario SWPFs ranging from 132 to 326. This pilot test demonstrates that it is possible to evaluate instantaneous respirator fit using two quantitative fit test instruments in a simulated health care environment. Results suggest that an initial fit test may be predictive of fit during simulated tasks and that one scenario may be adequate for measuring a simulated workplace protection factor. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resource: a video for subject D activities overlaid with simulated workplace protection factor data.].