Toxicity Of Boric Acid Research Articles

Evaluation of Possible Toxic Effects of Boric Acid in Palourde Clam (Ruditapes decussatus) Through Histological Changes and Oxidative Responses.

The extensive utilization of boric acid, particularly in industrial and agricultural sectors, also engenders concerns regarding the toxicity of boron and its derivatives. Particularly, the behavior of boric acid at increasing concentrations in aquatic ecosystems remains poorly understood. In light of these concerns, this study aimed to investigate the toxicity of boric acid in bivalves, which occupy a critical position in the food chain. Specimens of Ruditapes decussatus, which had not been previously exposed to any pollutants and were cultivated under controlled conditions, were subjected to three different concentrations of boric acid (0.05mg/L, 0.5mg/L, and 5mg/L) in vitro for 96h. Following the exposure period, the specimens were assessed for histological changes (the mantle, gill, and digestive gland) and specific oxidative parameters (the gill and digestive gland), including superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase, and lipid peroxidation (LPO). The research findings indicated that boric acid primarily induced oxidative damage at the applied concentrations and increased antioxidant levels (p < 0.05). Moreover, although no significant histopathological abnormalities were observed in the examined histological sections, subtle changes were noted. This study evaluated the potential adverse effects of boric acid on bivalves, which are crucial components of the aquatic food chain, utilizing histological and specific physiological parameters following its introduction into aquatic environments. It is anticipated that the findings of this study will contribute to the development of new insights and perspectives regarding the extensive use of boric acid.

Genome-Wide Screens Identify Genes Responsible for Intrinsic Boric Acid Resistance in Escherichia coli.

Boric acid (BA) has antimicrobial properties and is used to combat bacterial infections, including Enterobacteria. However, the molecular mechanisms and cellular responses to BA are still unknown. This genomics study aims to provide new information on the genes and molecular mechanisms related to the antimicrobial effect of BA in Escherichia coli. The Keio collection of E. coli was used to screen 3985 single-gene knockout strains in order to identify mutant strains that were sensitive or hypersensitive to BA at certain concentrations. The mutant strains were exposed to different concentrations of BA ranging from 0 to 120mM in LB media. Through genome-wide screens, 92 mutants were identified that were relatively sensitive to BA at least at one concentration tested. The related biological processes in the particular cellular system were listed. This study demonstrates that intrinsic BA resistance is the result of various mechanisms acting together. Additionally, we identified eighteen out of ninety-two mutant strains (Delta_aceF, aroK, cheZ, dinJ, galS, garP, glxK, nohA, talB, torR, trmU, trpR, yddE, yfeS, ygaV, ylaC, yoaC, yohN) that exhibited sensitivity using other methods. To increase sensitivity to BA, we constructed double and triple knockout mutants of the selected sensitive mutants. In certain instances, engineered double and triple mutants exhibited significantly amplified effects. Overall, our analysis of these findings offers further understanding of the mechanisms behind BA toxicity and intrinsic resistance in E. coli.

Exploring the mechanisms underlying the toxicity of boric acid against the land snail, Theba pisana.

The land snail, Theba pisana, is one of the most important threats facing agriculture around the globe. Boric acid (BOA) is currently used as a safe alternative molluscicide to control land snails in sustainable agriculture, but the mechanisms of toxicity have not yet been investigated. The present study characterizes the lethal and sub-lethal (0.5 and 1mg g-1 ) toxic effects of BOA-contaminated food for 14 days by examining physiological, biochemical and histopathological indicators in T. pisana to understand the mechanisms underlying its toxic action. BOA was found to be lethal against T. pisana with LC50 values of 24.7 and 8.05 mg g-1 after 3 and 7 days of exposure, respectively. BOA sublethal concentrations led to a significant reduction in food consumption and growth of snails after 14 days of exposure. BOA also caused a significant increase in testosterone levels, whereas an opposite effect was observed in estradiol levels. An increase in progesterone levels in snails in the 0.5mg g-1 BOA group and a decrease in the 1mg g-1 BOA group were observed after all exposure times. Moreover, the lipid peroxidation level and catalase activity were elevated, whereas acetylcholinesterase activity was inhibited in the treated snails. Alteration in glutathione-S-transferase activity was noticed after exposure to both sublethal concentrations. In addition, BOA induced histopathological alterations in the digestive gland of T. pisana. Our findings provide novel insights into how physiological, biochemical and histopathological alterations can be used to explore the mechanisms underlying BOA toxicity against snails. © 2022 Society of Chemical Industry.

Boric acid toxicity in some selected molluscan species

: Survivability of animals is correlated with their fecundity and fertility success. Widespread use of enormous organic and inorganic ingredients as pesticides, molluscicides and insecticides contaminate ecosystems leading to hazardous effects on the life cycle of animals, their biological processes and reproduction. Present work aimed for toxicity assessment of boric acid against some selected molluscan species through evaluation of their mortality by determination of LC50. For toxicity assessment three different molluscan species were used. By applying standard procedure, LC50 was estimated at different concentrations of boric acid for different exposure periods. This study indicated that freshwater snail Bellamya bengalensis was more sensitive for boric acid, whereas slug, Semperula maculate was least sensitive against boric acid after different period of exposure.

Boric acid was orally toxic to different instars of Blattella germanica (L.) (Blattodea: Blattellidae) and caused dysbiosis of the, gut microbiota

Boric acid, a well-established chemical insecticide, has a good control effect on various types of cockroaches. In this study, we investigated the oral virulence effect of boric acid on German cockroach (Blattella germanica) of various instars and characterized its effect on the gut microbiota by high-throughput sequencing technology. The results of an oral toxicity test showed that the toxicity of boric acid was positively correlated with its concentration and negatively correlated with the instar of cockroach nymphs. The 1–3 instar nymphs showed the strongest sensitivity to boric acid, which exhibited a median lethal time of only 3.16 d, while the 6–7 instar nymphs showed the weakest sensitivity, and exhibited a median lethal time of 10.15 d. There was no significant difference between male and female insects regarding their sensitivity to boric acid. Oral treatment of boric acid resulted in severe dysbiosis in cockroaches, the relative abundances of Bacteroides, which can degrade a variety of complex macromolecules, and Enterococcus, which can inhibit pathogenic microorganisms, were significantly reduced, while the relative abundance of the opportunistic pathogenic bacterium Weissella was significantly increased. It was speculated that dysbiosis of gut microbiota might accelerate the toxicity of boric acid on German cockroaches.

Abiotic stress caused by foliar applications of boron to the yellow diploid potato (Solanum tuberosum, Group Phureja) cultivar Criolla Galeras

Foliar applications of boron (B) constitute a frequent practice in the fertilization of the yellow diploid potato and are generally done with excessive and empirical doses generating toxicities in crops. The effect of foliar applications of B at doses of 0, 0.5, 1.2, or 4 kg ha-1 was determined for physiological and metabolic variables and toxicity symptoms in the yellow diploid potato cultivar Criolla Galeras under greenhouse conditions using Na octaborate (20.5% B, 11% Na) or boric acid (17.5% B) as sources of B. Significant differences (P&lt;0.05) were found between the sources and doses for dry matter (DW), leaf area (LA), proline content, and electrolyte leakage (ECh). The highest toxicity was observed for B applied as sodium octaborate at concentrations of 2 and 4 kg ha-1 B with a reduction of DM up to 40%, a decrease of LA up to 90%, a loss of 60% in ECh, and a significant increase in the concentration of proline (65 μmol/g fresh weight). The lower toxicity of boric acid at doses higher than 2 kg ha-1 B indicated that the octaborate Na presented synergism with B, which can result in a greater oxidative stress, causing instability of the membranes, necrosis and premature tissue death, as evidenced in the description of the visual symptoms. The doses of 0.5 and 1.0 kg ha-1 B for both sources resulted in positive responses in the DW and non-significant (P&lt;0.05) differences with the control, associated with the levels of proline and ECh, which indicated a narrow range between the deficiency and toxicity of B for cv. Criolla Galeras, where the effect of the accompanying ion must be considered in the selection of the boron source.

Influence of boric acid on energy metabolism and stress tolerance of Candida albicans

Boron presents at physiological pH in the form of boric acid (BA), a molecule that has both positive and negative effects on biological processes. In medicine, BA is used as a topical treatment for vaginal yeast infections by Candida species because of its well-documented but poorly understood effect on inhibition of growth in general and of invasive, hyphal growth in particular. The present study examines the influence of BA on carbohydrate energy metabolism of this common human pathogen. Starting from previous findings about an inhibition of key NAD-dependent enzymes by BA in vitro, we confirmed that such an inhibition occurs in permeabilized C. albicans cells. Cultures growing even with moderate concentrations of BA experience mitochondrial failure, increase ethanol production from glucose and decrease the deposition of carbohydrate stores in the form of glycogen. Cells growing on the non-fermentable, FAD-generating carbon source lactate have a higher BA tolerance, which suggests that the toxicity of BA is rooted in an inhibition of NAD-dependent reactions and the increased production of ethanol. Boric acid exposure sensitizes C. albicans selectively to the toxic effects of ethanol. This additive effect suggests that the endogenously produced ethanol increases the load on ethanol resistance mechanisms. Lastly, combination studies showed no interactions of BA with common antifungal drugs, meaning that addition of BA to topical formulations can provide an additive antifungal effect regardless of the chosen active ingredient.

Loci Contributing to Boric Acid Toxicity in Two Reference Populations of Drosophila melanogaster.

Populations maintain considerable segregating variation in the response to toxic, xenobiotic compounds. To identify variants associated with resistance to boric acid, a commonly-used household insecticide with a poorly understood mechanism of action, we assayed thousands of individuals from hundreds of strains. Using the Drosophila Synthetic Population Resource (DSPR), a multi-parental population (MPP) of inbred genotypes, we mapped six QTL to short genomic regions containing few protein-coding genes (3–188), allowing us to identify plausible candidate genes underlying resistance to boric acid toxicity. One interval contains multiple genes from the cytochrome P450 family, and we show that ubiquitous RNAi of one of these genes, Cyp9b2, markedly reduces resistance to the toxin. Resistance to boric acid is positively correlated with caffeine resistance. The two phenotypes additionally share a pair of QTL, potentially suggesting a degree of pleiotropy in the genetic control of resistance to these two distinct xenobiotics. Finally, we screened the Drosophila Genetic Reference Panel (DGRP) in an attempt to identify sequence variants within mapped QTL that are associated with boric acid resistance. The approach was largely unsuccessful, with only one QTL showing any associations at QTL-specific 20% False Discovery Rate (FDR) thresholds. Nonetheless, these associations point to a potential candidate gene that can be targeted in future validation efforts. Although the mapping data resulting from the two reference populations do not clearly overlap, our work provides a starting point for further genetic dissection of the processes underlying boric acid toxicity in insects.

Boric Acid Inhibition of Trichophyton rubrum Growth and Conidia Formation.

Trichophyton rubrum is a common human dermatophyte that is the causative agent of 80-93% of fungal infections of the skin and nails. While dermatophyte infections in healthy people are easily treatable with over-the-counter medications, such infections pose a higher risk for patients with compromised immune function and impaired regenerative potential. The efficacy of boric acid (BA) for the treatment of vaginal yeast infections prompted an investigation of the effect of BA on growth and morphology of T. rubrum. This is of particular interest since BA facilitates wound healing, raising the possibility that treating athlete's foot with BA, either alone or in combination with other antifungal drugs, would combine the benefits of antimicrobial activity and tissue regeneration to accelerate healing of infected skin. The data presented here show that BA represses T. rubrum growth at a concentration reported to be beneficial for host tissue regeneration. Oxygen exposure increases BA toxicity, and mycelia growing under BA stress avoid colonizing the surface of the growth surface, which leads to a suppression of aerial mycelium growth and surface conidia formation. BA penetrates into solid agar matrices, but the relative lack of oxygen below the substrate surface limits the effectiveness of BA in suppressing growth of embedded T. rubrum cells.

Reproductive toxicity of boric acid and sodium borates

Reproductive toxicity of boric acid and sodium borates

Boric Acid Is Reproductively Toxic to AdultXenopus laevis, but Not Endocrine Active

The potential reproductive and endocrine toxicity of boric acid (BA) in the African clawed frog, Xenopus laevis, was evaluated using a 30-day exposure of adult frogs. Adult female and male frogs established as breeders were exposed to a culture water control and 4 target (nominal) test concentrations [5.0, 7.5, 10.0, and 15 mg boron (B)/L, equivalent to 28.5, 42.8, 57.0, and 85.5 mg BA/L] using flow-through diluter exposure system. The primary endpoints measured were adult survival, growth (weight and snout-vent length [SVL]), necropsy data, reproductive fecundity, and development of progeny (F1) from the exposed frogs. Necropsy endpoints included gonad weight, gonado-somatic index (GSI), ovary profile (oocyte normalcy and stage distribution), sperm count, and dysmorphology. Endocrine endpoints included plasma estradiol (E2), testosterone (T), dihydrotestosteone (DHT), gonadal CYP 19 (aromatase), and gonadal 5α-reductase (5-AR). BA exposure to adult female X. laevis increased the proportion of immature oocytes (< stage II) in the ovaries of females, reduced sperm counts and increased sperm cell dysmorphology frequency in male frogs exposed to 15 mg B/L. No effects on the other general, developmental (F1), or endocrine endpoints were observed. Based on the results of the present study, the no observed adverse effects concentration (NOAEC) for the reproductive endpoints was 10 mg B/L; and 15 mg B/L for reproductive fecundity, F1 embryo larval development, and endocrine function. These results confirmed that although BA is capable of inducing reproductive toxicity at high concentrations, it is not an endocrine disrupting agent.

Protective Effect of Boric Acid on Oxidative DNA Damage In Chinese Hamster Lung Fibroblast V79 Cell Lines.

Many studies have been published on the antioxidative effects of boric acid (BA) and sodium borates in in vitro studies. However, the boron (B) concentrations tested in these in vitro studies have not been selected by taking into account the realistic blood B concentrations in humans due to the lack of comprehensive epidemiological studies. The recently published epidemiological studies on B exposure conducted in China and Turkey provided blood B concentrations for both humans in daily life and workers under extreme exposure conditions in occupational setting. The results of these studies have made it possible to test antioxidative effects of BA in in vitro studies within the concentra- tion range relevant to humans. The aim of this study was to investigate the protective ef- fects of BA against oxidative DNA damage in V79 (Chinese hamster lung fibroblast) cells. The concentrations of BA tested for its protective effect was selected by taking the blood B concentrations into account reported in previously published epidemiological studies. Therefore, the concentrations of BA tested in this study represent the exposure levels for humans in both daily life and occupational settings. In this experimental study, comet assay and neutral red uptake (NRU) assay methods were used to determinacy to toxicity and genotoxicity of BA and hydrogen peroxide (H2O2). The results of the NRU assay showed that BA was not cytotoxic within the tested concentrations (3, 10, 30, 100 and 200 µM). These non-cytotoxic concentrations were used for comet assay. BA pre-treatment significantly reduced (P<0.05, one-way ANOVA) the DNA damaging capacity of H2O2 at each tested BA concentrations in V79 cells. Consequently, pre-incubation of V79 cells with BA has significantly reduced the H2O2-induced oxidative DNA damage in V79 cells. The protective effect of BA against oxidative DNA damage in V79 cells at 5, 10, 50, 100 and 200 μM (54, 108, 540, 1080, and 2161 ng/ml B equivalents) concentrations was proved in this in vitro study.

The Antimicrobial Effect of Boric Acid on Trichomonas vaginalis

The treatment options for trichomoniasis are largely limited to nitroimidazole compounds (metronidazole and tinidazole). Few alternatives exist in cases of recalcitrant infections or in cases of nitroimidazole hypersensitivity. Recently, the intravaginal administration of boric acid has been advocated as an alternative treatment of trichomoniasis. However, no in vitro studies are available that directly assess the sensitivity of Trichomonas vaginalis to boric acid. We examined the sensitivity of common laboratory strains and recent clinical isolates of T. vaginalis to boric acid. The effect of increasing concentrations of boric acid on parasite growth and viability was determined, and a minimal lethal concentration was reported. The effect of pH on boric acid toxicity was assessed and compared with that of lactic and acetic acid. Boric acid is microbicidal to T. vaginalis, and its antitrichomonal activity is independent of environmental acidification. Unlike acetic acid and lactic acid, boric acid exposure results in growth suppression and lethality over a wide range of pH (5-7) and under conditions that are normally permissible for growth in vitro. The microbicidal effect of boric acid on T. vaginalis, coupled with its previous clinical use in treating vaginal candidiasis, supports the continued inclusion of boric acid in the therapeutic arsenal for treating trichomoniasis.

Immobilized bacteria by using PVA (Polyvinyl alcohol) crosslinked with Sodium sulfate

A new bacteria immobilization technique using PVA (polyvinyl alcohol) crosslink with sodium sulfate was developed. This new technique can simultaneously eliminate the agglomeration of PVA beads and the toxicity of boric acid caused by the PVA-boric methods, also reducing the swelling (when soaking in water) of PVA-boric methods. Beads were immobilized by using four different PVA immobilization processes to create group B, group N, group P and group S. The stability, swelling, relative mechanical strength of these kinds of beads were compared in this study. Only group S was the best and chosen to do experiment for checking survival of bacteria after immobilization process and TOC removal performance of anaerobic reactor. The TOC removal performance of anaerobic reactor achieved 80-87%.

Multiple Organ Damage Due to Boric Acid Toxicity

Background: Boric acid (BA) is commonly used as pesticide, disinfectant and wood preservative. Its ingestion can cause serious organ damages resulting in death. Case report: A 19 year old man was found dead with two empty packs of BA tablets in vicinity of his body. On autopsy examination, brownish stains along with right angle of mouth and right nostril were found. Stomach was damaged with hemorrhagic gastritis. All internal organs including liver, kidney, spleen and brain were congested. The toxicological analysis of viscera confirmed boron ion toxicity. Discussion: Boric acid is a moderately toxic compound that is a mucosal corrosive agent affecting upper respiratory and gastrointestinal tracts. It can also act as a generalized cellular poison, and thus all end organs including liver, kidneys, brain and gastrointestinal tract are prone to its toxicity. Massive BA poisoning mostly occurs in adults as a result of suicide attempt. Early aggressive hydration and hemodialysis can prevent its mortality. Conclusion: A dead body with erythematous rash, redness of skin, bluish green color of vomitus and fecal matter, corrosive changes in oral and nasal cavity and multiple organ damages can be highly suggestive of BA poisoning. How to cite this article: Rani M, Meena MC. Multiple Organ Damage Due to Boric Acid Toxicity. Asia Pac J Med Toxicol 2013;2:157-9.

Human Environmental and Occupational Exposures to Boric Acid: Reconciliation with Experimental Reproductive Toxicity Data

The reproductive toxicity of boric acid and borates is a matter of current regulatory concern. Based on experimental studies in rats, no-observed-adverse-effect levels (NOAELs) were found to be 17.5 mg boron (B)/kg body weight (b.w.) for male fertility and 9.6 mg B/kg b.w. for developmental toxicity. Recently, occupational human field studies in highly exposed cohorts were reported from China and Turkey, with both studies showing negative results regarding male reproduction. A comparison of the conditions of these studies with the experimental NOAEL conditions are based on reported B blood levels, which is clearly superior to a scaling according to estimated B exposures. A comparison of estimated daily B exposure levels and measured B blood levels confirms the preference of biomonitoring data for a comparison of human field studies. In general, it appears that high environmental exposures to B are lower than possible high occupational exposures. The comparison reveals no contradiction between human and experimental reproductive toxicity data. It clearly appears that human B exposures, even in the highest exposed cohorts, are too low to reach the blood (and target tissue) concentrations that would be required to exert adverse effects on reproductive functions.

Boric Acid Toxicity Trials on the Wood Borer &lt;i&gt;Heterobostrychus aequalis&lt;/i&gt; Waterhouse (Coleoptera: Bostrychidae)

: Problem statement: The Heterobostrychus aequalis Waterhouse was a serious pest lumber of timber heveawood. The H. aequalis infest and tunnel along the wood grain, depositing eggs, which concomitantly turn into larvae and reduces the wood starch to a soft powder. The objectives of the study were to establish a suitable method for preservative trials on the wood borer and access the toxicity levels of boric acid for controlling the H. aequalis infestation. Approach: The voracious H. aequalis was collected from infested heveawood, mated and cultured on cassava. The adult beetles were exposed to boric acid treated cassava blocks as pilot trials. The boric acid concentration used was 1-5% including a control. Each treatment consists of five replicates. The voracious of H. aequalis generation was cultured for obtaining its freshly new emerged adult by exposing a number of H. aequalis directly from infested heveawood into artificial diet block and cassava. The mortality, weight loss of the test blocks, frass discharge duration and numbers of holes caused by H. aequalis were observed. Results: The results showed that the H. aequalis infested tended to penetrate the film after wrapping the heveawood with a layer of transparent cling film for 24 h experiment. The H. aequalis larvae stock cultured collected from infested heveawood exhibited differences in colour, activeness and aggression among males and females. The suitable test block size used was (2.0×5.0×1.5) cm3. The freshly emerged voracious of H. aequalis adults was more suitable than the larvae for boric acid toxicity trials. The 2% concentration was sufficiently killed the 4% boric acid treated test blocks. There was no hole observed on 5% boric acid treated test block and hence these concentrations were not infested by H. aequalis due to absence of frass in exposed blocks. Conclusion/Recommendations: There are noticeable physical and behavioural differences between voracious of H. aequalis collected from infested heveawood. The freshly emerged of H. aequalis adults were found suitable than the larvae as an indicator for determining the boric acid toxicity trials. The 5% of boric acid concentration was sufficient to control the infection of H. aequalis on heveawood. Further studies focusing on interaction between larvae, adults and population growth of H. aequalis with different hosts need to be carried out towards clarifying the predisposing factors that induce the infestation processes.

“Boiled lobster” rash of acute boric acid toxicity

A 45-year-old male with a history of schizophrenia presented to the emergency department after ingesting a large glass of pesticide composed of boric acid mixed with water in response to auditory h...

Boric acid inhibits stored Ca2+ release in DU-145 prostate cancer cells

Boron (B) is a developmental and reproductive toxin. It is also essential for some organisms. Plants use uptake and efflux transport proteins to maintain homeostasis, and in humans, boron has been reported to reduce prostate cancer. Ca2+ signaling is one of the primary mechanisms used by cells to respond to their environment. In this paper, we report that boric acid (BA) inhibits NAD+ and NADP+ as well as mechanically induced release of stored Ca2+ in growing DU-145 prostate cancer cells. Cell proliferation was inhibited by 30% at 100 microM, 60% at 250 microM, and 97% at 1,000 microM BA. NAD+-induced Ca2+ transients were partly inhibited at 250 microM BA and completely at 1,000 microM BA, whereas both NADP+ and mechanically induced transients were inhibited by 1,000 microM BA. Expression of CD38 protein increased in proportion to BA exposure (0-1,000 microM). In vitro mass spectrometry analysis showed that BA formed adducts with the CD38 products and Ca2+ channel agonists cyclic adenosine diphosphate ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP). Vesicles positive for the Ca2+ fluorophore fluo-3 acetoxymethyl ester accumulated in cells exposed to 250 and 1,000 microM BA. The BA analog, methylboronic acid (MBA; 250 and 1,000 microM), did not inhibit cell proliferation or NAD+, NADP+, or mechanically stimulated Ca2+ store release. Nor did MBA increase CD38 expression or cause the formation of intracellular vesicles. Thus, mammalian cells can distinguish between BA and its synthetic analog MBA and exhibit graded concentration-dependent responses. Based on these observations, we hypothesize that toxicity of BA stems from the ability of high concentrations to impair Ca2+ signaling.

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.