Short-term exposure of zooplankton to the synthetic pyrethroid,fenvalerate, and its effects on rates of filtration and assimilation of the alga,Chlamydomonas reinhardii

In acute tests of toxicity, two cladocerans,Daphnia galeata mendotae andCeriodaphnia lacustris, and the calanoid,Diaptomus oregonensis, were more sensitive to fenvalerate thanDaphnia magna, the organism used in standard laboratory bioassays. The 48-hr EC₅₀s for each species/stage in order of increasing sensitivity were adultD. magna — 2.52 g/L;D. magna (48-hr old) — 0.83 g/L; adultD. galeata mendotae — 0.29 g/L; adultC. lacustris — 0.21 g/L;D. galeata mendotae (48-hr old) — 0.16 g/L; adultDiaptomus oregonensis — –0.12 g/L. No toxicity was observed when these organisms were exposed to a range of concentrations of the emulsifiable concentrate without fenvalerate (the EC blank).Rates of filtration of the¹⁴C-labelled alga,Chlamydomonas reinhardii byD. galeata mendotae, C. lacustris andD. oregonensis were decreased significantly at sublethal concentrations of fenvalerate after only 24-hr exposure.Ceriodaphnia lacustris showed the greatest sensitivity with rates of filtration significantly decreased at 0.01 g fenvalerate/ L. Concentrations of fenvalerate 0.05 g/L resulted in decreased rates of filtration byD. galeata mendotae. A concentration of 0.10 g fenvalerate/ L caused rates of filtration to increase inD. oregonensis. whereas 0.05 and 0.5 g/L resulted in a decrease in these rates.Rates of assimilation of algae byD. galeata mendotae, C. lacustris andD. oregonensis exposed to similar concentrations of fenvalerate were decreased at concentrations 0.05 g fenvalerate/L. Changes in rates of assimilation were not as sensitive a parameter of toxicity as changes in rates of filtration. The EC blank had no significant effects on rates of filtration or assimilation for all three species.     

Sublethal Effects of Trace Metals (Cd,Cr, Cu,Hg) on Embryogenesis and Larval Settlement of the Ascidian <Emphasis Type="Italic">Ciona intestinalis</Emphasis>

Toxicity of Cadmium (Cd), Chromium (Cr), Copper (Cu), and Mercury (Hg) on the early developmental stages of Ciona intestinalis was investigated. Developmental defects of larvae after exposure of gametes throughout their development to the larval stage were assessed. Gamete exposure to increasing metal concentrations resulted in a significant decrease of the percentage of normally hatched larvae, showing median effective concentrations (EC₅₀) of 721 g/L (6.42 M) for Cd, 12772 g/L (226 M) for Cr, 36.6 g/L (0.576 M) for Cu, and 44.7 g/L (0.223 M) for Hg. Larval attachment was significantly affected when gametes were exposed to the metals throughout development. The EC₅₀ reducing larval attachment by 50% were 752 g/L (6.7 M) for Cd, 15026 g/L (289 M) for Cr, 67.8 g/L (1.607 M) for Cu, and 78.1 g/L (0.389 M) for Hg. Therefore, on a molar basis Hg is three times more toxic than Cu, 20–30 times more than Cd, and 700–1000 times more toxic than Cr, for both responses.     

Development of a Sublethal Test to Determine the Effects of Copper and Lead on Scleractinian Coral Larvae

A new sublethal toxicity test was developed in this study to measure the effect of copper and lead on the motility of coral larvae. Larval motility was significantly affected by copper and lead doses immediately after dosing. The copper EC₅₀ values for motility of Goniastrea aspera brain coral larvae (12 h, 21 g/L; 24 h, 16 g/L; 48 h, 22 g/L) were much lower than the copper LC₅₀ values for G. aspera larval survival (6 h, 260 g/L, and 24 h, 121 g/L, for 5-day-old larvae and 6 h, 248 g/L, and 24 h, 136.64 g/L, for 6-day-old larvae) during the early part of the experiments. However, at later times, the LC₅₀ values (48 h, 40 g/L, for 5-day-old larvae and 48- h, 87 g/L, for 6-day-old larvae) were similar to the EC₅₀ values for larval motility. The lead 72-h EC₅₀ value for G. aspera larval motility (2900 g/L) was much lower than the lead 72-h LC₅₀ value for larval survival (9890 g/L). The results show that larval motility can be a useful parameter to measure in order to determine the sublethal effects of trace metals on coral larvae.     

Toxicity of mercury,copper, nickel,lead, and cobalt to embryos and larvae of zebrafish,Brachydanio rerio

The toxicity of mercury (HgCl₂), copper (CuCl₂: 5 H₂O), nickel (NiSO₄: 6 H₂O), lead (Pb(CH₃COO)₂: 3 H₂O) and cobalt (CoCl₂: 6 H₂O) was studied under standardized conditions in embryos and larvae of the zebrafish,Brachydanio rerio. Exposures were started at the blastula stage (2–4 h after spawning) and the effects on hatching and survival were monitored daily for 16 days. Copper and nickel were more specific inhibitors of hatching than cobalt, lead, and mercury. Nominal no effect concentrations determined from the dose-response relationships (ZEPs, Zero Equivalent Points) for effect on hatching time were 0.05 g Cu/L, 10 g Hg/L, 20 g Pb/L, 40 g Ni/L and 3,840 g Co/L, and those for effect on survival time were 0.25 g Cu/L, 1.2 g Hg/L, 30 g Pb/L, 80 g Ni/L, and 60 g Co/L. The no effect concentrations for Ni, Hg and Pb are consistent with previously reported MATC values for sensitive species of fish. The no effect concentrations for copper are 1–2 orders of magnitude lower than previously reported values. The major reason for the latter discrepancy was considered to be the absence of organics that can complex copper ions in the reconstituted water that we used, which had a hardness of 100 mg/L (as CaCO₃) and a pH of 7.5–7.7. Unexposed controls were started with embryos from different parental zebrafishes and the parental-caused variability in early embryo mortality, median hatching time and median survival time were estimated.     

Measurement of manganese amelioration of cadmium toxicity inChlorella pyrenoidosa using turbidostat culture

Cadmium (Cd) toxicity and amelioration of Cd toxicity by Mn were measured inChlorella pyrenoidosa, using turbidostat culture. The responses were measured in terms of the maximum specific growth rate, _max, of the populations. In turbidostat culture _max is a dependent variable that can be measured continuously. Cd (as CdCl₂· 2.5 H₂O) was added to control populations at a concentration of 1.8 M Cd. Toxicity was expressed after a 5 generation lag and resulted in a _max steady state 62% lower than the initial control after 2 generations. With continued Cd exposure, Mn (as MnCl₂ · 6H₂O) was then added stepwise to a concentration of 10.4 M Mn which caused a rapid, immediate increase in _max followed by linear increase until a steady-state plateau was reached at a _max 90% of control. The ameliorative response spanned 20 culture generations. After addition of Mn (10.4 M), cellular Cd concentration did not change and cellular Mn concentration increased. Increase in mean cell size accompanied Cd exposure and was significantly decreased when supplemented with 10.4 M Mn. Possible mechanisms of the amelioration are discussed.     

The influence of contaminant and water quality conditions on larval striped bass in the Potomac River and upper Chesapeake Bay in 1990: Anin situ study

In situ contaminant and water quality studies were conducted with striped bass prolarvae,Morone saxatilis, in two major spawning areas of the Chesapeake Bay in 1990 to explore the possible effects of water quality and contaminants conditions on survival. Three 96-hin situ survival studies with striped bass prolarvae were conducted at three stations in the Potomac River and three stations in the upper Chesapeake Bay during a major portion of the spawning season (13–20°C). Water quality parameters, inorganic contaminants and organic contaminants were monitored in the water column at these three stations during the experiments. Concentrations of 10 metals associated with precipitation events occurring at field sites on the Potomac River and upper Chesapeake Bay were also determined.Survival of prolarvae ranged from 2 to 17.5% in all three 96-h tests conducted in the Potomac River. Control survival was greater than 79%. Survival of prolarvae during experiment 3 (all stations combined for each experiment) was significantly lower than survival of prolarvae during experiment 1. The low survival of prolarvae during experiment 3 occurred concurrently with a reported fish kill on the Potomac River. Chromium (14 g/L) and zinc (119 g/L) concentrations exceeding U.S. EPA water quality criteria were reported from a 48-h composite sample taken during experiment 3. Lower than normal pH conditions (6.8 and 6.9) were also documented during this experiment. Arsenic, chromium, and zinc may have been stressful.Survival of prolarvae at the three stations during upper Chesapeake Bay tests ranged from 36 to 52.5% for 96-h exposures but was slightly lower (23–34.5%) during a 120-h exposure. Control survival was >81% in all experiments. Survival of prolarvae during all experiments in the upper Bay was similar to natural survival that occurs with this life stage. Adverse water quality and contaminant conditions were not reported in the upper Chesapeake Bay striped bass spawning area.Detectable concentrations of cadmium (0.80 and 0.89 g/L), aluminum (5.4 g/L), chromium (1.1 g/L), and zinc (2.5 g/L) were reported in acidic precipitation samples (pH 3.4) collected from the Potomac River site. Surface water concentrations of these metals did not increase in the Potomac River study area after the precipitation events. The following metals were detected in acidic precipitation (pH 4.06–5.12) in the upper Chesapeake Bay: 22.1 g/L Al; 1.1, 1.8, 2.3 g/L Cd; 1.2 g/L Cu; 2.7 and 3.1 g/L Pb and 4.6 g/L Zn. Concentrations of Al (22.1 g/L) and Pb (3.1 g/L) in precipitation corresponded with increased concentrations in the surface waters at a nearby station in the upper Chesapeake Bay study area.     

Chronic toxicity and bioaccumulation of 2,5,2′,5′- and 3,4,3′,4′-tetrachlorobiphenyl and Aroclor® 1242 in the amphipodHyalella azteca

The addition of 100 (g/L of Aroclor^® 1242 (A1242) or 2,5,2,5-tetrachlorobiphenyl (TeCB) during 10 week chronic toxicity tests withHyalella azteca resulted in complete mortality. There were no effects on survival, growth, or reproduction after addition of 30 g/L. Toxic effects were observed at tissue levels of between 30 and 180 g/g on a wet weight basis, and tissue levels appear to be a better indicator of toxicity than levels in water. No toxic effects were observed after additions of up to 2,700 g/L of the coplanar congener 3,4,3,4-TeCB.H. azteca has the ability to avoid accumulating in excess of 140 g/g 3,4,3,4-TeCB. The amount taken up was proportional to the amount added in water up to 100 g/L, but was constant at higher additions, possibly accounting for its relatively low toxicity. The low toxicity of the coplanar congener, as compared to the non-coplanar 2,5,2,5-TeCB, is in direct contrast to the high toxicity of coplanar PCB congeners to mammals and may be associated with slower rates of aromatic hydrocarbon metabolism in amphipods. Polychlorinated biphenyl levels measured in amphipods from Lake Ontario are approximately 100-fold below levels associated with toxicity inH. azteca, but are above levels which, through biomagnification up the food chain, lead to salmonid residues in excess of 2 g/g, a tolerance limit for human consumption.     

Bioaccumulation and toxicity of selenium in Chironomus decorus larvae fed a diet of seleniferous Selenastrum capricornutum

The bioaccumulation and toxicity of selenium in a simple aquatic food chain was investigated by feeding a diet of seleniferous algae (Selenastrum capricornutum) to fourth instar midge (Chironomus decorus) larvae. Treatment diets consisted of S. capricornutum cultured in three concentrations of selenite (0, 10, and 40 g Se/L) and four concentrations of selenate (0, 4, 10, and 40 g Se/L). The seleniferous algae was freeze-dried and utilized as a diet for the midge larvae. The data show that, under laboratory conditions, a 96 h dietary exposure of 2.11 g Se/g dry weight significantly reduced larval growth at tissue concentrations 2.55 g Se/g dry weight. The results demonstrate that some invertebrates are very sensitive to dietary selenium exposure. When compared to similar studies with Daphnia magna, the data suggest that invertebrate primary consumers differ in the metabolism of dietary selenium.     

Toxicity of microencapsulated permethrin to selected nontarget aquatic invertebrates

Microencapsulated permethrin (penncapthrin) was evaluated under laboratory conditions for its toxicity toward several nontarget aquatic invertebrates. Average LC50 estimates for selected lotic invertebrates, based on a one hour dosing regime, were: 2.71 mg/L forSimulium vittatum, 4.59 mg/L forHydropsyche spp., and 13.41 mg/L forIsonychia bicolor. In acute static tests withDaphnia magna, there was no significant difference (p0.05) between the toxicity of penncapthrin at 96 h (LC50 range: 6.80–22.5 g/L) and the EC formulation at 72 h (LC50 range: 0.6–21 g/L). Comparatively, the toxicity of microencapsulated methyl parathion (penncap-m) was not significantly different from that of penncapthrin towardD. magna, the former having LC50 estimates ranging form 0.3–12.25 g/L. LC50 estimates associated withDaphnia pulex ranged from 19 to 131 g/L. The toxicity of penncapthrin and penncap-m towardD. pulex was difficult to determine because of frequent control mortality due to food deprivation resulting from the need to run tests for longer than 48 h. In successful tests, LC50 estimates ranged from 19 to 28 g/L for penncapthrin and 0.08 to 25 g/L for penncap-m after 72 h exposure. In long term toxicity tests, 95% of D. magna at 1 g/L, 44% at 10 g/L, and 20% at 15 g/L survived after 39 days exposure. Less than 15% ofD. pulex survived over the same concentration range following 32 days exposure. Despite some drawbacks, long-term toxicity tests were more appropriate than short-term tests for evaluating microencapsulated sticides because of reduced variability in LC50 estimates and lower control mortality.     

Influence of cadmium pre-exposure on the preference-avoidance responses of lake whitefish (Coregonus clupeaformis) to cadmium

The preference-avoidance responses of lake whitefish (Coregonus clupeaformis) to Cd were measured following 3 weeks exposure to water containing 0, 0.2, 1, or 5 g Cd/L. Fish movements were tracked in a countercurrent-type trough with clean water on one side, and water containing sequentially increasing Cd concentrations (0–25 g/L) on the other. While fish not previously exposed to Cd showed a weak attraction to the highest test concentration only, those pre-exposed to 5 and 1 g/L Cd were subsequently attracted to water containing Cd at the same concentration to which they had been previously exposed. This response was most pronounced among fish pre-exposed to 5 g/L, which displayed a relatively strong attraction to water containing 5 g/L when compared to responses to other test concentrations. This suggests that Cd imparts an odor or flavor which previously exposed whitefish will seek out. The possible implications of such attraction responses in field situations are discussed.     

Chronic toxicity of the bromoxynil formulation Buctril® to Daphnia magna exposed continuously and intermittently

Two chronic toxicity tests were conducted in which Daphnia magna were either continuously or intermittently exposed to bromoxynil octanoate (BO; as Buctril^®) for 28 d. In the intermittent exposure test, daphnids were exposed to daily pulses of BO with 24-h mean concentrations equal to those in the continuous exposure test, and the peak concentrations were three times the 24-h mean values. After 28 d of continuous exposure to BO, survival of daphnids was reduced at 80 g/L, whereas mean number of young per adult, intrinsic rate of natural increase, and mean weight of adults were all reduced at 40 g/L. Intermittent exposures to daily pulses of BO for 28 d caused reduced survival of daphnids at 24-h mean concentrations 40 g/L and reduced mean number of young per adult, intrinsic rate of natural increase, and mean weight of adults at 24-h mean concentrations 20 g/L. The estimated geometric mean-maximum acceptable toxicant concentrations of BO based on 24-h mean nominal values were 28 g/L for continuous exposures and 14 g/L for intermittent exposures. These results demonstrated that continuous-exposure studies may not be adequate in assessing herbicide toxicity to aquatic biota when concentrations fluctuate temporally.     

The disposition of cadmium and zinc inPandalus montagui

Cadmium uptake rates in various tissues ofPandalus montagui exposed to sea water containing 37 gCd/L for 14 days ranged from 0.002–0.06 g/g dry tissue/hr. During depuration for 57 days, the levels in most tissues decreased slightly, but continued to rise in the hepatopancreas indicating Cd redistribution. Exposure to 65 g Zn/L produced no substantial change in Zn content of the tissues. An increase occurred in eggs and hepatopancreas during the first six days of depuration. During exposure to Cd and Zn combined (40 g Cd/L + 70 g Zn/L), tissue Zn levels responded as with Zn alone. In the presence of Zn, Cd concentration was doubled in the hepatopancreas, depressed by one-third in the carcass, and did not change in the other tissues. Increased amounts of Zn (up to 410 g Zn/L) had no effect on the Cd levels of the tissues except that the Cd level in the hepatopancreas was depressed, although the level was still greater than in the case of exposure to Cd alone. The possible role of metallothionein is discussed.     

A pilot study of lead and cadmium exposure in young children in Stockholm,Sweden: Methodological considerations using capillary blood microsampling

A capillary blood microsampling technique was tested among urban young children in Stockholm. Blood lead (BPb) and hemoglobin (Hb) concentrations were determined in capillary blood obtained by fingerstick from 41 children, 13–20 months old, and the accompanying parent. The quality control included control for lead (Pb) and cadmium (Cd) contamination of material and equipment used for blood sampling, washing procedures for the hands and fingers to be punctured, comparisons of Pb and Cd concentrations in blood obtained by fingerstick and by brachial vein puncture from the same individuals, analysis of external quality control samples for Pb and Cd in blood together with the collected samples, and evaluation of the analytical performance using linear regression analysis.The results showed that blood sampling material may contaminate the blood samples with amounts of Pb and Cd that would seriously influence the monitoring results in the low concentration range (<100 g Pb/L and <1 g Cd/L). However, it is possible to obtain reliable BPb concentrations (>10 g Pb/L), but not BCd concentrations (<1 g Cd/L), with the capillary blood microsampling technique tested provided that a strict quality control is applied. The sampling procedure tested was well accepted by the children and their parents. The children's median BPb concentration (27 g/L; range 9–73 g/L) was similar to the median BPb concentration of their parents (27 g/L; range 7–74 g/L). However, the correlation between child and parent BPb concentrations was poor (R²=0.20), which may indicate different sources to Pb exposure in children and parents.     

Acute and chronic toxicities of arsenic(III) to fathead minnows,flagfish, daphnids,and an amphipod

Acute and chronic toxicities of arsenic (III) (As) to four species of freshwater organisms were determined. All tests were flow-through exposures except the daphnid (Daphnia magna) tests which were static concentration renewal exposures. Acute exposures of fathead minnows (Pimephales promelas), flagfish (Jordanella floridae), and an amphipod (Gammarus pseudolimnaeus) to As resulted in 96-hr LC₅₀ or EC₅₀ estimates of 14,100, 14,400, and 874 g/L, respectively. Daphnids were exposed to As with and without food resulting in 96-hr EC₅₀ estimates of 4,340 and 1,500 g/L, respectively. Chronic exposures of 28 to 31 days duration were made for fathead minnows, flagfish, and daphnids. The chronic limit ranges (highest tested exposure concentration having no adverse effect and the lowest tested exposure concentration having an adverse effect) based upon the most sensitive measured parameters of body length and wet weight were 2,130 to 4,300 g/L for fathead minnows and 2,130 to 4,120 g/L for flagfish. Daphnids had chronic limits of 633 to 1,320 g/L based upon survival and the measured parameters of reproduction and body length. Calculation of an acute test/chronic test ratio for fathead minnows, flagfish, and daphnids (fed and unfed) resulted in a range of values from 1.64 to 4.80.     

The effects of poly chlorinated biphenyls and methylmercury,singly and in combination on mink. II: Reproduction and kit development

Adult ranch-bred mink (Mustela vison) were fed diets containing either 0, 1.0 g/g polychlorinated biphenyls (PCB) (Aroclor^® 1254), 1.0 g/g methylmercury (MeHg), a combination of 1.0 g/g PCB plus 1.0 g/g MeHg, or 0.5 g/g PCB plus 0.5 g/g MeHg. Fertility of adult male mink, percentage of females whelped or number of kits born per female were not affected by the treatments. However, growth rate of kits nursed by mothers exposed to 1.0 g/g PCB was significantly reduced. There was a synergistic effect of PCB and MeHg which reduced kit survival in groups receiving both chemicals simultaneously. Kit survival to weaning in the control, 0.5 g/g PCB/MeHg, and 1.0 g/g PCB/MeHg groups was 72.0%, 62.7% and 35.8%, respectively. The results suggest that growth and survival of mink kits are adversely affected at dietary levels of PCB and MeHg currently present in some environments.     

Biological and environmental monitoring of occupational exposure of pharmaceutical plant workers to methotrexate

Summary The exposure of 11 pharmaceutical plant workers to methotrexate (MTX) was studied. Personal air samples were taken during the different manufacturing processes: drug compounding, vial filling, and tablet preparation. The uptake of MTX was established by the determination of MTX in urine. MTX was analyzed using the fluorescence polarization immunoassay (FPIA), a method that is frequently used for monitoring serum levels in patients treated with MTX. The FPIA method was modified in such a way that MTX could be measured quickly and efficiently in air and urine samples. MTX was detected in air samples of all workers except for those involved in the vial filling process (range: 0.8–182 g/m³; median: 10 g/m³). The highest concentrations were observed for workers weighing MTX (118 and 182 g/m³). MTX was detected in urine samples of all workers. The mean cumulative MTX excretion over 72–96 h was 13.4 g MTX-equivalents (range: 6.1–24 g MTX-equiva g MTX-equivalents (range: 6.1–24 g MTX-equivalents). lents). A significantly lower background level of 10.2 g A significantly lower background level of 10.2 g MTX-equivalents was measured in urine of 30 control persons (range: 4.9–21 g MTX-equivalents).     

Lead,cadmium, and aluminum accumulation in the red swamp crayfishProcambarus clarkii G. collected from roadside drainage ditches in louisiana

The concentration of Pb, Cd, and Al in tissues of crayfishProcambarus clarkii were evaluated from several wetland sites located adjacent to roadways and were compared to crayfish harvested from a commercial site free from roadside influences. Abdominal muscle, hepatopancreas, alimentary tract, exoskeleton and blood were analyzed for metal content. Results indicated that levels of contamination obtained in almost all tissues of crayfish from roadside ditches contained significantly higher amounts of metals than those of the commercially harvested control crayfish (p = .05–.001). Detection limits of Pb, Cd, and Al ranged from 0.04 g Pb/g to 16.15 g Pb/g.001 g Cd/g to .13 g Cd/g, and 1.22 g Al/g to 981 g Al/g, respectively. Concentrations of Pb, Cd, and Al were highest in the hepatopancreas and alimentary tract. High levels of these elements were also detected in the exoskeleton. In contrast, muscle tissue was the least affected tissue. Several significant correlations among concentrations of metals were found when comparing a variety of tissues inProcambarus clarkii.     

Toxicity of aldicarb and fonofos to the early-life-stage of the fathead minnow

Flow-through early-life-stage (ELS) toxicity tests were conducted with the pesticides aldicarb (Temik^®) and fonofos (Dyfonate^®) to determine their effect on the survival and growth of fathead minnows. Concentrations of 78g/L of aldicarb and 16g/L of fonofos did not affect survival and growth. However, 156g/L of aldicarb and 33g/L of fonofos were lethal to larval-juvenile exposed for 30 days post-hatch. The maximum acceptable toxicant concentration (MATC) of aldicarb and fonofos for the fathead minnow is estimated to be between 78–156g/L and 16–33g/L, respectively. The corresponding chronic values (geometric mean of MATC values) would be 110g/L and 23g/L. Acute toxicity tests gave 96-hr LC50 values of 1370g aldicarb/L and 1090g fonofos/L. The acute-chronic ratio (96-hr LC50/chronic value) is 12 for aldicarb and 47 for fonofos.     

Biological effects of Kepone and mirex in freshwater invertebrates

Acute and chronic toxicity studies of Kepone^® (chlordecone) and mirex were conducted with daphnids (Daphnia magna), amphipods (Gammarus pseudolimnaeus), and larvae of a midge (Chironomus plumosus). Acute toxicities of Kepone ranged from a 48-hr EC50 of 350g/L for midges to a 96-hr LC50 of 180g/L for amphipods, whereas the acute toxicities of mirex to all three taxa exceeded 1000g/L. Maximum acceptable toxicant concentrations (MATC's) for Kepone and mirex were estimated by measuring reproduction of daphnids, growth of amphipods, emergence of midges, and survival of all organisms. MATC for Kepone was estimated to be between 9 and 18g/L for daphnids, between 1 and 2g/L for amphipods, and between 8.4 and 18g/L for midges; MATC for mirex exceeded 34g/L for daphnids and midges, but less than 2.4g/L for amphipods. The concentration of Kepone and mirex accumulated by daphnids was 760 and 8025 times, respectively, the concentration in water. Estimated times for elimination of 50% of the residues by daphnids were 141 hr for Kepone and 12 hr for mirex.     

Nitrous oxide in blood and urine of operating theatre personnel and the general population

Nitrous oxide (N₂O) was assayed in 676 urine samples and 101 blood samples provided after exposure by operating theatre personnel from nine hospitals. The blood and urine assays were repeated in 25 subjects 18 h after the end of exposure. For 80 subjects, environmental N₂O was also measured during intraoperative exposure. Mean urinary N₂O in the 676 subjects at the end of exposure was 40 g/l (range 1–3805 g/l); in 10 of the 676 subjects, urinary N₂O was in the range 279–3805 g/l (mean 1202 /l). The 98^th percentile was 120 g/l. Mean blood N₂O at the end of exposure, measured in 101 subjects, was 21 g/l (median 16 g/l, range 1–75 g/l). Blood and urine N₂O (1.5 g/l and 4.9 g/l, respectively) in 25 subjects, 18 h after exposure, was significantly higher than in occupationally non-exposed subjects (blood 0.91 g/l, urine 1 g/l). Environmental exposure was significantly related to blood and urinary N₂O (r = 0.59 andr = 0.64, respectively). Blood and urinary N₂O were significantly related to each other (r = 0.71), and were equivalent to about 25% of the environmental exposure level. The mean urinary N₂O of 1202 g/l in 10/676 subjects was not related to environmental exposure in the operating theatre. The highest urinary N₂O levels measured in these 10/676 subjects could be explained by an asymptomatic urinary infection.