Occupational chronic exposure to metals

Summary External and internal chromate exposure of 103 stainless steel welders who were using manual metal arc welding (MMA), metal inert gas welding (MIG) and both methods, were measured by ambient and biological monitoring. At the working places the maximum chromium trioxide concentrations were 80 g/m³. The median values were 4 g/m³ (MMA) and 10 g/m³ (MIG). The median chromium concentrations in erythrocytes, plasma and urine of all welders were < 0.60, 9.00 and 32.50 g/l. For biological monitoring purposes, chromium levels in erythrocytes and simultaneously in plasma seem to be suitable parameters. According to our results, chromium levels in plasma and urine in the order of 10 and 40 g/l seem to correspond to an external exposure of 100 g chromium trioxide per cubic metre, the technical guiding concentration (TRK-value). Chromium concentrations in erythrocytes greater than 0.60 g/l indicate an external chromate exposure greater than the TRK-value.     

Mercury vapor as an atmospheric contaminant of dental offices

Airborne mercury from dental offices was selectively trapped by silver gauze elements in borosilicate glass absorbers, followed by heat-desorption and spectrophotometric measurement at 2537A. As little as 0.4 ng of Hg could be accurately determined, which is equivalent to 49 ppt in a one-L air sample on a v/v basis. Over 860 air samples were taken over a range of locations and working conditions at 88 different dental offices, and at the Dental Training Clinic of the University of Manitoba. The Hg vapor concentrations at the dental facilities ranged from 0.45 to 742g/m³ of air; 29% of the samples were within 0.45 to 5g; 37.8 were within 5.1 to 25g; and 33.2% were above 25g. Mercury concentrations varied during the working day, depending on the time of sampling, the number of amalgams placed, and the interval between placements. The lowest concentrations were obtained in the morning. Disturbance of residual mercury droplets on floors or working areas by sweeping or dusting, or immediately after attempted clean-up of a mercury spill, sharply increased the amount of airborne mercury.     

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.     

Sister chromatid exchange and chromosomal breakage in pentachlorophenol (PCP) exposed workers

Summary A cytogenetic study was performed on 20 healthy workers exposed to pentachlorophenol (PCP) in concentrations ranging from 1.2 to 180 g/m³ (Maximum Concentration at the workplace is 500 g/m³) for 3 to 34 years. PCP was determined in the blood plasma of all probands, yielding concentrations between 23 and 775 g/l (Biological Tolerance Value is 1000 g/1). In vitro PCP up to 90 mg/l was added to phytohaemagglutinin stimulated lymphocytes of normal healthy donors without any effect on sister chromatid exchange (SCE) or chromosomal aberrations (CA), whereas a slowdown of cell proliferation could be detected in the presence of 60 mg PCP/l. In vivo we neither observed a relation between PCP concentrations and the number of SCE nor an increase of CA.     

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.     

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).     

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.     

Mercury and methylmercury in population risk groups on the Atlantic coast of Southern Spain

The presence of methylmercury and total mercury in the hair of high risk groups residing in the highly industralized South Atlantic coastal area of Spain were studied. In fishermen, total mercury and methylmercury content showed slight non-statistically significant differences among groups from two different coastal areas (geometric means: 10.41 and 8.36 g/g for total mercury; 8.28 and 6.72 g/g methylmercury). Mercury content in both groups differed significantly from controls (geometric mean 2.5 g/g total mercury, 4.50 g/g for methylmercury; p<0.05). In pregnant women, statistically significant differences were found in the three groups (two coastal areas and controls). Geometric means were 2.40, 5.94, and 0.94 g/g for total mercury and 1.93, 4.78, and 0.82 g/g for methylmercury. Results were compared with those obtained in other European countries in the Mediterranean area. Simultaneously, the same compounds were analyzed in fish and molluscs from those most consumed by people in the above-mentioned groups. The following results were obtained: sword fish, 1.57±1.27 g/g and 1.20±0.94 g/g for total mercury and methylmercury respectively; Scrobicularia plana, 0.07±0.052 and 0.053±0.039 g/g; Tapes decussatus, 0.046±0.20 and 0.039±0.018 g/g.     

Effects of mercury,selenium, and organochlorine contaminants on reproduction of Forster's terns and black skimmers nesting in a contaminated Texas Bay

Mean mercury (0.40 g/g), and geometric mean DDE (1.6 g/g) and polychlorinated biphenyl (PCB) (2.3 g/g) concentrations in Forster's tern (Sterna forsteri) eggs from Lavaca Bay were higher than those in tern eggs from a reference area in San Antonio Bay, but residues were not correlated with hatching success. Nest success was similar between bays. Selenium levels in Lavaca Bay tern eggs (0.71 g/g) were also comparable to those in eggs from the reference area (0.68 g/g).Clutch size (3.1 to 3.4) of Lavaca Bay black skimmers (Rynchops niger) was no different than that (3.4) at a reference colony near Laguna Vista. Nest success was similar among three Lavaca Bay colonies, but success was lower at one Lavaca Bay colony (40%) than at Laguna Vista (65%). Mean mercury (0.46 g/g) and selenium (0.75 g/g) concentrations in skimmer eggs from Lavaca Bay were higher than those (0.19, 0.33 g/g) from Laguna Vista; however, concentrations of neither contaminant were related to hatching success. DDE concentrations in Lavaca Bay skimmer eggs (3.4 g/g) were similar to those from Laguna Vista (3.2 g/g) and DDE was negatively correlated with hatching success. PCBs were higher in eggs from Lavaca Bay (1.3 g/g) than Laguna Vista (0.8 g/g). Organochlorine and metal contaminants in most eggs were below embryotoxic levels. Eggshell thinning in Forster's terns (7%) and black skimmers (5%) was below that associated with lowered reproduction.DDE and PCBs were detected in 9 Caspian tern (S. caspia) eggs; maximum concentrations were 4.7 and 5.4 g/g. Caspian tern and least tern (S. albifrons) eggs contained low (0.9 g/g) concentrations of mercury and selenium.     

An evaluation of the significance of mouth and hand contamination for lead absorption in lead-acid battery workers

Summary The present study was conducted to evaluate the role of ingestion through hand and mouth contamination in the absorption of lead in 25 lead-acid battery workers. Levels of personal exposure to airborne lead ranged from 0.004 to 2.58 mg/m³ [geometric mean 0.098, with 25% of samples exceeding threshold limit values (ACGIH) of 0.15 mg/m³]; the mean (SD) blood lead level was 48.9 (10.8) g/dl. Mean hand lead contents increased 33-fold from preshift levels on Monday mornings (33.5 g/500 ml) to midshift levels on Thursday afternoons (1121 g/500 ml). Mouth lead contents increased 16-fold from 0.021 g/50 ml on Mondays to 0.345 g/50 ml on Thursdays. The typical Malay racial habit of feeding with bare hands and fingers without utensils (closely associated with mouth and hand lead levels on Mondays) explained the bulk of the variance in blood lead levels (40%), with mouth lead on Thursdays (closely associated with poor personal hygiene) explaining a further 10%. Air lead was not a significant explanatory variable. The implementation of a programme of reinforcing handwashing and mouth-rinsing practices resulted in a reduction of the blood lead level by 11.5% 6 months later. These results indicate that parenteral intake from hand and mouth contamination is an important cause of lead absorption in lead-exposed workers.     

Lead exposure in indoor firing ranges

Summary Higher air lead levels (time-weighted average 660, range 112–2238 g/m³) were measured in firing ranges where powder charges were employed than in ranges where air guns were used (4.6, range 1.8–7.2 g/m³); levels in the latter were in turn higher than those in ranges used for archery (0.11, range 0.10–0.13 g/m³) Twenty-two marksmen who used powder charges had significantly increased blood lead levels during the indoor shooting season (before: median 106, range 32–176 g/l; after: 138; range 69–288 g/l; P = 0.0001), while 21 subjects who mainly used air guns displayed no significant increase (before: median 91, range 47–179 g/l; after: 84; range 20–222 g/l). Thirteen archers had significantly lower levels than the pistol shooters before the season (P = 0.006), and showed a significant decrease during the season (before: median 61, range 27–92 g/l; after: 56; range 31–87 g/l; P = 0.04). At the end of the indoor season, there was a significant association between weekly pistol shooting time and blood lead levels.     

Cadmium and mercury in sediment and burrowing mayfly nymphs (Hexagenia) in the upper Mississippi River,USA

Longitudinal patterns in the cadmium and mercury content of burrowing mayflies (Hexagenia) and surrounding sediments were examined along a 572-km reach of the upper Mississippi River. Surficial sediments and Hexagenia nymphs were sampled in 1989 at 12 sites extending from Pool 2 through Pool 16 and analyzed for total recoverable cadmium and total mercury. In sediment and nymphs, concentrations of both metals were highest in Pools 2, 3, and 4, which are just downstream from the Twin Cities (Minneapolis-St. Paul, Minnesota) metropolitan area, the primary anthropogenic source of metals to the studied reach of river. Concentrations of the two metals in sediments indicated a significant anthropogenic contribution, which was most pronounced for cadmium. The cadmium concentrations in surficial sediment varied less than 3-fold (range, 1.19–3.23 g/g dry weight) among the 12 sites, whereas concentrations in Hexagenia varied almost 20-fold (range, 0.13–2.35 g/g dry weight). Nymphs from Pools 2–4 had much greater concentrations of cadmium than nymphs from sites further downstream, even though the mean concentration of cadmium in sediment from Pools 2–4 (3.0 g/g) was just twice that (1.6 g/g) for the nine sites downstream. Mercury in sediments from the 12 sites ranged from 0.038 to 0.165 g/g dry weight, averaging 0.14 g/g in Pools 2–4 and 0.056 g/g in the nine sites downstream. In nymphs, mercury concentrations ranged from 0.041 to 0.134 g/g dry weight. The bioavailability of sediment-associated cadmium seemed greater in Pools 2, 3, and 4 than in the sites further downstream, based on the relative cadmium concentrations in Hexagenia nymphs and sediment. Moreover, it is concluded that the trapping of sediment and associated metals in Lake Pepin (a natural riverine lake in Pool 4) significantly reduces the exposure of the ecosystem further downstream to metals from the Twin Cities and other upstream anthropogenic sources.Journal Paper No. J15705 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA. Project No. 2627     

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.     

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.     

Monitoring lead pollution near a storage battery recycling plant in Taiwan, Republic of China

This study presents the distribution of blood lead levels and lead in various environmental samples (water, sediments, soils, and air) near the Shing-Yie storage battery recycling plant in Taiwan before (July 1990 to June 1991) and after (July 1992 to June 1993) amelioration. Before amelioration, the average blood lead levels in the neighborhood of the plant were in the range of 10.55±5.7 to 12.28±7.9 g/dl. After amelioration, relatively lower average concentrations of blood lead (range 8.35±3.0 to 9.13±2.5 g/dl) were generally found; however, these averages were still higher than that (7.79±3.5 g/dl) from other lead-unpolluted areas of Taiwan. An exceedingly high geometric mean (GM) lead concentration (128 g/L) was found in the downstream river water of the Tawulum River passing by the plant. The concentrations of lead (GM=372 and 418 g/g) in the downstream river sediments were higher than those (GM=123 and 158 g/g) in the upstream river sediments before and after amelioration, respectively. Furthermore, lead species in river sediments were analyzed by a sequential leaching technique. The sum of phases I, II, and III accounted for 83.7% of total lead at station R₂ (nearest to the plant). Maximum lead concentration (GM=2402 g/g) in dust at the soil surface from station S₁ (nearest to the plant) was much higher than those from the other stations by about 18 times before amelioration. However, the maximum value dropped to 1,155 g/g after amelioration. On the whole, the geometric mean concentration of lead in dust at the soil surface nearest to the plant was >1,000 g/g and decreased to <100 g/g in the 15–30 cm depth soil about 2 km away from the plant. Before amelioration, the geometric mean lead concentration of 4.57 g/m³ (range 0.102–37.6 g/m³) in the air near the plant was higher than that at the background locations, the geometric mean value of which was 0.08 g/m³.     

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.     

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.     

Increase in the amount of erythrocyte δ-aminolevulinic acid dehydratase in workers with moderate lead exposure

Summary The amount of ALA-D in human erythrocytes was determined directly by radioimmunoassay or calculated from the restored activity assayed in the presence of zinc and dithiothreitol, and a good correlation was observed between the RIA-based and the restored activity-based amounts.The RIA-based amount of ALA-D in the blood of 10 normal individuals (blood lead levels of 5.6 ± 2.3 g/100 ml: mean ± SD) and 19 lead-exposed workers (blood lead levels of 41.2 ± 10.2 g/100 ml) was 54.1 ± 11.8 g/ml blood and 92.3 ± 20.6 g/ml blood, respectively, indicating an apparent increase of the enzyme amount in lead-exposed workers.A significant increase in the amount of erythrocyte ALA-D calculated from the restored activity in lead-exposed workers was observed even in the low blood lead level of 10–20 g/100 ml, resulting in the range of blood lead level 20–40 g/100 ml. No significant difference was observed in hematocrit and hemoglobin content between lead-exposed and non-exposed groups. These observations suggested that the increase of erythrocyte ALA-D in lead exposure was not due to anemia, which might result in the increase of young erythrocytes in peripheral blood.This increase in the amount of ALA-D in human erythrocytes might be a result of the function to overcome the inhibition of the enzyme in bone marrow cells during lead exposure, and these findings may throw light on the danger to human health of low-level lead toxicity.Abbreviations ALA-D -Aminolevulinic acid dehydratase or 5-Amnoevulinic acid hydro-lyase, EC 4.2.1.24 - ALA -Aminolevulinic acid - Rc Reticulocyte - RIA Radioimmunoassay - DTT Dithiothreitol Supported in parts by Science Research Fund of the Ministry of Education, Science and Culture of Japan and by Research Grant of Fujiwara Foundation of Kyoto University     

Occupational exposure and drift hazard during aerial application of paraquat to cotton

Two worker-exposure and drift trials were conducted during the aerial application of paraquat to cotton in California, USA. The dermal and respiratory exposure of pilots, flaggers, and a mixer-loader was shown to be low. Dermal exposure ranged from 0.05 (pilot) to 2.39 (flagger) mg/ hr. The dermal exposure of the mixer-loader was similar to that of the pilots. No respirable paraquat was detected in the breathing zone of any worker. The highest total paraquat concentration was 26.3 g/m³ for a flagger, which is a factor of 19 less than the TLV for total paraquat. The combined dermal and respiratory exposure of this flagger was equivalent to 19.4 mg/8hr working day. Paraquat drift concentrations decreased with increasing distance downwind of the spray application. The highest concentrations of total and respirable paraquat were 16.7 and 0.15 g/m³ at 50 m from the application site perimeter. The respective concentrations at 1600 m downwind were 0.5 and 0.01 g/m³. Measurement of the particle size distribution of paraquat drift showed that 0.95 to 1.96% of spray droplets was within the respirable range at all distances downwind. The highest percentage of respirable droplets was equivalent to 1.2 (g paraquat, which was measured at 400 m downwind. Respirable fractions of 1 and 0.95% were measured at 50 and 100 m downwind, which represented 1.8 g paraquat. There was no evidence, therefore, of a toxic hazard to pilots, ground crew, and downwind bystanders, as a consequence of the aerial application of paraquat.     

Occupational exposure to hexachlorocyclohexane

Summary In a lindane (-hexachlorocyclohexane =-benzenehexachloride)-producing factory 57 workers were studied with regard to their blood levels of the three hexachlorocyclohexane isomers:-, -, and-HCH. The TLV-TWA (MAK value 1979) for-HCH of 0.5 mg/m³ was not exceeded at any of the workplaces where HCH is synthesized and purified to lindane. Additionally, in some of the workers samples of s.c. adipose tissue were taken for determination of HCH-isomer content. An external group of 20 clerks was examined in the same way for control purposes.In contrast to the control persons, none of whom had HCH-concentrations in serum above the respective detection limits, the values determined in serum of the exposed workers were in the following ranges:-HCH: 10–273 g/l,-HCH: 17–760 g/l, and-HCH: 5-188 g/l. Of special interest is the observation of a significant increase of-HCH-concentration in serum with the time of employment in lindane production, indicating a pronounced accumulation of this substance in the human organism. Concentrations of this isomer in s.c. adipose tissues were about 300-fold higher than in serum. A significant correlation between both parameters could be established.The results of this study show that adherence to the TLV-TWA of-HCH is not sufficient for control of HCH-exposure. Furthermore, biological monitoring of exposed workers is necessary taking into account the three more important isomers-, -, and-HCH.