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Archives of Environmental Contamination and Toxicology (v.36, #4)

Assessment of Toxic Interactions of Heavy Metals in Binary Mixtures: A Statistical Approach by N. H. Ince; N. Dirilgen; I. G. Apikyan; G. Tezcanli; B. Üstün (pp. 365-372).

Toxicity of zinc, copper, cobalt, and chromium ions and their binary interactions were studied at varying test levels by using a battery of two tests, Microtox and duckweed with Vibrio fisheri and Lemna minor as test organisms, respectively. The type of toxic interaction at each test combination was assessed by a statistical approach based on testing the null hypothesis of “additive toxicity” at 95% confidence level. The interactions were called “antagonistic,”“additive,” or “synergistic” in accordance with the statistical significance and the sign of the difference between the tested hypothesis and the value of the observed toxicity at the binary test level concerned. In the majority of the combinations studied by the two bioassays, the interactions were of antagonistic nature. Additive toxicity was the next frequently predicted interaction in both test results, the frequency being much higher in Microtox responses than in those of duckweed. Finally, synergism was found to be a rare interaction in Microtox results, but totally unlikely in duckweed within the selected test combinations.

Acrolein-Induced Toxicity—Defective Mitochondrial Function as a Possible Mechanism by N. Arumugam; J. Thanislass; K. Ragunath; S. Niranjali Devaraj; H. Devaraj (pp. 373-376).

Administration of acrolein (2.5 mg/kg body weight/day) to rats for 45 days depleted the glutathione level in liver, which triggered an imbalance in the antioxidant defense, resulting in lipid peroxidation. Enhanced lipid peroxidation damaged the membranous structure of mitochondria, which was indicated by the loss of lamellae, and increased the oxidation of exogenously added NADH. Loss in membrane integrity altered the activities of the tricarboxylic acid cycle enzymes and levels of cytochromes. Decreased rate of ADP—stimulated oxygen uptake, respiratory coupling ratio, and ATP synthesis—were also observed. We report that the acrolein-induced toxicity is mediated through the depletion of GSH leading to impairment of rat liver mitochondrial function.

PCDD/F Levels in the Vicinity of an Old Municipal Solid Waste Incinerator: Temporal Variation in Soils by J. L. Domingo; M. Schuhmacher; S. Granero; J. M. Llobet; H. A. M. de Kok (pp. 377-383).

In order to determine the temporal variation in the levels of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in soils in the vicinity of an old municipal solid waste incinerator (Montcada, Barcelona, Spain), in 1997 we collected 24 soil samples at the same sampling points in which samples were taken 1 year before. Each sample was analyzed for PCDDs and PCDFs by GC/MS. While in the previous study PCDD/F concentrations ranged from 0.30 to 44.26 ng TEQ/kg (dry matter), (median and mean values: 3.52 and 6.91 ng TEQ/kg), in the present study PCDD/F levels ranged from 0.15 to 29.27 ng TEQ/kg (median and mean values: 2.56 and 4.47 ng TEQ/kg). PCDD/F concentrations decreased in 14 of the 24 soil samples, while the remaining 10 samples showed increases of different orders. No statistically significant differences in PCDD/F levels according to the main wind directions in the area were noted. In both surveys, the highest PCDD/F concentrations were found 750 m from the stack to the south. The current levels of PCDD/Fs in soils, as well as those found in the previous survey are similar or even lower than PCDD/F concentrations reported for soil samples taken near to municipal solid waste incinerators from different places.

Induced Metal Tolerance in Microbenthic Communities from Three Lowland Rivers with Different Metal Loads by V. Lehmann; G. M. J. Tubbing; W. Admiraal (pp. 384-391).

The response of microbenthic communities to sustained metal stress was studied in three lowland rivers with different levels of pollution. Tolerance against zinc and cadmium was determined in short-term toxicity tests with microbenthic assemblages colonizing glass discs. Photosynthetic activity served as an endpoint in tests for algae, whereas for bacteria thymidine incorporation was determined. For bacterial assemblages from unpolluted locations, EC₅₀ values in short-term tests ranged between 6.7 and 56.2 μM zinc, and 8.7 and 25.5 μM cadmium, respectively. Bacterial assemblages from the two most polluted sites were significantly more tolerant for zinc (EC₅₀: 994 μM and >1,000 μM) and cadmium (EC₅₀: 218 μM and 154 μM). Results indicated a shift in community composition toward pollution-adapted organisms when a threshold concentration of 1 μM zinc is exceeded. Although an increasing community tolerance was also indicated for algae, EC₅₀ values for microbenthic algae from all sites exceeded in most cases the highest metal concentrations tested (Zn: 1,000 μM; Cd: 320 μM). Since species composition of algal assemblages was found to change at much lower metal levels, it is concluded that short-term toxicity tests measuring photosynthesis inhibition do not reflect well the long-term effects of these metals. Toxic effects of metals on both algal and bacterial assemblages are attenuated by precipitation and complexing capacities of the biofilm.

Ordination of Zooplankton Community Data to Detect Pesticide Effects in Pond Enclosures by D. P. Kreutzweiser; M. J. Faber (pp. 392-398).

Trends in community structure of crustacean zooplankton among 17 forest pond enclosures (5 m × 5 m × 1 m deep) were examined and analyzed to determine effects of two candidate forest pesticides. Eight enclosures were treated at two concentrations of an experimental insecticide, tebufenozide; five were treated at two concentrations of a biological herbicide, bialaphos; and four served as controls. Zooplankton community structure was characterized by ordination of species assemblages using principle components analysis (PCA) and correspondence analysis (CA). Two-dimensional plots of the first two axes from PCA and CA were constructed to explore temporal and treatment-related patterns in community structure. The first four axes of both ordination functions were used as multivariate descriptors of community structure and were examined for differences among treatments by ANOVA. Species ordination plots and sorted rotated factor loadings provided objective means of identifying the species important in determining divergence in community structure. These were considered indicator species and were examined for differences among treatments by ANOVA and specified contrasts. The ordination and subsequent analysis revealed trends in community structure and sample differences that indicated clear, concentration-dependent effects of bialaphos and equivocal effects of tebufenozide.

Effect of Lindane on the Clearance Rate of Daphnia magna by E. M. Hartgers; E. H. W. Heugens; J. W. Deneer (pp. 399-404).

The impact of the insecticide lindane (γ-hexachlorocyclohexane) on the clearance rate (CR) of Daphnia magna was investigated using artificial beads. CR (24-h EC₅₀: 65 μg L⁻¹) was found to be a more sensitive endpoint than acute lethality for D. magna (48-h LC₅₀: 516 μg L⁻¹). The onset of the effect was rapid; after 2 h of exposure to approximately 241 μg L⁻¹ of lindane a significant decrease in CR was observed. Daphnids recovered rapidly after transfer to clean water; after 24 h of exposure to approximately 250 μg L⁻¹ lindane, transfer into clean water resulted in recovery to 80% of control levels within 2 h and complete recovery within 24 h.

Effects of Heavy Metals (Hg²⁺, Cd²⁺, Pb²⁺) During the Embryonic Development of Acridid Grasshoppers (Insecta, Caelifera) by B. Devkota; G. H. Schmidt (pp. 405-414).

Heavy metals present in the soil get differently accumulated in organisms and show different rates of toxicity at different stages of the life cycle of any organism living there. To see whether such toxicants get accumulated during the embryonic development and/or change the normal developmental processes of organisms exposed to heavy metals, freshly laid eggs and egg pods of two acridids, Aiolopus thalassinus and Eyprepocnemis plorans, were tested against different concentrations of Hg²⁺, Cd²⁺, and Pb²⁺. At increasing Hg²⁺ concentration in the substrate, an increased egg mortality and reduced nymphal hatching in A. thalassinus were observed, yet no change in the normal duration for embryonic development was noticed. A higher hatching rate of E. plorans nymphs than that of A. thalassinus could possibly be due to the higher tolerance, contributed by larger egg volume and thicker foam around the egg pods of the former. Treated concentrations of Hg²⁺ could be of sublethal (0.121 μg Hg²⁺/g substrate) to lethal (0.605 μg and more Hg²⁺/g substrate) doses. The mortality of eggs did not always increase with increasing substrate concentration of Cd²⁺ and Pb²⁺, and the hatching rates of both grasshopper species in many cases were even higher than that in the control. Still, lower accumulation factors of Cd²⁺ and Pb²⁺ than that of Hg²⁺ were found coupled with not increased mortality. The tested concentrations of Cd²⁺ and Pb²⁺ in the substrates, thus, could be of subacute doses. The embryonic development was found prolonged due to Cd²⁺ and Pb²⁺. During parallel egg and egg pod treatments, higher metal concentrations were found in not developed eggs than that in fresh nymphs hatching from the same substrates. This indicated the role of foam around the egg pods as “protective filter” against the toxic substances in the soil.

The Effects of Copper on Blood and Biochemical Parameters of Rainbow Trout (Oncorhynchus mykiss) by G. M. Dethloff; D. Schlenk; S. Khan; H. C. Bailey (pp. 415-423).

Metals are released into aquatic systems from many sources, often at sublethal concentrations. The effects of sublethal concentrations of metals on fish are not entirely understood. The objective of this study was to determine the hematological and biochemical effects of a range of copper concentrations (6.4, 16.0, 26.9 μg Cu/L) on rainbow trout (Oncorhynchus mykiss) over a prolonged period of time. Trout were exposed to copper, and, at intervals of 3, 7, 14, and 21 days, selected parameters were evaluated. Hemoglobin, hematocrit, plasma glucose, and plasma cortisol levels were elevated in trout exposed to 26.9 μg Cu/L at day 3 and then returned to levels comparable to control fish. Plasma protein and lactate levels were not significantly altered in trout from any copper treatment. Hepatic copper concentration and hepatic metallothionein mRNA expression were consistently elevated in trout exposed to 26.9 μg Cu/L. Both of these parameters stabilized by day 3, with only hepatic copper concentration showing a further increase at day 21. Hepatic copper concentration and hepatic metallothionein mRNA expression appear to be robust indicators of copper exposure. Most blood-based parameters evaluated appear to be associated with a transitory, nonspecific stress response. The return of elevated hematological and biochemical parameters to control levels after 3 days and the stabilization of hepatic metallothionein mRNA expression and copper concentration over a similar time period suggested acclimation to dissolved copper at 26.9 μg/L. Further analysis of the data on blood-based parameters indicated that certain parameters (hemoglobin, hematocrit, plasma glucose, plasma cortisol) may be useful in field monitoring.

Residues of Organochlorines in Sediments and Tilapia Collected from Inland Water Systems of Hong Kong by H. Y. Zhou; R. Y. H. Cheung; M. H. Wong (pp. 424-431).

The levels and patterns of organochlorines including DDTs, HCHs, and PCBs were investigated in sediments and tilapia (Tilapia mossambica) collected from inland water systems [Tai Wai (S1), Fo Tan (S2), Siu Lek Yuen (S3), Tai Po (S4), and Tai Wo (S5)] in the New Territories of Hong Kong. Sediment and tilapia samples were also collected from two fish ponds for comparison. The ranges of DDTs, HCHs, and PCBs in river sediments were 2.82–8.63 ng/g (DW), 0.05–2.07 ng/g (DW), and 43–461 ng/g (DW), respectively. All these values were significantly higher (p < 0.05) than the pond sediments. Low chlorinated congeners (especially mono-, tri-, and tetrachlorobiphenyls) were enriched in sediment samples accounting for 70–80% of total PCBs. The ranges of DDTs, HCHs, and PCBs in tilapia muscle collected from Fo Tan and Tai Wai were 28.2–40.1 ng/g (DW), 2.04–3.76 ng/g (DW) and 267–310 ng/g (DW), respectively. These values were also significantly higher (p < 0.05) than those collected from the fish ponds. Higher chlorinated PCBs (tetra-, penta-, hexa-, and heptachlorobiphenyls) were commonly found in tilapia accounting for almost 60% of the total PCBs. The effect of lipid contents in organochlorines accumulation was not significant (p < 0.05) in general.

Polychlorinated Dibenzo-p-Dioxins (PCDDs) and Dibenzofurans (PCDFs) in Muscle and Eggs of Salmonid Fishes from the Great Lakes by J. P. Giesy; K. Kannan; J. A. Kubitz; L. L. Williams; M. J. Zabik (pp. 432-446).

Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were measured in dorsal muscle and eggs of coho salmon, lake trout, and chinook salmon collected from Lakes Superior, Michigan, and Huron (Michigan waters). Absolute and relative concentrations of PCDDs and PCDFs varied among sampling locations (inter- and intralake) and fish species. Fish collected from Bay City (Saginaw Bay) contained the greatest concentrations of PCDDs and PCDFs both in muscle and eggs. Among the three fish species, chinook salmon accumulated greater concentrations than did coho salmon or lake trout. Concentrations of PCDFs were greater than those of PCDDs in all fishes. OCDF and TCDF were the predominant congeners of PCDF, whereas OCDD and TCDD concentrations predominated in PCDDs. Homolog compositions of PCDDs and PCDFs suggested the existence of multiple local sources in various locations. Concentrations of PCDDs and PCDFs in eggs of fishes were significantly correlated with those in muscle.

Serum Concentrations of Various Environmental Contaminants and Their Relationship to Sex Steroid Concentrations and Phallus Size in Juvenile American Alligators by L. J. Guillette Jr.; J. W. Brock; A. A. Rooney; A. R. Woodward (pp. 447-455).

Recent studies have reported a number of abnormalities in the hatchling and juvenile alligators of Lake Apopka, FL (USA). These abnormalities include modifications of plasma concentrations of sex steroids in males and females as well as abnormalities in gonadal morphology, gonadal enzyme activity, and steroidogenesis. Embryonic exposure to environmental contaminants in the eggs has been hypothesized to be the causal agent for these changes. However, posthatchling exposure can also contribute to changes in reproductive and endocrine functioning. We have detected serum concentrations of 16 of 18 organochlorine pesticides or metabolites (OCs) and 23 of 28 congener-specific polychlorinated biphenyls (PCBs) examined in juvenile alligators from Lake Apopka, Orange Lake, and Lake Woodruff National Wildlife Refuge. Lake Apopka juveniles had significantly elevated serum concentrations of p,p′-DDE, dieldrin, endrin, mirex, oxychlordane, ΣDDTs, and ΣPCBs compared to juveniles from the other lakes. Further, we observed no correlations between serum contaminant concentrations and sex steroid concentrations (estradiol-17β and testosterone). However, serum testosterone was significantly lower in males from Lake Apopka and Orange Lake compared to Lake Woodruff NWR. We did not observe relationships between phallus size or other body parameters and serum contaminant levels. Phallus size was smaller in males from Lake Apopka even after adjustment for body size. We suggest that the observations previously reported for juvenile alligators—and observed again in this study—are apparently not associated with the current serum levels of the environmental contaminants we measured, but could be due to exposures during embryonic development to these or other pollutants. Future studies must determine if a causal relationship exists between the contaminants found in alligator eggs and abnormalities observed in the hatchlings and persisting in juveniles.

Mercury Distribution in Blood, Tissues, and Feathers of Double-Crested Cormorant Nestlings from Arid-Lands Reservoirs in South Central New Mexico by C. A. Caldwell; M. A. Arnold; W. R. Gould (pp. 456-461).

Eggs, blood, liver, muscle, and feathers were analyzed for concentrations of total mercury in double-crested cormorant (Phalacrocorax auritus) nestlings from two reservoirs in south central New Mexico. Total mercury concentrations among eggs, tissues, and feathers were not significantly correlated. Concentrations of total mercury averaged 0.40 μg/g in liver and 0.18 μg/g in muscle tissues in both populations of nestlings. There were no significant changes in concentrations of total mercury in whole blood of nestlings collected 7–10 days and 17–22 days posthatch in Caballo Reservoir (0.36 μg/g and 0.39 μg/g, respectively) and in Elephant Butte Reservoir (0.36 μg/g and 0.34 μg/g, respectively). Total mercury concentrations were similar for blood, muscle, and liver in nestlings for both reservoirs. Total mercury concentrations were higher in eggs and tail, primary, and secondary feathers from nestlings at Caballo Reservoir compared to Elephant Butte Reservoir. Although there were no differences in concentrations of total mercury in fishes between the two reservoirs, bioaccumulation and biomagnification was evident in planktivorous and piscivorous fishes. The data demonstrate that feather analysis may not be a good predictor of tissue burden in nestlings from regions of low contamination.

Butyltin Compounds in River Otters (Lutra canadensis) from the Northwestern United States by K. Kannan; R. A. Grove; K. Senthilkumar; C. J. Henny; J. P. Giesy (pp. 462-468).

Butyltin compounds, including mono-, di-, and tributyltin (MBT, DBT, and TBT) were measured in livers of 40 adult river otters (Lutra canadensis) collected from rivers and coastal bays in Washington and Oregon, USA. Butyltins were found in all the river otters, at a concentration range of 8.5–2,610 ng/g, WW. The greatest concentration of total butyltins of 2,610 ng/g, WW, was found in a river otter collected in Puget Sound from Fort Ward, Washington. River otters collected near areas with major shipping activities, such as the Puget Sound, contained significantly greater concentrations (geometric mean: 367 ng/g, WW) of butyltins than those from rivers. Among butyltin compounds, MBT and DBT predominated in livers. The concentrations of butyltins in river otters ranged from comparable (Puget Sound) to less (rivers) than what was found in coastal cetaceans.

Immunological, Hematological, and Biochemical Responses in Immature White-Footed Mice Following Maternal Aroclor 1254 Exposure: A Possible Bioindicator by P. J. Wu; E. H. Greeley; L. G. Hansen; M. Segre (pp. 469-476).

A number of hematological, immunological, and biochemical parameters were measured in Peromyscus leucopus pups born from dams exposed to a single dose (300 mg/kg body weight) of Aroclor 1254. To increase the chances of uncovering even modest consequences of the exposure, in one protocol the pups were weaned at 3 weeks and examined at 6 weeks of age, while in a second protocol the pups were kept with their mother for 4 weeks, at which time they were examined. The older pups showed significant decreases in body weight, ratio of spleen weight to body weight, numbers of peripheral white blood cells and lymphocytes, and number and percentage of monocytes. They also showed significant increases in the stimulation index in response to the mitogen phytohemagglutinin (PHA), percentage of peripheral blood neutrophils and liver EROD induction. Pups sacrificed at 4 weeks of age showed even more significant differences. Their body and liver weights, percentage and number of peripheral blood lymphocytes, and serum antibody titers were significantly lower than those of their controls, while spleen to body weight ratios, percent of neutrophils in their peripheral blood, and liver EROD, PROD, and BROD levels were significantly higher than those of the controls. The primary implication of this work is that white-footed mouse pups could be used as biomonitors of contaminated sites. Females could be captured at the sites and bred in captivity with normal males. The vulnerable parameters identified in this study could then be measured in the resulting offspring and compared with a database collected from normal pups.

Reducing Dust, Lead, Dust Mites, Bacteria, and Fungi in Carpets by Vacuuming by J. W. Roberts; W. S. Clifford; G. Glass; P. G. Hummer (pp. 477-484).

Old carpets may be reservoirs of dust, lead (Pb), and dust mite allergen. The purpose of this study was to determine if the dust, Pb, dust mite allergen, bacteria, and fungi on the surface of carpets could be reduced by 90% in 1 week with the use of a Hoover Self Propelled Vacuum with Embedded Dirt Finder (HSPF). A high-volume surface sampler (HVS3) was used to measure surface dust and pollutants before and after the use of the HSPF to remove deep dust in carpets 12 to 20 years old in nine middle-class homes and two small offices. The minimum, median, and maximum surface loading for the first and final samples are as follows: first fine dust loading: min 0.32 g/m², max 14.4 g/m², median 1.30 g/m²; final fine dust loading: min 0.019 g/m², max 0.289 g/m², median 0.102 g/m²; first Pb loading: min 38 μg/m², max 3,871 μg/m², median 471 μg/m²; final Pb loading: min 13 μg/m², max 2,023 μg/m², median 86 μg/m²; first mite loading: min 0.11 μg/m², max 12.88 μg/m², median 2.82 μg/m²; final mite loading: min 0.06 μg/m², max 3.67 μg/m², median 0.28 μg/m². Data were insufficient to determine if the loadings of bacteria and fungi were reduced a similar amount. Six to 45 min/m² of vacuuming with the HSPF removed deep dust from these carpets. The median surface loadings of fine dust, Pb, and dust mite allergen in these 11 carpets were reduced by 91, 82, and 94%, respectively, in 1 to 15 h of vacuuming. The loading of the deep dust collected with the HSPF ranged from 8 to 171 g/m² with a median of 66 g/m².

Glove Permeation Tests Using Novel Microchemical Techniques for 2,4-Dichlorophenoxyacetic Acid (2,4-D) Derivatives by Y.-W. Lin; S. S. Que Hee (pp. 485-489).

The aim was to assess the permeation of different herbicide emulsion concentrate formulations of 2,4-dichlorophenoxyacetic acid (2,4-D) as 60.8 and 83.5% butoxyethyl ester (BEE) and 46.8% dimethyl amine salt (DMAS) through four types of glove materials (lined unsupported nitrile, unlined unsupported butyl, Silver Shield laminate, and Viton). This entailed the development of new microchemical techniques to allow sensitive capillary gas chromatography/mass spectrometry (GC/MS) of the permeated herbicide. The 2,4-D DMAS was esterified to the methyl ester by boron trifluoride-methanol complex with 99.2 ± 3.7% efficiency using microwave heating to minimize reaction time and to process microsamples. The GC/MS detection limit was 5 ng/ml (ppb) of 2,4-D DMAS in the collection medium. The permeates from the ester formulations were analyzed directly for the ester above the detection limit of 9 ng/ml (ppb) BEE. The permeation investigations utilized the American Society for Testing Materials (ASTM)-type permeation cells with liquid collection media. The results showed that these gloves could provide at least 6 h protection for these formulations.

Multiroute Exposure Assessment and Excretion of Urinary Metabolites of Fenitrothion During Manual Operations on Treated Ornamental Plants in Greenhouses by C. Aprea; G. Sciarra; P. Sartorelli; F. Ceccarelli; L. Centi (pp. 490-497).

The results of environmental and biological (five subjects) monitoring of exposure to fenitrothion during manual operations on treated ornamental plants in greenhouses are reported. Urinary excretion [GM (GSD)] of alkylphosphates [dimethylphosphate (DMP) + dimethylthiophosphate (DMTP)] (nmol/g creat) was 244.8 (1.8), 174.0 (2.0), and 354.4 (1.6) respectively, on the first (Monday), third (Wednesday), and fifth (Friday) days of work. These levels were not significantly higher than those recorded in a control group (21 subjects) in which urinary excretion [GM (GSD)] of DMP + DMTP was 102.8 (4.2) nmol/g creat. Air concentrations of fenitrothion (nmol/m³) ranged from 45.5 to 81.2 on Monday, 17.3 to 27.1 on Wednesday, and 9.7 to 19.1 on Friday. Dose estimates showed that the respiratory-absorbed doses of fenitrothion accounted, on the average (GM), for 94.7%, 93.1%, and 91.5% of the total absorbed dose on Monday, Wednesday, and Friday, respectively. Multiple regression analysis showed a significant correlation (r² = 0.595) between urinary excretion of DMP + DMTP, respiratory-absorbed dose, and skin-absorbed dose, estimated on Monday and Wednesday. Total estimated absorbed doses did not exceed the acceptable daily intake for fenitrothion. Serum and erythrocyte cholinesterase activities were not significantly different before and after exposure.

Effect of Changes in Excretion of Persistent Organochlorine Compounds with Human Breast Milk on Related Exposure of Breast-Fed Infants by K. Czaja; J. K. Ludwicki; K. Góralczyk; P. Struciński (pp. 498-503).

This study was an attempt to identify if there are any trends in excretion of 1,2,3,4,5,6-hexachlorocyclohexane (HCH) isomers α-, β-, and γ-, hexachlorobenzene (HCB), [1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane] (p,p′-DDT), [1,1-dichloro-2,2-bis(4-chlorophenyl)ethane] (p,p′-DDD), [1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene] (p,p′-DDE), and polychlorinated biphenyls (PCBs) with human milk during lactation. The shortest lactation studied took 16 weeks, and the longest 84 weeks. Three hundred fifty-two milk samples, collected from each donor once a week, were examined. The analysis of the result showed individual differences in the excretion of the compounds. The findings from this study are not conclusive enough to claim that there are consistent trends showing a decrease or increase in the excretion of the compounds under examination. Thus, one cannot claim that the infants' exposure to those compounds decreases or increases as breast-feeding continues.

Letter to the Editor by Mary S. Wolff (pp. 504-504).

Announcement (pp. 505-505).

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Archives of Environmental Contamination and Toxicology (v.36, #4)