Concentrations Of DDT Residues Research Articles

Risk Assessment of Dichlorodiphenyltrichloroethane Residues in Soil and Rice Samples Harvested in Selected Rice Farms of Benue State, Nigeria

This work investigates the level of Dichlorodiphenyltrichloroethane (DDT) residues in soil and rice samples collected from Otukpo farmland area of Benue State. Ten soil samples and five different species of rice samples were collected from the farmlands to determine the concentration of DDT residues. Standard analytical methods were employed for the determination of some physicochemical parameters (pH, total organic carbon, moisture content and cation exchange capacity) of the samples. Collected samples were analyzed for residues of total dichlorodiphenyltrichloroethane using gas chromatography mass spectrometry (GC-MS) after careful extraction and cleanup. Risk assessment was carried out by determining the hazard indices. The results of the physicochemical analysis showed that the mean pH value of soil samples is 6.2 indicating slight acidity as compared to rice 7.34 which is approximately neutral and within WHO acceptable limits. The mean total organic carbon (TOC) value is 14.57% while the mean cation exchange capacity is 7.85 meq/100g in soil. DDT was detected with average concentration of 10.5 mg/kg in soil and 3.41 mg/kg in rice which is above the EU/WHO and MRL recommended rate of 0.1 mg/kg and 0.05 mg/kg. Harzard indices employed in this research shows that rice species are fit for consumption with the exception of those with Hazard Index level greater than one in children. The contamination levels of DDT in the analyzed soil based on national standards are considered toxic for crop production but analysis shows that the uptake level of DDT from soil to crop is very low which makes the rice cultivaled fit for consumption.

Assessment of organochlorine and organophosphorus pesticides in various meats samples of maharashtra-india using gas chromatography

Chronic pesticide toxicity, recognized as a major health hazard in human food chain, comprises of foods from animal source. Devising analytical methods for estimating pesticide residues will help to monitor the status of these contaminants in animal source foods. In this study, two pesticide groups viz., organochlorine (OC) and organophosphorus (OP) compounds were selected to detect pollutants in various meat samples. To detect these pesticides gas chromatography (GC) method was used, standardized and validated. Validation studies on meat samples included accuracy, precision, linearity, limit of detection and quantification. A total of 240 numbers of meat samples of chicken, buffalo, sheep/goat and pig were collected from three different regions of Maharashtra and used in validation studies. The mean concentration of DDT residues in the chicken, buffalo, sheep/goat and pig meat was found to be 27.34, 10.67, 76.33 and 44.12 pg/kg, respectively. Mean concentration of HCH residues in chicken and pig meat was found to be 7.50 and 112.20 pg/kg, and was not detected in buffalo and sheep/goat meat. Mean concentration of Endosulfan and Aldrin residues in chicken, buffalo and sheep/goat meat were found to be 51.09, 23.18, 211.37 pg/kg and 111.48, 81.85, 54.79 pg/kg, respectively. Chlorpyrifos was not detected in any of the meat samples collected. However, the values of pesticide residue concentration in all the 240 nos. of meat samples were found to be below the MRLs values set by Codex Alimentarius Commission and European Commission Regulation (EC) No. 149/2008. Therefore, it is concluded that the standardized GC method can be used for the detection of pesticides in different matrices.

Levels and distribution of pesticide residues in soil and sediments in Eastern Lake Tanganyika environs

The aim of this study was to investigate the types, levels and distribution of pesticide residues in Eastern Lake Tanganyika basin in Tanzania. Water, soil and sediments samples were collected from various sites in Kigoma region. Analyses of cleaned sample extracts were performed using gas chromatographyelectron capture detection (GC-ECD) and gas chromatography-mass spectrometry (GC-MS). Six pesticide residues and metabolites were detected, namely, p,p' -DDT, o,p' -DDT, p,p' -DDE, p,p' -DDD, diazinon and chlorpyrifos. DDT, DDD and DDE were the predominantly detected compounds in all of the samples. Diazinon and chlorpyrifos were detected in soil samples only. The highest concentrations of total DDT in sediments and soil ranged from 10.02 to 116 μg/kg dry weight (dw) and 7.5 to 564.2 μg/kg dw, respectively. Chlorpyrifos and diazinon had concentrations up to 36 and 184 μg/kg dw, respectively. The concentrations of DDT residues were greater in soil samples than in sediments. The highest concentrations of DDT residues were detected in soil samples. The ratios of ( p,p' -DDE + p,p' -DDD)/ p,p' -DDT indicated recent inputs in most samples. The study reveals that there were recent uses of DDT, diazinon and chlorpyrifos in the region. Continued use of DDT indicates risks and may result into serious environmental problems. The area therefore needs serious environmental monitoring. © 2017 International Formulae Group. All rights reserved. Keywords: Pesticide, Lake, soil, sediments, Tanzania

Dichlorodiphenyltrichloroethane (DDT) and its metabolites in dairy milk and milk products of Agra City, India

bovine milk, milk products and in the environmental samples has been reported. Therefore, a study was undertaken to monitor the trace levels of DDT and its metabolites in dairy milk and butter samples of Agra city, India to assess the risk to the consumers and seasonal variability. Analysis of DDT from milk and butter samples were done by using the method standardized in the laboratory. During the year 2002-2003 milk samples were collected for the analysis of DDT and its metabolites in different seasons viz. winter, summer and rainy season. During winter seasons 28 samples of milk were analyzed and only 19 samples were found to be positive with the o, p-DDT, p, p-DDT and p, p-DDE metabolites of DDT while in summer and rainy seasons only 15 and 20 were found positive from out of 28 and 27 samples. The total DDT (o, p-DDT, +p, p-DDT+p, p-DDE) residues were 36.8 9, 33.2 9, 23.9x10 9 during winter, summer and rainy seasons, respectively. In the present study, during 2002-2003 out of 83 dairy milk samples only 54 (65.10%) were found to be positive with DDT residues. Similarly, out of 21, 20 and 19 butter samples, 13, 12 and 12 samples were positive with DDT residues. The total DDT residue concentrations were 26.1  10 9, 23.8 10 -9 and 22.4 10 -9 during winter, summer and rainy seasons, respectively. Tolerance limit for the DDT residues in milk and butter samples is 0.05x10 "6 (on whole milk basis) and 1.25 -6 prescribed by prevention of food adulteration, India (PFA, 1986). None of the milk and butter samples showed total DDT residues above are higher than the tolerance limit. The total DDT concentrations were 36.8 9, 33.2x 10 -9 and 23.9x 10 -9 in winter summer and rainy seasons, respectively while the same pattern of residues was observed in butter samples. Maximum permissible intake (MPI) and theoretical maximum residue contribution (TMRC) were calculated for DDT in milk and butter. These values also indicated that milk and butter are safe for consumption.

DDT and HCH residues in dairy milk samples collected from different geographical regions of India: a multicentre study

Under a multicentre study conducted by the Indian Council of Medical Research, 2205 samples of dairy milk were collected from rural and urban areas of 12 states representing different geographical regions of India. These samples were analysed for residues of DDT and different isomers of HCH by gas-liquid chromatography. Analytical quality assurance between various participating laboratories was ensured through analysis of check samples. The residues of DDT and HCH were detected in more than 80% of samples analysed. Concentrations of DDT residues, α-HCH, β-HCH, γ-HCH and δ-HCH exceeded their maximum residue limits prescribed by the Ministry of Health and Family Welfare of the Indian Government in 37, 21, 42, 28 and 4% of the samples, respectively. Median values of DDT a d HCH found in dairy milk in India were more than the corresponding values reported from most other countries. The results showed significant variations in the incidence as well as level of these contaminants in dairy milk from different regions of the country.

Polychlorinated Biphenyls and Chlorinated Pesticides in Bird Eggs from Calabria (Southern Italy)

Polychlorinated biphenyl (PCB) and chlorinaed pesticide levels in eggs of two terrestrial (kestrel and sparrowhawk) and two aquatic (heron and mallard) birds were determined in inhabited areas and woodlands of Calabria. The eggs of the two terrestrial raptors were more polluted than those of the aquatic birds. Among the raptors, the kestrel demonstrated the highest level of pollution because it lives close to villages, whereas sparrowhawk lives in forests. The highest PCB and DDT residue concentrations found in kestrel (11.3 and 8.7 mg g−1lipid, respectively) could cause shell thinning. Aquatic species show a higher DDT/DDE ratio than terrestrial species, probably because DDT is degraded more slowly in aquatic environments. However, point DDT sources seem to be present in this region.

Polychlorinated biphenyls and organochlorine pesticides in EELS ( Anguilla anguilla L.) from Welsh rivers

Organochlorine concentrations in the muscle tissues of eels at 41 freshwater sites across Wales were surveyed in 1993. Positive but weak relationships were detected between eel age or length and the concentration of some organochlorines. Isomers of HCH were below detection at most sites. Dieldrin was widespread at 10–100 μg kt −1 wet weight, despite its ban in sheep dip in 1989. Total DDT residue concentrations averaged 73 μg kg −1. Total PCB burdens expressed as Arochlor 1260, were > 50 μg kg −1 at 76% of sites and > 100 μg kg −1 at 46% of sites. The range of concentrations was comparable with other UK data. Rural sites had relatively low levels of PCBs, highest contamination occurring in the lower reaches of industrialised catchments. The inferences for environmental effects are discussed.

Occurrence and Consequences of DDT Residues in Woodland Birds Following Tsetse Fly Spraying Operations in NW Zimbabwe

1. Concentrations of DDT and its metabolites were compared over space, time, feeding strategy and diet in the striped kingfisher Halcyon chelicuti, red-billed wood-hoopoe Phoeniculus purpureus and five songbird species ; white-headed black chat Thamnolaea arnoti, black tit Parus niger, chinspot flycatcher Batis molitor, white helmet shrike Prionops plumatus and white-browed sparrow-weaver Plocepasser mahali. 2. The white-browed sparrow-weaver fed mainly on seeds but the remaining species were insectivorous. The kingfisher, chat and helmet shrike fed heavily on secondary consumers. 3. DDT residue concentrations 1-3 months after treatment reflected feeding site more than diet. Geometric means varied between species by up to 15 times. Highest concentrations were found in the wood-hoopoe and chat, which sometimes foraged on sprayed tree trunks, while lowest concentrations were found in the flycatcher and helmet shrike, which foraged mainly in tree and shrub canopy. 4. Depending on species, geometric mean concentrations of DDT equivalents fell from 90-1300 μg g -1 lipid weight at 1-3 months post treatment to 16-87 μg g -1 lipid weight at 14-17 months. The proportion of DDE in ΣDDT increased from 23-77% to 69-98% over the same period. Interspecific variation at 14-17 months still reflected feeding site rather than trophic accumulation. 5. Populations of the wood-hoopoe and chat declined over 2-3 years in sprayed areas by about 90%, but no differences attributable to spraying were detected in the other species.

Contamination of bovine (buffalo, Bubalus bubalis (L.)) milk from indoor use of DDT and HCH in malaria control programmes

Samples of bovine (Buffalo, Bubalus bubalis (L.)) milk collected from randomly selected houses of Ludhiana and Sangrur districts of Punjab, India, where DDT and HCH, respectively, had been sprayed for the control of malaria, were analysed for insecticide residues between September 1985 and June 1986. The average concentration of DDT residues in samples from the DDT sprayed area were ∼ 4–12 times higher than those in the corresponding samples from HCH sprayed areas. Mean levels of HCH residues in samples from the HCH sprayed area were greater than those in samples from DDT sprayed areas by factors of 2–11. Milk samples collected from four rural houses in each district before and after applications of DDT or HCH for mosquito control also showed that indoor use of these insecticides results in a substantial increase in residue levels. About 74% of the samples analysed contained DDT residues above the extraneous residue limit of 0.05 mg kg −1 (whole milk basis). Estimated maximum daily intakes of DDT and β-HCH through consumption of contaminated milk by 1–3-year-old children exceeded their acceptable daily intakes by nearly three and five times, respectively.

Global distribution and atmospheric transport of chlorinated hydrocarbons: HCH (BHC) isomers and DDT compounds in the Western Pacific, Eastern Indian and Antarctic Oceans

Concentrations of chlorinated hydrocarbons such as HCH isomers and DDT compounds were determined in air and surface water samples taken from the Western Pacific, Eastern Indian and Antarctic Oceans. The most interesting finding was their presence in measurable concentrations in the Antarctic Ocean. Chlorinated hydrocarbon pesticides are widely distributed in the open ocean environment over both the northern and southern hemispheres, and some characteristic distribution patterns of pesticide species in different oceanic regions were observed both in air and water samples. HCH residues found in the northern hemisphere were much higher in concentration than those in the southern hemisphere. On the other hand, higher concentrations of DDT residues were found in the tropical regions, but their levels were not so different between both the northern and southern hemispheres. HCH isomers found in the northern hemisphere had the following order of concentrations:α-HCH>γ HCH>β-HCH, while in the southern hemisphereγ-HCH was apparently dominant. DDT compound compositions were rather uniform in all the oceans surveyed, and more than 50% wasp,p′-DDT. These facts can be explained by the world wide situation regarding pesticide use and the physicochemical properties of the pesticides such as their vapor pressures and water solubilities. In addition, the meridional circulation of the atmosphere, particularly the mass flows of the Hadley and Ferrel cells in the troposphere, also contributes to the atmospheric transport and global distribution of these pesticides.

DDT residues in samples of human milk, and in mothers' and cord blood serum, in a continental town in Croatia (Yugoslavia).

Concentrations of p,p'-DDE, p,p'-DDD, and p,p'-DDT were determined in 34 samples of human milk obtained 3-5 days after delivery and in 37 samples obtained at later times of lactation (up to 55 weeks). All samples contained p,p'-DDE, but only several contained p,p'-DDD and p,p'-DDT. The concentrations of p,p'-DDE were 31 microgram/l in the beginning of lactation and 53 microgram/l at later time intervals. The concentration ranges in both groups overlap almost completely and the difference in the mean values is not significant. Serum samples from 35 mothers and cord blood were also analyzed. All samples contained p,p'-DDE, the concentrations being 18 microgram/l and 6.8 microgram/l in the mothers' and cord blood serum, respectively. Serum samples of 24 non-pregnant women contained the same amount of p,p'-DDE (20 microgram/l) as mothers' sera. All samples were collected in a continental town of Croatia (Yugoslavia) between 1977 and 1979. The concentrations of DDT residues were determined by gas chromatography, and two methods for extraction from milk were used and compared.

Blue crab mortality: Interaction of temperature and DDT residues

Serial observations of DDT-contaminated and uncontaminated salt marshes in the norther Gulf of Mexico were made in November and December, 1973. Blue crab (Callinectes sapidus) mortalities observed in the DDT-contaminated marsh during this period were correlated with reduced daily temperature minima. Gas chromatographic analysis of hepatopancreas and swimmeret muscle tissue of dead and dying crabs revealed total DDT residue concentrations as high as 39.0 ppm and 1.43 ppm, respectively. It is suggested that the DDT body burdens and reduced temperatures interact to produce acutely toxic effects. Several physiological and behavioral mechanisms are proposed.

Fertility, Hatchability and Progeny Performance of Laying Hens Fed High Levels of DDT in the Diet

Three groups of White Leghorn hens were fed a commercial laying ration supplemented with 0, 300 or 600 p.p.m. technical DDT for 93 days prior to and during a 40 day measurement period. Fertility, hatchability, chick mortality, chick body weight and chick liver and adipose tissue DDT residues were studied. Egg production was reduced by both 300 and 600 p.p.m. in the hens diet. Fertility was significantly reduced in the 300 but not in the 600 p.p.m. group when compared to the 0 p.p.m. group. There were no significant differences in the hatchability of fertile eggs. Chick mortality was significantly increased in the 300 (7.6% mortality) and 600 p.p.m. (76.5% mortality) groups and chick body weight was significantly decreased in both DDT groups. The majority of the chick mortality in the 600 p.p.m. group occurred in the first three days after hatching. Concentration of DDT residues in chick liver and fat increased as the DDT ingestion by the hens increased.

DDT in New Brunswick Woodcocks

One hundred and sixty-four DDT analyses were conducted on breast muscle of 527 American woodcocks (Philohela minor) collected in New Brunswick during the fall in 1969, 1970, and 1971. DDT residues (= p,p'-DDE + p,p'-DDD + p,p'-DDT) were detected in all samples, the mean concentration of 2.07 ppm (dry weight) being somewhat higher than levels found in 1959-61. Residue levels (wet weight) in woodcocks were directly correlated (P 0.05) in DDT residue concentrations could be attributed to the age of the birds. DDT levels did not change significantly (P > 0.05) in woodcock samples taken from the same site throughout the fall season. There was a significant (P < 0.01) correlation between DDT levels (dry weight) in wings and in breast muscle, indicating the usefulness of wings, which are collected for other purposes, for DDT residue monitoring. J. WILDL. MANAGE. 38(2):331-337 In the course of a pesticide residue monitoring program, prompted by an extensive and prolonged use of DDT against spruce budworm in New Brunswick, 13 woodcocks were collected for the Canadian Wildlife Service in the province during the 1969 hunting season (Pearce and Baird 1971). Total DDT (= p,p'-DDE + p,p'-DDD + p,p'-DDT) residue levels in the breast muscle of some of those samples were high, (weighted mean, 25.4 ppm lipid-weight), relative to the tolerance of 7 ppm in the fat of meat for human food set by the Food and Drug Directorate of the Canada Department of National Health and Welfare. Consequently 46 additional woodcocks were collected by Canadian Wildlife Service and New Brunswick Fish and Wildlife Branch and analyzed during early September 1970, just prior to the scheduled opening of the hunting season. The relatively high DDT content of some of those samples was considered by the Food and Drug Directorate to present an unacceptable potential hazard to human health, with the result that a complete closure of the woodcock hunting season in New Brunswick was agreed on by federal and provincial health and wildlife agencies. Further sampling resulted in a better definition of the area ,'f heaviest contamination and closure of the hunting season in only the central region of the province in 1971 and 1972. The objective of this paper is to present DDT residue data of 527 woodcocks which were collected in New Brunswick in the fall in 1969, 1970, and 1971 so that management decisions could be made to minimize the hazard to the health of the woodcockhunting public. We appreciate the assistance of personnel of the New Brunswick Department of Natural Resources and others, especially F. C. Swan, who collected some of the woodcocks for us. We are greatly indebted to L. M. Reynolds, Ontario Research Foundation (ORF), who conducted all the chemical analyses of the samples, and to J. A. Keith and H. Boyd, Canadian Wildlife Service, for their critical comments on the manuscript. Financial assistance was provided in part by the Canadian National Sportsmen's Show. j. Wildl. Manage. 38 (2):1974 331 This content downloaded from 207.46.13.114 on Thu, 26 May 2016 06:20:18 UTC All use subject to http://about.jstor.org/terms 332 DDT IN WOODCOCKS * Dilworth et al. Table 1. Total DDT residues in breast muscle of woodcocks collected in New Brunswick in 1969, 1970, and 1971. Total no. Total DDT Year Spray history of of breast samples collection sites No. of muscle Mean SE IMean SE collected (lb DDT/acre) analyses samples (ppm wet wt) (ppm lipid wt) 1969 None 2 2 0.02 0.60 2.6 4 11 1.33 0.48 29.9 10.3 1970 None 33 161 0.07 0.02 2.24 0.58 0.5 8 15 0.14 0.03 4.17 1.85 0.6 8 20 0.61 0.46 17.3 5.54 0.7 7 23 0.22 0.08 8.05 3.89 0.9 1 2 0.25 15.8 1.0 2 4 0.20 0.05 7.84 6.04 1.2 3 6 0.51 0.36 26.6 0.94 1.5 6 22 0.16 0.01 5.00 1.78 1.6 1 1 0.42 26.4 2.2 2 2 0.80 65.4 2.6 14 45 2.33 0.54 74.7 28.1 2.8 5 5 1.21 0.81 112 67.0 2.9 2 2 0.66 22.6 1971 None 17 45 0.10 0.03 9.16 3.51 0.1 1 2 0.14 11.7 0.2 1 1 0.13 8.67 0.6 15 35 0.57 0.16 12.8 3.94 1.5 1 1 0.15 4.12 2.2 2 5 0.65 47.5 2.6 21 80 1.38 0.40 58.3 7.22 2.8 3 3 1.59 0.90 116 102 2.9 5 34 0.81 0.46 49.9 28.9

Residues of DDT in Lake Trout (Salvelinus namaycush) and Coho Salmon (Oncorhynchus kisutch) from the Great Lakes

Concentrations of DDT residues were higher in lake trout (Salvelinus namaycush) from southern Lake Michigan in 1966–70 (average 18.1 ppm in fish 558–684 mm long) than in lake trout of the same size-class from Lake Superior in 1968–69 (4.4 ppm), and higher in adult coho salmon (Oncorhynchus kisutch) from Lake Michigan in 1968–71 (averages for different year-classes, 9.9–14.0 ppm) than in those from Lake Erie in 1969 (2.2 ppm). Residues were significantly higher in lake trout from southern Lake Michigan than in those from the northern part of the lake. In lakes Michigan and Superior, the levels increased with length of fish and percentage oil. In Lake Michigan coho salmon, the residues remained nearly stable (2–4 ppm) from September of the 1st yr of lake residence through May or early June of the 2nd yr, but increased three to four times in the next 3 mo. Residues in Lake Erie coho salmon did not increase during this period, which preceded the spawning season. Although the concentrations of total residues in whole, maturing Lake Michigan coho salmon remained unchanged from August 1968 until near the end of the spawning season in January 1969, the residues were redistributed in the tissues of the spawning-run fish; concentrations in the loin and brain were markedly higher in January than in August. This relocation of DDT residues accompanied a marked decrease in the percentage of oil in the fish, from 13.2 in August to 2.8 in January. Concentrations of residues were relatively high in eggs of both lake trout (4.6 ppm) and coho salmon (7.4–10.2 ppm) from Lake Michigan. The percentage composition of the residues (p,p′DDE, o,p′/DDT, p,p′DDT, and p,p′DDT) did not differ significantly with life stage, size, age, or locality, or date of collection of lake trout or coho salmon.

Rate of Uptake of DDT from Soil by Earthworms

SINCE 1958, when the occurrence of DDT and its metabolites in the tissues of earthworms was first reported, there have been more than twenty other reports of DDT residues being found in these animals1,2. The amounts found have differed greatly, ranging from minute traces to concentrations of nearly 700 p.p.m., although concentrations of the order of 1 to 10 p.p.m. have been more commonly reported. Sometimes the concentrations of DDT residues found in the earthworms have been less than in the soil where they live, although the tissues of the worms have usually contained greater concentrations than the surrounding soil. When all the published data were considered, it was seen that there is a linear correlation between the concentration of DDT (and other organochlorine insecticides) in earthworms and that in the corresponding soil1. Not all species concentrate insecticides in the same way or to the same degree3; Lumbricus terrestris and other species with permanent burrows take up DDT from the soil surface more readily than from residues that have been thoroughly mixed into the upper strata of soil. Conversely, some of the species without permanent burrows, that tunnel haphazardly through the upper 150 mm of soil, take up more residues from insecticides evenly distributed through the upper soil layers to plough depth.

DDT residues in Salinas River sediments

The chlorinated hydrocarbon, p,p′ DDT is the most common DDT derivative in bottom sediment samples taken at sites in the Salinas River from the Soledad to the Highway no. 1 river crossing. Its concentration as well as the concentration of total derivatives varies from site to site along the river as well as over time. This is probably due to certain areas acting as natural depositories for water translocated suspended fine particulate matter containing high concentrations of DDT. If the rate of water flow is sufficiently low and if other unspecified natural factors are right, the particles settle and collect at sites along the river yielding a high concentration of DDT residues. Evidence which supports this hypothesis is that the areas with the finest sediment are the areas which also have the highest concentration of DDT derivatives. The portion of the Salinas River south of the Davis river crossing shows the highest concentration of the areas studied.

Effects of Dressing and Cooking on DDT Concentrations in Certain Fish from Lake Michigan

Concentrations of DDT residues were highest in parts of the body with the highest oil content in four species of fish from Lake Michigan: yellow perch (Perca flavescens), bloater (Coregonus hoyi), lake trout (Salvelinus namaycush), and coho salmon (Oncorhynchus kisutch). Dressing reduced the DDT residues and oil content by more than 90% in yellow perch but had little effect in the other three species. The concentration of DDT residues in bloaters was changed little by smoking but was reduced 64–72% by other methods of cooking: from 8.0 ppm (raw) to 2.2 ppm after frying in corn oil; from 10.7 to 3.9 ppm after frying in lard; and from 9.1 to 3.2 ppm after broiling. The concentration of DDT residues in fillets of yellow perch changed only from 0.3 ppm (raw) to 0.4 or 0.5 ppm after baking, frying, or broiling.

DDT in the biosphere: where does it go?

The worldwide pattern of movement of DDT residues appears to be from the land through the atmosphere into the oceans and into the oceanic abyss. Calculations based on the fragmentary data available on. rates of movement and sizes of various pools of DDT residues lead to the conclusion that concentrations in the atmosphere and in the mixed layer of the oceans lag by only a few years behind the amounts of DDT used annually throughout the world. A model suggests that maximum concentrations of DDT residues occurred in air in 1966 and will occur in the mixed layer of the oceans in 1971. The biota probably contains in total less than 1/30 of 1 year's production of DDT during the mid-1960's, a very small amount in proportion to the total potentially available. The reason for the biota's failure to absorb larger quantities and to be affected much more severely is unclear. The analysis suggests that mere good fortune has protected man and the rest of the biota from much higher concentrations, thus emphasizing the need to determine the details of the movement of DDT residues and other toxins through the biosphere and to move swiftly to bring world use of such toxins under rational control based on firm knowledge of local and worldwide cycles and hazards.

DDT in California sea lions.

WE wish to report extraordinary concentrations of DDT residues* in California sea lions, Zalophus californianus, which inhabit year round the coastal waters of California and Baja California, Mexico1. These waters receive agricultural runoff from California valleys where DDT has been used extensively2–4, and where residues have been increasing in the primary stages of some coastal pelagic food chains5.