A national survey of persistent, bioaccumulative, and toxic (PBT) pollutants in the United States milk supply.
(57/332)
This study measured 21 persistent, bioaccumulative, and toxic (PBT) pollutants in the US milk supply. Since milk fat is likely to be among the highest dietary sources of exposure to PBTs, it is important to understand their levels in this food. Nationwide samples were collected from 45 dairy plants in July of 2000 and again in January 2001. The levels of all chemicals in the chlorobenzene, pesticide and other halogenated organic groups were determined to be below their detection limits in all samples. National averages were computed for 11 chemicals or chemical groups found above the detection limits. The national average CDD/CDF and PCB TEQ concentrations were 14.30 and 8.64 pg/l, respectively, for a total of 22.94 pg/l. These levels are about half the values found in a similar study conducted in 1996. If this difference is in fact indicative of declining milk levels and assuming exposure levels from nondairy pathways have remained the same over this time period, this would result in an overall decrease in adult background dioxin exposure of 14%. Six PAHs were detected with national averages ranging from 40 to 777 ng/l. Cadmium concentrations ranged from 150 to 870 ng/l with a national average of 360 ng/l. Lead concentrations were consistently higher than those of cadmium, ranging from 630 to 1950 ng/l with a national average of 830 ng/l. PAHs showed the strongest seasonal/geographic differences, with higher levels in winter than summer, north than south and east than west. Average adult daily intakes from total milk fat ingestion were computed for all detected compounds and compared to total intakes from all pathways: CDD/CDF/PCB TEQs: 8 vs. 55 pg/day, PAHs: 0.6 vs. 3 micro g/day, lead: 0.14 vs. 4-6 micro g/day, and cadmium: 0.06 vs. 30 micro g/day. (+info)
Aggregate exposures of nine preschool children to persistent organic pollutants at day care and at home.
(58/332)
In the summer of 1997, we measured the aggregate exposures of nine preschool children, aged 2-5 years, to a suite of organic pesticides and other persistent organic pollutants that are commonly found in the home and school environment. The children attended either of two child day care centers in the Raleigh-Durham-Chapel Hill area of North Carolina and were in day care at least 25 h/week. Over a 48-h period, we sampled indoor and outdoor air, play area soil and floor dust, as well as duplicate diets, hand surface wipes, and urine for each child at day care and at home. Our target analytes were several polycyclic aromatic hydrocarbons (PAH), organochlorine pesticides, and polychlorinated biphenyls (PCB); two organophosphate pesticides (chlorpyrifos and diazinon), the lawn herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), three phenols (pentachlorophenol (PCP), nonyl phenols, and bisphenol-A), 3,5,6-trichloro-2-pyridinol (TCP), and two phthalate esters (benzylbutyl and dibutyl phthalate). In urine, our target analytes were hydroxy-PAH, TCP, 2,4-D, and PCP. To allow estimation of each child's aggregate exposures over the 48-h sampling period, we also used time-activity diaries, which were filled out by each child's teacher at day care and the parent or other primary caregiver at home. In addition, we collected detailed household information that related to potential sources of exposure, such as pesticide use or smoking habits, through questionnaires and field observation. We found that the indoor exposures were greater than those outdoors, that exposures at day care and at home were of similar magnitudes, and that diet contributed greatly to the exposures. The children's potential aggregate doses, calculated from our data, were generally well below established reference doses (RfDs) for those compounds for which RfDs are available. (+info)
Synthesis and characterization of hexadecadienyl compounds with a conjugated diene system, sex pheromone of the persimmon fruit moth and related compounds.
(59/332)
Hexadecadien-1-ol and the derivatives (acetate and aldehyde) with a conjugated diene system have recently been identified from a pheromone gland extract of the persimmon fruit moth (Stathmopoda masinissa), a pest insect of persimmon fruits distributed in East Asia. The alcohol and acetate showed their base peaks at m/z 79 in a GC-MS analysis by electron impact ionization, but the aldehyde produced a unique base peak at m/z 84, suggesting a 4,6-diene structure. To confirm this inference, four geometrical isomers of each 4,6-hexadecadienyl compound were synthesized by two different routes in which one of two double bonds was furnished in a highly stereoselective manner. Separation of the two isomers synthesized together by each route was facilely accomplished by preparative HPLC. Their mass spectra coincided well with those of natural components, indicating that they were available for use as authentic standards for determining the configuration of the natural pheromone. Furthermore, other hexadecadienyl compounds, including the conjugated diene system between the 3- and 10-positions, were synthesized to accumulate the spectral data of pheromone candidates. 5,7-Hexadecadienal interestingly showed the base peak at m/z 80; meanwhile, the base peaks of its alcohol and acetate were detected at m/z 79 like the corresponding 4,6-dienes. The base peaks of all 6,8-, 7,9-, and 8,10-dienes universally appeared at m/z 67 like 9,11-, 10,12-, and 13,15-dienes, the spectra of which have already been published. Although 3,5-hexadecadienal was not prepared, base peaks at m/z 67 and 79 were recorded for the alcohol and acetate, respectively. (+info)
Isolation and characterization of aromatics-degrading microorganisms from the gut of the lower termite Coptotermes formosanus.
(60/332)
We isolated aromatics-degrading bacteria from the gut of a lower termite, Coptotermes formosanus, using a mineral salt medium containing various aromatic compounds as the sole carbon source. Two species, Burkholderia sp. strain VE22 and Citrobacter sp. strain VA53, were isolated by aerobic enrichment culture with veratraldehyde and vanillin, respectively. Strain VA53 could also grow and metabolize vanillin anaerobically. (+info)
Detection and enumeration of aromatic oxygenase genes by multiplex and real-time PCR.
(61/332)
Our abilities to detect and enumerate pollutant-biodegrading microorganisms in the environment are rapidly advancing with the development of molecular genetic techniques. Techniques based on multiplex and real-time PCR amplification of aromatic oxygenase genes were developed to detect and quantify aromatic catabolic pathways, respectively. PCR primer sets were identified for the large subunits of aromatic oxygenases from alignments of known gene sequences and tested with genetically well-characterized strains. In all, primer sets which allowed amplification of naphthalene dioxygenase, biphenyl dioxygenase, toluene dioxygenase, xylene monooxygenase, phenol monooxygenase, and ring-hydroxylating toluene monooxygenase genes were identified. For each primer set, the length of the observed amplification product matched the length predicted from published sequences, and specificity was confirmed by hybridization. Primer sets were grouped according to the annealing temperature for multiplex PCR permitting simultaneous detection of various genotypes responsible for aromatic hydrocarbon biodegradation. Real-time PCR using SYBR green I was employed with the individual primer sets to determine the gene copy number. Optimum polymerization temperatures for real-time PCR were determined on the basis of the observed melting temperatures of the desired products. When a polymerization temperature of 4 to 5 degrees C below the melting temperature was used, background fluorescence signals were greatly reduced, allowing detection limits of 2 x 10(2) copies per reaction mixture. Improved in situ microbial characterization will provide more accurate assessment of pollutant biodegradation, enhance studies of the ecology of contaminated sites, and facilitate assessment of the impact of remediation technologies on indigenous microbial populations. (+info)
Immobilized native bacteria as a tool for bioremediation of soils and waters: implementation and modeling.
(62/332)
Based on 3,4-dihydroxyphenylacetate (3,4-DHPA) dioxygenase amino acid sequence and DNA sequence data for homologous genes, two different oligonucleotides were designed. These were assayed to detect 3,4-DHPA related aromatic compound-degrading bacteria in soil samples by using the FISH method. Also, amplification by PCR using a set of ERIC primers was assayed for the detection of Pseudomonas GCH1 strain, which used in the soil bioremediation process. A model was developed to understand and predict the behavior of bacteria and pollutants in a bioremediation system, taking into account fluid dynamics, molecular/cellular scale processes, and biofilm formation. (+info)
Toxicity of flare and crude hydrocarbon mixtures.
(63/332)
The toxicity of whole, saturate, and aromatic hydrocarbon mixtures from flare pit and crude oil sources were evaluated using Lumbricus terrestris. Body burden analysis was used to analyze the intrinsic toxicity of the six hydrocarbon mixtures. The major fractions of the whole mixtures, the saturate, and aromatic fractions had different intrinsic toxicities; the aromatics were more toxic than the saturates. The toxicity of the saturate and aromatic fractions also differed between the mixtures. The flare saturate mixture was more toxic than the crude saturate mixture, while the crude aromatic mixture was more toxic than the flare aromatic mixture. The most dramatic difference in toxicity of the two sources was between the flare whole and crude whole mixtures. The crude whole mixture was very toxic; the toxicity of this mixture reflected the toxicity of the crude aromatic fraction. However, the flare whole mixture was not toxic, due to a lack of partitioning from the whole mixture into the lipid membrane of the exposed worms. This lack of partitioning appears to be related to the relatively high concentrations of asphaltenes and polar compounds in the flare pit whole mixture. (+info)
Effects of sewage sludges contaminated with chlorinated aromatic hydrocarbons on sludge-treated areas (soils and sediments).
(64/332)
The fate of PCDDs, PCDFs, and PCBs in sewage sludges after different management techniques--such as agricultural application, land restoration, and marine disposal--was studied. Changes observed in the concentrations, in the ratio between PCDD and PCDF levels, and in the isomeric distribution suggest the influence of the sewage sludge on the sludge-treated areas (soils and sediments). Whereas land application techniques seem to produce no serious environmental consequences, marine disposal practices produce considerable increases in the levels of contamination in marine sediments. (+info)