Levels of polychlorinated dibenzo-p-dioxins and dibenzofurans in cattle raised at agricultural research facilities across the USA and the influence of pentachlorophenol-treated wood.

Adipose tissue samples from 158 cattle raised locally at experiment stations across the USA were analysed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F). While 80% of the samples had PCDD/F concentrations that fell within the range of a previous US survey of beef animals (not detected -4.1 ppt toxic equivalency), several animals had exceptionally high concentrations (8-54 ppt toxic equivalency). The investigations of three facilities where highly contaminated animals were raised found pentachlorophenol-treated wood at each site. The congener pattern in the animals' tissues and the lack of elevated PCDD/F levels in other environmental samples, i.e. hay and soil, indicated that the treated wood was the source of contamination. A congener pattern similar to that of pentachlorophenol-exposed animals was seen for the means and medians of the entire data, i.e. OCDD, HpCDD and 1,2,3,6,7,8-HxCDD dominated, the PCDD concentrations equalled or exceeded the furan concentrations, and the concentration of 1,2,3,6,7,8-HxCDD was six times that of the other HxCDD isomers. This suggested that pentachlorophenol-treated wood contributed measurably to many of the animals in this survey. The largest contributors to the median toxic equivalencies were 1,2,3,7,8-PeCDD (40%) and 1,2,3,6,7,8-HxCDD (16%). No clear geographical trends emerged from the data.

An investigation of the in vivo formation of octachlorodibenzo-p-dioxin.

The in vivo formation of dioxins from chemical precursors was investigated in rats. Sprague-Dawley rats were fed pentachlorophenol or a predioxin in peanut oil for 14 days. Mass balance calculations indicated that pentachlorophenol was not converted to dioxins; however, the predioxin, nonachloro-2-phenoxyphenol, was converted to OCDD. Conversion of the predioxin ranged from 0.5% to 153% and depended on the amount of predioxin and OCDD present in the diet. The analytical procedures used for sample preparation did not appear to cause conversion of the predioxin to OCDD. The mechanism for biological conversion may be enzymatic or spontaneous.

Chlorinated dibenzo-p-dioxin and dibenzofuran concentrations in beef animals from a feeding study.

Four calves were fed polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans for 120 days at levels somewhat higher than what may be found in forage near some waste incinerators and manufacturing plants. Four calves were fed identical diets but without the chemicals. Using bioelectrical impedance measurements of total body fat, 30-50% of the dosed 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, and 2,3,4,7,8-PeCDF was estimated to be retained by the animals. Although these same congeners were bioconcentrated in adipose tissue (BCF approximately 10), consumer products such as ribeye showed concentrations less than what were found in the animal feed (BCF approximately 0.1). Distribution of the dioxins and furans into various lipid compartments appeared to be rather uniform in back fat, perirenal fat, and ribeye for tetra to hexa congeners. Ribeye, serum, and liver lipids had higher concentrations of the higher chlorinated congeners, due in part to not reaching a steady state. An unexpected source of dioxin and furan contamination was discovered during the experiment, resulting in the control animals having concentrations of some congeners that were equal to or in some cases greater than those of the dosed animals. Pentachlorophenol-treated wood components in the pole barn where the feeding experiment was conducted were found to have contributed to the animals' exposure.

Sources and fate of polychlorinated dibenzodioxins, dibenzofurans and related compounds in human environments.

Several of the major incidents resulting in potential human exposures to polychlorinated dibenzodioxins (PCDDs) and/or polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs) and related compounds which have occurred in the U.S. in recent periods have resulted from improper disposal of hazardous chemical wastes. Prominent examples of such environmental contamination episodes are the Love Canal, into which ton quantities of chlorinated organic compounds containing substantial concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were deposited; numerous sites in the State of Missouri which were contaminated by the dumping of chlorinated organic wastes containing various PCDDs and possibly PCDFs, and PCBs; and the environs of a 2,4-D/2,4,5-T manufacturing plant site in Arkansas, which were contaminated with PCDDs. Environmental assessments of such sites have revealed extensive contamination of soils, waterways, fish and other biological species with these toxic compounds, which in turn could lead to human exposures. Other recently identified sources of PCDDs, PCDFs and related compounds in human environments include stack effluents from municipal refuse incineration, and fires and explosions involving electrical devices containing PCBs and polychlorinated benzenes. Data obtained in assessments of such incidents are presented, and the implications of these findings with respect to the distribution and persistence of PCDDs, PCDFs and related chemicals in the environment and possible effects on humans are discussed.

Formation and reactions of negative ions relevant to chemical ionization mass spectrometry. I. CL mass spectra of organic compounds produced by F- reactions.

A systematic study of the negative-ion chemical ionization mass spectra produced by the reaction of F(-) with a wide variety of organic compounds has been accomplished. A time-of-flight mass spectrometer fitted with a modified high pressure ion source was employed for these experiments. The F(-) reagent ion was generated from CF(3)H or NF(3), typically at an ion source pressure of 100 mum. In pure NF(3), F(-) is the major ion formed and constitutes more than 90% of the total ion intensity. While F(-) is also the major primary ion formed in pure CF(3)H, it undergoes rapid ion-molecule reactions at elevated source pressures, yielding (HF)(n)F(-) (n = 1-3) ions, which makes CF(3)H less suitable as a chemical ionization reagent gas. Among the organic compounds investigated were carboxylic acids, ketones, aldehydes, esters, alcohols, phenols, halides, nitriles, nitrobenzene, ethers, amines and hydrocarbons. An intense (M - 1)(-) ion was observed in the F(-) chemical ionization mass spectra of carboxylic acids, ketones, aldehydes and phenols. Alcohols yield only (M + F)(-) ions upon reaction with F(-). A weaker (M + F)(-) ion was also detected in the F(-) chemical ionization spectra of carboxylic acids, aldehydes, ketones and nitriles. The F(-) chemical ionization mass spectra of esters, halides, nitriles, nitrobenzene and ethers are characterized primarily by the ions, RCOO(-), X(-), CN(-), NO(2) (-), and OR(-), respectively. In addition, esters show a very weak (M - 1)(-) ion (except formates). In the F(-) chemical ionization spectra of some aliphatic alkanes and o-xylene, a very weak (M + F)(-) ion was observed. Amines and aliphatic alkenes exhibit only insignificant fragment ions under similar conditions, while aromatic hydrocarbons, such as benzene and toluene are not reactive at all with the F(-) ion. The mechanisms of the various reactions mentioned are discussed, and several experimental complications are noted. In still other studies, the effects of varying several experimental parameters, including source pressure, relative proportions of the reagent and analyte, and other ion source parameters, on the observed chemical ionization mass spectra were also investigated. In a mixture of NF(3) and n-butanol, for example, the ratio of the intensities of the ions characteristic of the alcohol to that of the (HF)(n)F(-) ion was found to decrease with increasing sample pressure, with increasing NF(3) pressure, and with increasing electron energy. No significant effects on the spectra were observed to result from variation of the source repeller field or the source temperature. The addition of argon to the source as a potential moderator did not alter the F(-) chemical ionization spectrum significantly, but the use of oxygen appears to inhibit formation of the (HF)(n)F(-) cluster ion. The advantages of using F(-) as a chemical ionization reagent are discussed, and comparisons are made with other reagent ions.