Coal tar is a complex mixture that exhibits high carcinogenic potency in lungs of animals when administered in the diet. Studies have noted that lung tumor induction does not correlate with the benzo[a]pyrene content of coal tar, suggesting that other hydrocarbons may be involved in the observed tumorigenicity. Our previous studies have demonstrated that a major 'unknown' chemical-DNA adduct is formed in the lung of mice exposed to coal tar. We have used an in vitro rat microsomal activation system to generate the 'unknown' adduct with neat coal tar and fractions of coal tar obtained by chemical fractionation and HPLC. Chemical-DNA adduct formation was evaluated by (32)P-postlabeling using both multi-dimensional TLC and HPLC. GC-MS analysis of the coal tar fractions obtained from HPLC, which produced the 'unknown' adduct in vitro, demonstrated that the adducting hydrocarbon had a mass of 216. A careful evaluation of candidate hydrocarbons led to the conclusion that a benzofluorene derivative may be responsible for forming the 'unknown' chemical-DNA adduct. Comparative in vitro and in vivo studies on the adducting properties of all three isomers of benzofluorene indicated that 7H-benzo[c]fluorene is responsible for producing the 'unknown' adduct observed in the lung of mice ingesting coal tar. Animal feeding studies also demonstrated that 7H-benzo[c]fluorene formed considerably more lung DNA adducts than 11H-benzo[a]fluorene and 11H-benzo[b]fluorene. These data indicate that the four-ring polycyclic aromatic hydrocarbon 7H-benzo[c]fluorene, a hydrocarbon not previously shown to form DNA adducts in lung, is in fact a potent lung DNA adductor and is a candidate PAH for causing lung tumors in animals treated with coal tar.

Sensitivity to tropospheric ozone is highly variable in cultivars of different plant species. Wheat, an important cereal crop, has been found to be sensitive to elevated ozone levels leading to differences in grain yields. The objective of this study was to compare the effects of elevated tropospheric ozone on growth, yield and nutritional quality of two species of wheat, Triticum aestivum (PBW 343) and Triticum durum (HD 2936), which are tropical wheat cultivars commonly grown in northern India. Experiments were conducted growing winter wheat (rabi season) under elevated tropospheric ozone in northern India for two years in open-top chambers (OTCs) under charcoal-filtered air (CF), non-filtered air (NF), open air (OA) and elevated ozone (EO) concentration (NF + 25-35 ppb O 3 ). There were different species responses to EO, with the modern aestivum wheat cultivar being more sensitive than durum wheat. The declines in all growth and yield parameters were greater in T. aestivum than T. durum in both the years. On average there was a 7% greater reduction in the photosynthetic rate and stomatal conductance in T. aestivum as compared to T. durum under EO at the flowering stage, and a 6% more reduction in leaf chlorophyll was observed on T. aestivum as compared to T. durum. Exposure to elevated O 3 caused a decrease in the number of leaves and leaf area index, rubisco enzyme activity and chlorophyll in both the species. More reductions in grain yield were observed in T. aestivum (15 and 19%) as compared to T. durum (9 and 13%) under EO in the two years, respectively. Filtration of air significantly increased all growth and yield parameters in both species of wheat.

No abstract

No abstract

7H-Benzo[c]fluorene (benzo[c]fluorene) is a major DNA adduct forming component of coal tar in lung of mice. The present study evaluated the types of PAH:DNA adducts formed from different neat coal tar samples and soils contaminated with coal tar. Mice were fed diets containing coal tar either neat or as a contaminant in an environmental soil sample for 14 days, and the types of chemical:DNA adducts formed in lung were evaluated using 32P-postlabeling and HPLC analysis. Three major DNA adducts derived respectively from benzo[b]fluoranthene (B[b]F), benzo[a]pyrene (B[a]P), and benzo[c]fluorene were detected in three of the four neat coal tar samples evaluated. In contrast, only a single major DNA adduct derived from benzo[c]fluorene was observed with the remaining tar sample. Ingestion of coal tar contaminated soil resulted in DNA adducts primarily derived from benzo[c]fluorene and B[b]F; a B[a]P derived DNA adduct was not detected. The DNA adducts derived from benzo[c]fluorene and B[b]F but not B[a]P were also observed with animals fed methylene chloride extracts of three of these soils but not the one designated A1000H soil. However, the extract of A1000H resulted in a B[a]P:DNA adduct being detected along with adducts formed from B[b]F and benzo[c]fluorene. The selective formation of the benzo[c]fluorene:DNA adduct with coal tar contaminated soils indicates that the in vivo systemic bioavailability and/or metabolism of benzo[c]fluorene is relatively high when compared to other DNA adducting hydrocarbons within coal tar. Benzo[c]fluorene may play a critical role in the potential of contaminated soil to induce a toxicological response in animals.