Abstract

  The San Francisco Bay was the subject of studies by NOAA and EPA in 2000 and by NOAA in 2001. In each year, 99 sediment samples distributed within strata over the entire Bay were collected and analyzed for a range of chemical and biological parameters. A biomarker assay, P450 Human Reporter Gene System (EPA Method 4425), was used to document the occurrence and distribution of CYP1A1-inducing compounds in these samples. The assay utilizes a stably transfected human hepatoma cell line with a plasmid containing the firefly luciferase gene downstream of CYP1A1 promoter sequences. When these cells are exposed to CYP1A1-inducing compounds (PAHs, PCBs, and dioxins/furans), luciferase is produced, and can be easily measured with a luminometer. The responses, expressed as mg of benzo[a]pyrene equivalents/g (B[a]PEq) from samples collected in 2000 and 2001 were quite similar (means = 21.2, 19.9; upper 99% confidence limits = 28.0, 26.9). Each year 5 stations were over 60 mg/g B[a]PEq, and the numbers of samples above the upper confidence limit were 20 and 17. The PAHs were most highly correlated with the 4425 responses (R2 values = 0.64, 0.63). At several of the stations, but not all, a high 4425 response was observed when there was a significant reduction in normal development of sea urchin embryos. In 2000, splits of extracts were first cleaned of PAHs by silica gel before 4425 testing and the results compared to high-resolution GC/MS analyses of dioxins, furans, and PCBs of 63 samples. Most samples were less than the HRGS reporting limit of 10 ng/Kg TEQ, which was confirmed GC/MS and only one sample was significantly higher by GC/MS. Method 4425 is an inexpensive and rapid screening tool for determining which of the numerous sediment locations sampled contain significant levels of carcinogenic and toxic compounds, and are therefore likely to exhibit degraded biological communities.