eight sites were sampled during seven rain events to quantify and identify the sources ofpolycyclic aromatic hydrocarbons in urban runoff in the city of tijuana, mexico. the total σ16 pahsconcentration rangedfrom 1113 to 4866 μg/lin the sampled sites and thetotal suspended solid concentrations ranged from 7725 to 4413 μg/l. the high concentrations of total suspended solids were probably the res...

When a study outcome is rare in all strata used for an analysis, the odds ratio estimate of causal effects will approximate the risk ratio; therefore, odds ratios from most case-control studies can be interpreted as risk ratios. However, if a study outcome is common, the odds ratio will be further from 1 than the risk ratio. There is debate regarding the merits of risk ratios compared with odds...