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We have studied the rate constants for the reaction of O ϩ with N 2 over the temperature range 300-1600 K and the reaction of O ϩ with O 2 over the range 300 to 1800 K. The results are in good agreement with previous measurements made up to 900 K. The rate constant for the O ϩ reaction with N 2 shows a minimum in the temperature range 1100-1300 K. The increase above this temperature is due to N 2 vϭ2 becoming populated. The rate constant for O ϩ ϩO 2 shows a minimum in the 800-1100 K range. Comparing to previous drift tube measurements allows the rate constant for O 2 ͑vϾ0͒ to be derived. The vϾ0 rate constant is approximately five times larger than the vϭ0 rate constant.

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Seven animal drugs [penicillin G (PENG), sulfadimethoxine (SDMX), oxytetracycline (OTET), erythromycin (ERY), ketoprofen (KETO), thiabendazole (THIA), and ivermectin (IVR)] were used to evaluate the drug distribution between milk fat and skim milk fractions of cow milk. More than 90% of the radioactivity was distributed into the skim milk fraction for ERY, KETO, OTET, PENG, and SDMX, approximately 80% for THIA, and 13% for IVR. The distribution of drug between milk fat and skim milk fractions was significantly correlated to the drug's lipophilicity (partition coefficient, log P, or distribution coefficient, log D, which includes ionization). Data were fit with linear mixed effects models; the best fit was obtained within this data set with log D versus observed drug distribution ratios. These candidate empirical models serve for assisting to predict the distribution and concentration of these drugs in a variety of milk and milk products.

It is important to understand the partitioning of drugs in processed milk and milk products, when drugs are present in raw milk, in order to estimate the potential consumer exposure. Radioisotopically labeled erythromycin, ivermectin, ketoprofen, oxytetracycline, penicillin G, sulfadimethoxine, and thiabendazole were used to evaluate the distribution of animal drugs among rennet curd, whey, and protein fractions from skim cow milk. Our previous work reported the distribution of these same drugs between skim and fat fractions of milk. Drug distribution between curd and whey was significantly correlated (R = 0.70) to the drug's lipophilicity (log P), with improved correlation using log D (R = 0.95). Distribution of drugs was concentration independent over the range tested (20-2000 nM). With the exception of thiabendazole and ivermectin, more drug was associated with whey protein than casein on a nmol/g protein basis (oxytetracycline experiment not performed). These results provide insights into the distribution of animal drug residues, if present in cow milk, among milk fractions, with possible extrapolation to milk products.

Model results indicated that the mean WWTP influent concentration of NoV GII (3.9 log 10 gc/liter; 95% credible interval [CI], 3.5, 4.3 log 10 gc/liter) is larger than the value for NoV GI (1.5 log 10 gc/liter; 95% CI, 0.4, 2.4 log 10 gc/liter), with large variations occurring from one WWTP to another. For WWTPs with mechanical systems and chlorine disinfection, mean log 10 reductions were ؊2.4 log 10 gc/liter (95% CI, ؊3.9, ؊1.1 log 10 gc/liter) for NoV GI, ؊2.7 log 10 gc/liter (95% CI, ؊3.6, ؊1.9 log 10 gc/liter) for NoV GII, and ؊2.9 log 10 PFU per liter (95% CI, ؊3.4, ؊2.4 log 10 PFU per liter) for MSCs. Comparable values for WWTPs with lagoon systems and chlorine disinfection were ؊1.4 log 10 gc/liter (95% CI, ؊3.3, 0.5 log 10 gc/liter) for NoV GI, ؊1.7 log 10 gc/liter (95% CI, ؊3.1, ؊0.3 log 10 gc/liter) for NoV GII, and ؊3.6 log 10 PFU per liter (95% CI, ؊4.8, ؊2.4 PFU per liter) for MSCs. Within WWTPs, correlations exist between mean NoV GI and NoV GII influent concentrations and between the mean log 10 reduction in NoV GII and the mean log 10 reduction in MSCs.H uman norovirus (NoV) is the leading cause of food-associated gastroenteritis in the United States (1) and Canada (2). U.S. residents are estimated to experience five episodes of norovirus gastroenteritis in their lifetimes (3). NoV is primarily spread via the fecal-oral route. However, attribution of a particular case of NoV illness to a specific source is complex. The transmission may be direct (person to person) or indirect (via contact with contaminated fomites) or may occur through the ingestion of contaminated food or water (4). Noroviruses are genetically diverse, comprising six genogroups (5), three of which (genogroup I [GI], GII, and GIV) are capable of causing illness in humans (6).Among foodborne NoV outbreaks, bivalve molluscs (e.g., clams, oysters, mussels), leafy vegetables, and fruits are the most frequently implicated (7). More than half of the norovirus outbreaks attributed to the consumption of bivalve molluscs in the United States during the years from 2001 to 2008 are believed to have originated from contamination during production or processing (7). Bivalve molluscan shellfish typically grow in estuaries, which may contain NoV-contaminated human fecal material from municipal wastewater outfalls, combined sewer overflow, or nonpoint sources of pollution, including human waste discharged from marine vessels (8, 9). Bivalve molluscan shellfish feed on algae from the surrounding water. During this feeding process, each bivalve mollusc may filter 20 to 90 liters of water per day and bioaccumulate a variety of microorganisms, including viruses and bacteria that are associated with pollution sources (8,(10)(11)(12). Significantly, molluscan shellfish have been found to retain viruses to a greater extent and for much longer periods than they do bacteria (8,13,14). Bivalve molluscs, therefore, may become contaminated with NoV when they are grown in harvesting areas contaminated with human wastes.In the United States and in Canada, ar...