Toxicity assessment of sediments from the Grand Calumet River and Indiana Harbor Canal in Northwestern Indiana, USA.

The objective of this study was to evaluate the toxicity of sediments from the Grand Calumet River and Indiana Harbor Canal located in northwestern Indiana, USA. Toxicity tests used in this assessment included 10-day sediment exposures with the amphipod Hyalella azteca, 31-day sediment exposures with the oligochaete Lumbriculus variegatus, and the Microtox Solid-Phase Sediment Toxicity Test. A total of 30 sampling stations were selected in locations that had limited historic matching toxicity and chemistry data. Toxic effects on amphipod survival were observed in 60% of the samples from the assessment area. Results of a toxicity test with oligochaetes indicated that sediments from the assessment area were too toxic to be used in proposed bioaccumulation testing. Measurement of amphipod length after the 10-day exposures did not provide useful information beyond that provided by the survival endpoint. Seven of the 15 samples that were identified as toxic in the amphipod tests were not identified as toxic in the Microtox test, indicating that the 10-day H. azteca test was more sensitive than the Microtox test. Samples that were toxic tended to have the highest concentrations of metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). The toxic samples often had an excess of simultaneously extracted metals (SEM) relative to acid volatile sulfide (AVS) and had multiple exceedances of probable effect concentrations (PECs). Metals may have contributed to the toxicity of samples that had both an excess molar concentration of SEM relative to AVS and elevated concentrations of metals in pore water. However, of the samples that had an excess of SEM relative to AVS, only 38% of these samples had elevated concentration of metals in pore water. The lack of correspondence between SEM-AVS and pore water metals indicates that there are variables in addition to AVS controlling the concentrations of metals in pore water. A mean PEC quotient of 3.4 (based on concentrations of metals, PAHs, and PCBs) was exceeded in 33% of the sediment samples and a mean quotient of 0.63 was exceeded in 70% of the thirty sediment samples from the assessment area. A 50% incidence of toxicity has been previously reported in a database for sediment tests with H. azteca at a mean quotient of 3.4 in 10-day exposures and at a mean quotient of 0.63 in 28-day exposures. Among the Indiana Harbor samples, most of the samples with a mean PEC quotient above 0.63 ( i.e., 15 of 21; 71%) and above 3.4 ( i.e., 10 of 10; 100%) were toxic to amphipods. Results of this study and previous studies demonstrate that sediments from this assessment area are among the most contaminated and toxic that have ever been reported.

Bacterial retention properties of heat and moisture exchange filters.

We have examined the properties of six heat and moisture exchange filters (HMEF) to ascertain their resistance to liquid flow and their ability to retain a challenge bacterium, Pseudomonas diminuta, from aqueous and nebulized suspensions. Only one HMEF, the Pall Ultipor was able to withstand a significantly greater pressure of liquid than that found in clinical practice. However, when breached, the HMEF were unable to prevent transmission of micro-organisms from aqueous suspension. Only the Darex Hydrobac filter failed to meet the manufacturer's claim for filter efficiency for nebulized bacteria, mainly because the filter housing failed under test. When the reduction in bacterial cells after passage of the nebulized Pseudomonas diminuta through the HMEFs was analysed statistically, the data showed that the HMEF produced by Pall (Ultipor) and Intersurgical (Filter therm) were superior to those produced by DAR Mediplan (Hygrobac), Intertech (HME 225-2835-800) and Gibeck (Humid-vent).

A comparative evaluation of liquid antacids commercially available in the United Kingdom.

Twenty-six liquid antacids have been assessed using a procedure which permits comparisons to be made in terms of 'antacid efficiency' parameter which reflects both the ability to maintain pH above 3 and the duration of the effect. A wide variation in activity was demonstrated in the preparations tested and it was concluded that antacids could be classified into four categories according to potency.