An assessment of the toxicity of phthalate esters to freshwater benthos. 1. Aqueous exposures.

Tests were performed with the freshwater invertebrates Hyalella azteca, Chironomus tentans, and Lumbriculus variegatus to determine the acute toxicity of six phthalate esters, including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBP), di-n-hexyl phthalate (DHP), and di-2-ethylhexyl phthalate (DEHP). It was possible to derive 10-d LC50 (lethal concentration for 50% of the population) values only for the four lower molecular weight esters (DMP, DEP, DBP, and BBP), for which toxicity increased with increasing octanol-water partition coefficient (Kow) and decreasing water solubility. The LC50 values for DMP, DEP, DBP, and BBP were 28.1, 4.21, 0.63, and 0.46 mg/L for H. azteca; 68.2, 31.0, 2.64, and > 1.76 mg/L for C. tentans; and 246, 102, 2.48, and 1.23 mg/L for L. variegatus, respectively. No significant survival reductions were observed when the three species were exposed to either DHP or DEHP at concentrations approximating their water solubilities.

An assessment of the toxicity of phthalate esters to freshwater benthos. 2. Sediment exposures.

Seven phthalate esters were evaluated for their 10-d toxicity to the freshwater invertebrates Hyalella azteca and Chironomus tentans in sediment. The esters were diethyl phthalate (DEP), di-n-butyl phthalate (DBP), di-n-hexyl phthalate (DHP), di-(2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), and a commercial mixture of C7, C9, and C11 isophthalate esters (711P). All seven esters were tested in a sediment containing 4.80% total organic carbon (TOC), and DBP alone was tested in two additional sediments with 2.45 and 14.1% TOC. Sediment spiking concentrations for DEP and DBP were based on LC50 (lethal concentration for 50% of the population) values from water-only toxicity tests, sediment organic carbon concentration, and equilibrium partitioning (EqP) theory. The five higher molecular weight phthalate esters (DHP, DEHP, DINP, DIDP, 711P), two of which were tested and found to be nontoxic in water-only tests (i.e., DHP and DEHP), were tested at single concentrations between 2,100 and 3,200 mg/kg dry weight. Preliminary spiking studies were performed to assess phthalate ester stability under test conditions. The five higher molecular weight phthalate esters in sediment had no effect on survival or growth of either C. tentans or H. azteca, consistent with predictions based on water-only tests and EqP theory. The 10-d LC50 values for DBP and H. azteca were >17,400, >29,500, and >71,900 mg/kg dry weight for the low, medium, and high TOC sediments, respectively. These values are more than 30x greater than predicted by EqP theory and may reflect the fact that H. azteca is an epibenthic species and not an obligative burrower. The 10-d LC50 values for DBP and C. tentans were 826, 1,664, and 4.730 mg/kg dry weight for the low, medium, and high TOC sediments, respectively. These values are within a factor of two of the values predicted by EqP theory. Pore-water 10-d LC50 values for DBP (dissolved fraction) and C. tentans in the three sediments were 0.65, 0.89, and 0.66 of the water-only LC50 value of 2.64 mg/L, thereby agreeing with EqP theory predictions to within a factor of 1.5. The LC50 value for DEP and C. tentans was >3,100 mg/kg dry weight, which is approximately 10x that predicted by EqP theory. It is postulated that test chemical loss and reduced organism exposure to pore water may have accounted for the observed discrepancies with EqP calculations for DEP

Evaluation of surgical scrub and antiseptic solutions for surgical preparation of canine paws.

The purpose of the prospective study reported here was to evaluate surgical preparation of canine paws. Three combinations of surgical scrub solutions and antiseptic solutions were used: (1) 7.5% povidone-iodine scrub/10% povidone-iodine solution; (2) 2% chlorhexidine acetate scrub/2% chlorhexidine diacetate solution; and (3) tincture of green soap/70% isopropyl alcohol. The control was warm (38 to 42 C) tap water. Four microbial colony counts were used to evaluate surgical preparation of 4 paws of 8 dogs. Specimens were obtained from the paws for a baseline microbial flora count. After surgical scrub was performed, additional specimens were obtained for bacteriologic culturing. Antiseptic was applied followed by collection of another specimen for bacteriologic culturing. A final specimen was obtained following a 24-hour period under a sterile occlusive bandage. The 3 scrub solutions and the tap water control resulted in lower colony counts following scrubbing of the paws; however, only the 3 antiseptic solutions resulted in further colony count reduction after their application. Evaluation of residual colony counts isolated from specimens taken after a 24-hour period under a sterile occlusive bandage revealed chlorhexidine and povidone-iodine scrub/antiseptic combinations to be similar in antibacterial activity, with significantly (P less than or equal to 0.05) lower colony counts than those from specimens of paws treated with either the tincture of green soap/isopropyl alcohol combination or the tap water control. The lack of a significant difference between the bacterial counts immediately after surgical preparation with povidone-iodine and chlorhexidine and their respective 24-hour residual counts, indicated no particular advantage to surgical preparation and occlusive bandaging 24 hours prior to surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute and embryo-larval toxicity of phenolic compounds to aquatic biota.

Because of the prevalence of phenolic compounds in various types of effluents, both acute and embryo-larval bioassays were performed on eight phenolic compounds with rainbow trout, fathead minnows and Daphnia pulicaria. In flow-through bioassays, the 96-hr LC50 values for rainbow trout and fathead minnows ranged from < 0.1 mg/L for hydroquinone to > 100 mg/L for resorcinol. Daphnia pulicaria was consistently the least sensitive species tested as measured in 48-hr bioassays, while fathead minnows and rainbow trout varied in their relative sensitivity to phenolics as measured in 96-hr tests. Fathead minnows were more sensitive to phenol at 25 degrees C than at 14 degrees C. In embryo-larval bioassays with phenol, fathead minnow growth was significantly reduced by 2.5 mg/L phenol, while rainbow trout growth was significantly reduced by 0.20 mg/L phenol. For both species the embryo-larval effects concentration was 1.1% of the 96-hr LC50. Another embryo-larval bioassay was attempted with p-benzoquinone, a highly toxic phenolic compound found in fossil fuel processing wastewaters, which was discontinued because the compound was rapidly degraded chemically or biologically in the headtank and aquaria.