Safety with access scaffolds: development of a prototype decision aid based on accident analysis

PROBLEM: Accidents involving temporary access systems, particularly temporary scaffolds, account for a large proportion of injuries in the construction industry worldwide. METHOD: This paper outlines the development of a prototype decision aid (SCAFPASS, an abbreviation for Scaffold Planning Aid for System Safety) to promote access scaffold safety. It was guided by an examination of the root-causes and management deficiencies apparent in: (a) paper-based files of 186 access-related incidents held by the Health and Safety Executive (HSE) in the UK; and (b) computer-based files of 2,910 incidents appearing in the HSE database between 1997 to 2000. RESULTS: The more frequent root-causes included the fitting of defective components, unauthorized modification of the structure, omission of barriers, and errors resulting in simple, readily detectable structural faults. Common managerial deficiencies included failure to control risk, unsafe methods and procedures, and inadequate training and supervision. IMPACT ON INDUSTRY: SCAFPASS aims to avoid these root-causes by improving safety management from the outset and throughout all phases of a project.     

ACUTE TOXICITY OF PICRIC ACID AND PICRAMIC ACID TO RAINBOW TROUT,SALMO GAIRDNERI,AND AMERICAN OYSTER,CRASSOSTREA VIRGINICA1

ABSTRACT Picric acid (2,4,6-trinitrophenol) and picramic acid (2-amino-4,6-dinitrophenol) are potential water pollutents due to a variety of industrial and munition uses. The possible impacts of picric and picramic acid to two recreationally and commercially important species, rainbow trout, Salmo gairdneri, and American oysters, Crassostrea virginica, were evaluated. Picramic acid was more toxic than picric acid to both species tested. The 96-h LC50s for picric and picramic acids for rainbow trout were 109.6 and 46.2 mg/1, respectively. The 144-h LC50s for picric and picramic acid for American oysters were 254.9 and 69.8 mg/1, respectively. Sublethal no growth EC50s and shell deposition EC50s for oysters showed that both compounds caused adverse effects at much lower concentrations than indicated by the LC50s. For example, the 144-h shell deposition EC50s were 27.9 mg/1 for picric acid and 5.6 mg/1 for picramic acid. Sediment adsorbtion studies in estuarine water indicated that both compounds are not readily adsorbed which suggests that sediment would not play a major role as a sink in contaminated systems. Oysters, which filter large quantities of particulate matter, would more likely be affected by picric and picramic acids in the water column than by exposure to contaminated sediment.     

Investigation of insecticide leaching from potted nursery stock and aquatic health benefits of bioretention cells receiving nursery runoff

Tree nurseries and greenhouses within the USDA red imported fire ant (RIFA) quarantine zone are required to incorporate insecticides into their potting media to prevent artificial spread of RIFA. Bifenthrin and fipronil are two common insecticides that are incorporated into potting media. During irrigation and stormwater events, there is potential for insecticides to leach from nursery pots, resulting in the contamination of nearby surface waters. In this study, occurrences of insecticides in simulated nursery runoff were compared with two irrigation strategies and two types of containers in single pot leaching and field runoff simulations. In addition, toxicity of pot leachate to the aquatic invertebrate, Hyallela azteca, was measured, and removal efficiencies of insecticides from bioretention cell media were evaluated. Overhead irrigation resulted in significantly higher concentrations than drip irrigation, and RootMaker® pots allowed more leaching as compared to standard slick-wall pots. However, in all tests, the average concentration of bifenthrin during 15 days of leaching in both pot and field simulations was greater than 200 ng/L; more than 100-fold greater than the LC₅₀ for H. azteca. Toxicity studies confirmed this level of toxicity. Higher amounts of compost, 20 and 40 %, in bioretention cell media resulted in greater percent reduction of both bifenthrin and fipronil. This study determined that management techniques may be able to limit the amount of insecticide that leaches from pots and runs off to receiving water bodies. Specifically, the selection of appropriate pot types, irrigation strategies, or filtering runoff through bioretention cells may reduce contamination loads. Thus, further best management strategies such as the use of bioretention cells are needed in nursery and greenhouse facilities to prevent surface water runoff from transporting toxic insecticides.     

Mercury Mass Balances: A Case Study of Two North Dakota Power Plants

ABSTRACT

The Energy & Environmental Research Center (EERC) conducted a mercury-sampling program to provide data on the quantity and forms of Hg emitted and on the Hg removal efficiency of the existing air pollution control devices at two North Dakota power plants—Milton R. Young Station and Coal Creek Station. Minnkota Power Cooperative, Great River Energy, the North Dakota Industrial Commission, and EPRI funded the project. The primary objective was to obtain accurate measurements of Hg released from each plant, as verified by a material balance. A secondary objective was to evaluate the ability of a mercury continuous emission monitor (CEM) to measure total Hg at the stack.

At both plants, speciated Hg measurements were made at the inlets and outlets of both the electrostatic precipi-tators (ESPs) and the flue gas desulfurization (FGD) systems. A Semtech Hg 2000 (Semtech Metallurgy AB) mercury CEM was used to measure the total Hg emissions at the stack in real time. Using these measurements and plant data, the measured Hg concentrations in the coal, FGD slurries, and ESP ash, a Hg mass flow rate was calculated at each sampling location. Excellent Hg mass balances were obtained (±15%). It was also found that the Hg was mostly in the elemental phase (~90%), and the small amount of oxidized Hg that was generated was removed by the FGD systems.

Insignificant amounts of particulate-bound Hg were measured at both plants. However, 10-20% of the elemental Hg measured prior to the ESP was converted to oxidized Hg across the ESP. The data show that, at these facilities, almost all of the Hg generated is being emitted into the atmosphere as elemental Hg. Local or regional deposition of the Hg emitted from these plants is not a concern. However, the Hg does become part of the global Hg burden in the atmosphere. Also, the evidence appears to indicate that elemental Hg is more difficult to remove from flue gas than oxidized Hg is.     

Atrazine effects on in vitro maturation and in vitro fertilization in the bovine oocyte

The effect of low levels of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) on in vitro oocyte maturation, in vitro capacitation of sperm, or in vitro fertilization of bovine oocytes and on the quality of blastocyst formation was studied. Bovine oocytes collected from abattoir ovaries were matured, fertilized, and developed to the blastocyst stage in vitro. Embryos that reached a morula or blastocyst stage were stained with Hoechst 33258 stain to determine the number of blastomeres per embryo. Three bulls whose fertilization rates were proven consistent among straws were used for this study. Atrazine was tested at concentrations of 0.01, 0.1, 1, and 10 microM in either the maturation medium, sperm capacitation medium, or the fertilization medium. Because atrazine was dissolved in ethanol, an ethanol control was used to determine any possible effects of ethanol on the in vitro process. The addition of atrazine to both the maturation and fertilization media did not result in any significant difference in fertilization rates between the controls and the treatments. In the capacitation medium, a significant difference between the controls and the atrazine levels of 0.1, 1, and 10 microM was noted for one bull. Atrazine did not affect the number of blastomeres per embryo. There was not a significant difference (p>0.05) in the number of blastomeres per embryo between the controls and the different levels of atrazine in each medium. This study indicates that low levels of atrazine do not have an effect on in vitro fertilization rates or the number of blastomeres per embryo produced in vitro.     

Petroleum biodegradation in soil: The effect of direct application of surfactants

The direct application of surfactants to petroleum-contaminated soil has been proposed as a mechanism to increase the bioavailability of insoluble compounds. Solubilization of hydrophobic compounds into the aqueous phase appears to be a significant rate limiting factor in petroleum biodegradation in soil. Nonionic surfactants have been developed to solubilize a variety of compounds, thus increasing the desorption of contaminants from the soil. In this study, laboratory scale land treatment scenarios were used to monitor the bioremediation of petroleum contaminated soils. In efforts to achieve the lowest levels of residual petroleum hydrocarbons in the soil following biotreatment, 0.5 and 1.0% (volume/weight) surfactant was blended into soils under treatment. Two soil types were studied, a high clay content soil and a sandy, silty soil. In both cases, the addition of surfactant (Adsee 799®, a blend of ethoxylated fatty acids, Witco Corporation) stimulated biological activity as indicated by increased heterotropbic colony forming units per gram of soil. However, the increased activity was not correlated with removal of petroleum hydrocarbons. The results suggest that the application of surfactants directly to the soil for the purpose of solubilizing hydropbobic compounds was not successful in achieving greater levels of petroleum hydrocarbon removal.     

THE INFLUENCE OF SPRING AND FALL TEMPERATURES ON THE AVOIDANCE RESPONSE OF JUVENILE ATLANTIC MENHADEN,BREVOORTIA TYRANNUS,EXPOSED TO SIMULTANEOUS CHLORINE-δT CONDITIONS1

ABSTRACT: The avoidance response of groups of juvenile Atlantic menhaden, Brevoortia tyrannus, was evaluated by exposing test species to a range of simultaneous total residual chlorine (TRC) (0.00, 0.05, 0.10, and 0.15 mg/L) and elevated temperature (0, 2, 4, and 6°C) conditions simulating power plant discharges. This species was tested at both 15 and 20°C to determine possible effects of acclimation temperature on the avoidance response. These temperatures were selected to represent spring or fall thermal conditions when most East Coast power plant facilities initiate power plant chlorination in the spring or terminate the use of this biocide in the fall. An unbalanced 3-factor factorial design was used to develop response surface avoidance models at 15 and 20°C. The model developed at 15°C showed: (1) an increase in avoidance occurred at all δT conditions as TRC increased from 0.00 to 0.05 mg/L; (2) a greater degree of avoidance occured at TRC concentrations above 0.05 mg/L at all δT conditions; and (3) TRC was the most important term inflencing avoidance. The model for Atlantic menhaden at 20°C showed: 1) avoidance increased with increasing TRC concentration at each δT condition; (2) avoidance did not necessarily increase with increasing δT's at each TRC concentration; (3) greatest avoidance occured at 0°C δT and 0.15 mg/L TRC; and (4) TRC was the most important term influencing avoidance. There was a significant difference (p < 0.00001) between avoidance models at 15 and 20°C. However, when extreme conditions of 0.15 mg/L TRC and 0–6°δT were compared, the degree of avoidance responses (percent time in control area) was similar.     

Mercury mass balances: a case study of two North Dakota power plants

The Energy & Environmental Research Center (EERC) conducted a mercury-sampling program to provide data on the quantity and forms of Hg emitted and on the Hg removal efficiency of the existing air pollution control devices at two North Dakota power plants--Milton R. Young Station and Coal Creek Station. Minnkota Power Cooperative, Great River Energy, the North Dakota Industrial Commission, and EPRI funded the project. The primary objective was to obtain accurate measurements of Hg released from each plant, as verified by a material balance. A secondary objective was to evaluate the ability of a mercury continuous emission monitor (CEM) to measure total Hg at the stack. At both plants, speciated Hg measurements were made at the inlets and outlets of both the electrostatic precipitators (ESPs) and the flue gas desulfurization (FGD) systems. A Semtech Hg 2000 (Semtech Metallurgy AB) mercury CEM was used to measure the total Hg emissions at the stack in real time. Using these measurements and plant data, the measured Hg concentrations in the coal, FGD slurries, and ESP ash, a Hg mass flow rate was calculated at each sampling location. Excellent Hg mass balances were obtained (+/- 15%). It was also found that the Hg was mostly in the elemental phase (approximately 90%), and the small amount of oxidized Hg that was generated was removed by the FGD systems. Insignificant amounts of particulate-bound Hg were measured at both plants. However, 10-20% of the elemental Hg measured prior to the ESP was converted to oxidized Hg across the ESP. The data show that, at these facilities, almost all of the Hg generated is being emitted into the atmosphere as elemental Hg. Local or regional deposition of the Hg emitted from these plants is not a concern. However, the Hg does become part of the global Hg burden in the atmosphere. Also, the evidence appears to indicate that elemental Hg is more difficult to remove from flue gas than oxidized Hg is.     

Assessment of animal impacts on bacterial water quality in a South Carolina, USA tidal creek system

Fecal pollution may adversely impact water quality in coastal ecosystems. The goal of this study was to determine whether cattle were a source of fecal pollution in a South Carolina watershed. Surface water samples were collected in June 2002 and February through March 2003 in closed shellfish harvesting waters of Toogoodoo Creek in Charleston County, SC. Fecal coliform concentrations in 70 % of the water samples taken for this study exceeded shellfish harvesting water standards. Ribotyping was performed in order to identify animal sources contributing to elevated fecal coliform levels. Escherichia coli isolates (n?=?253) from surface water samples were ribotyped and compared to a ribotype library developed from known sources of fecal material. Ribotypes from water samples that matched library ribotypes with 90 % maximum similarity or better were assigned to that source. Less than half of the unknown isolates (38 %) matched with library isolates. About half (53 %) of the matched ribotypes were assigned to cattle isolates and 43 % to raccoon. Ribotyping almost exclusively identified animal sources. While these results indicate that runoff from cattle farms was a likely source of fecal pollution in the watershed, wildlife also contributed. Given the small size of the library, ribotyping was moderately useful for determining the impact of adjacent cattle farms on Toogoodoo Creek. Increasing the number and diversity of the wildlife sources from the area would likely increase the usefulness of the method.     

Mitochondrial and nuclear DNA analysis of population subdivision among young-of-the-year Spanish mackerel (Scomberomorus maculatus) from the western Atlantic and Gulf of Mexico

The degree of population subdivision among collections of young-of-the-year (YOY) Spanish mackerel Scomberomorus maculatus sampled from along the Atlantic coast of the United States (Atlantic) and Gulf of Mexico (Gulf) was examined. Young-of-the-year were collected from spawning areas to minimize possible mixing among putative spawning stocks that may occur at later life history stages along migratory pathways or at over-wintering grounds. Restriction fragment length polymorphism (RFLP) analysis of the mitochondrial DNA (mtDNA) ND4 region and a nuclear actin intron was conducted. Collections in each of two years were analyzed to minimize bias associated with sampling at a single point in space or time. Substantial variation was detected at ND4 (haplotype diversity=0.81) and at the actin intron locus (gene diversity=0.21). Significant differences in gene diversity or allele frequencies were not detected among temporal samples at any of three locations. A homogeneous distribution of genetic variance among samples from widely spaced geographic regions was consistent with the hypothesis that Spanish mackerel comprise a single intermingling genetic stock. Power analysis showed that the mitochondrial analysis from this study was much more likely to detect population subdivision than analysis of the nuclear actin locus, despite lower mtDNA sample size. Received: 3 January 2000 / Accepted: 28 August 2000