Bridge Painting Research Articles

Assessment of lead exposure controls on bridge painting projects using worker blood lead levels

A retrospective analysis of worker blood lead levels (BLL) was conducted using blood lead data collected by four bridge painting contractors before and after lead exposure. The objective of the study was to evaluate the effectiveness of exposure controls in preventing elevated blood lead levels (>25 μg/dl) during bridge painting projects. The contractors selected for the study submitted BLL data for 289 workers representing ten work tasks and 11 bridge painting projects. In total, 713 blood lead levels results were evaluated.The mean blood lead level for all work classifications combined was 10.9 μg/dl at baseline compared with 14.9 μg/dl after two months of exposure and 15.0 μg/dl after four months of exposure. Two months after initial exposure, 29% of the painters and 35% of the laborers had a 10 μg/dl incremental increase or greater in blood lead level. Likewise, 18% of the painters and 26% of the laborers had a blood lead level greater than 25 μg/dl during the same time. The blood lead levels that exceeded the 25 μg/dL threshold ranged from 30μg/dL-63 μg/dL for painters and 26 μg–56 μg/dL for laborers.All work tasks with high-intensity exposure (abrasive blaster/painter, abrasive blaster, painter & laborer) experienced an average blood lead level increase that ranged from 0.2 μg/dl to 8.9 μg/dl two months after initial exposure. Blood lead testing conducted after modified exposure controls (two months after the initial follow-up blood testing) were implemented showed a decrease in average blood lead levels (range −0.14 μg/dl to −2.7 μg/dl) for two high-intensity exposure work tasks. In comparison, the other two high-intensity work tasks had moderate increases (range 1 μg/dl to 2.4 μg/dl). The modified exposure controls included an increase in the air velocity inside of the work containment and an administrative control in the form of additional worker training on lead exposure prevention. The reduction in the 95th percentile (point estimate) BLL exposure profile for each exposure group at the 4-month follow-up blood testing period is associated with modified exposure controls.Ineffective exposure controls were identified through the analysis of worker BLLs. We found two exposure groups (laborer and painter) whose 95th percentile (point estimate) exposure profile was greater than the OSHA construction lead standard's targeted BLL goal (25 μg/dl) during the first two months of exposure. Our research findings provide support for monthly blood lead testing after baseline until blood lead levels are controlled to an acceptable concentration.

Evaluation of the Effectiveness of Hygenall<sup>©</sup> Leadoff<sup>TM</sup> Foaming Soap in Reducing Lead on Workers’ Hands and the Uptake of Lead on Bridge Painting Projects

Although considerable research has been conducted regarding airborne lead exposures during lead paint removal, little data has been collected measuring the lead concentration on workers’ hands in the construction industry. As a result, there are gaps in our understanding of the effectiveness of a standard work practice control (handwashing) in the prevention and control of elevated blood lead levels (BLLs) in the workplace. The primary objective of this study was to assess if a National Institute for Occupational Safety and Health (NIOSH) formulation intended to remove lead from skin (Hygenall© LeadoffTM Foaming Soap) is more effective than a commonly used soap in the industrial painting industry (Zep Cherry Bomb Soap) in reducing the concentration of lead on workers’ hands after exposure. A secondary aim was to assess if using LeadoffTM Foaming Soap during handwashing reduces worker uptake of lead on bridge painting projects. We evaluated hand wipe, air sample and blood lead level data collected by two industrial bridge painting contractors. Airborne exposures ranged from 350 μg/m3 to 19,700 μg/m3. The geometric mean lead concentration remaining on workers’ hands after using Zep Cherry Bomb Soap was 77 μg per hand wipe compared with 61 μg per hand wipe after use of LeadoffTM Foaming Soap for all work classifications. The geometric lead concentration on workers’ hands decreased by 16 μg/hand wipe for all work classifications combined after using LeadoffTM Foaming Soap—a decrease of 21%. The use of Hygenall LeadoffTM Foaming Soap reduced the maximum lead concentration on workers’ hands by 85%. The geometric mean BLL for all work classifications was 12.1 μg/dl before the use of LeadoffTM. After two months of airborne exposure and use of LeadoffTM Foaming Soap at breaks and at the end of the workday, the geometric mean BLL for all work classifications increased to 18.1 μg/dl. Worker BLLs increased despite the reduction in the concentration of lead measured on workers’ hands—most likely a result of ineffective inhalation exposure controls. We found that the LeadoffTM Foaming Soap was more effective in removing lead from workers’ hands than Zep Cherry Bomb.

Evaluation of Lead Exposure by Hand Wipes: A Review of the Effectiveness of Personal Hygiene on Industrial Sites

To evaluate the effectiveness of personal hygiene (handwashing) amongst workers at industrial sites to remove lead from their hands, a retrospective analysis of hand wipe samples was conducted using data collected by two contractors from two bridge painting projects for total lead using method ASTM E-1979-17/EPA SW846 7000B. Exposures resulted from the removal of lead-based paint from the structure and trace elements of lead found in the abrasive blast media. In total, six work tasks were evaluated and sixty unique hand wipe samples were evaluated. Thirty samples were collected during the worker’s lunch break, after they had reportedly washed their hands with a further 30 collected at the end of the workday following the same protocol. To be included in this evaluation, the contractors were required to follow NIOSH Method 9105 (Lead in Dust Wipes-Dermal Surfaces) with subsequent analysis of samples for total lead by an American Industrial Hygiene Association (AIHA) accredited laboratory. All 60 samples contained detectable lead. The lead exposures ranged from 19.5 μg to 3420 μg. The geometric mean for the samples collected was 337 μg. These results indicate that current personal hygiene practices at the evaluated sites are not effective at removing lead from worker’s hands during and after the workday. They also suggest that the residual lead measured on the workers’ hands, at the end of the shift, is likely contributing to the elevated blood lead levels in this population.

Inputs for bridge painting decision support: a synthesis

A bridge paint schedule is a set of treatment types (overcoat, recoat, spot repair) and timings. Age-based or performance-based scheduling decisions for painting steel bridge superstructures are often made using expert opinion, continuation of historical practice or explicit optimisation. Optimisation is the preferred mechanism because it yields solutions that are not only data based but also objective and defensible. The information needed as inputs for optimising painting application decisions (long-term paint scheduling) includes the agency and user costs associated with painting projects and the long-term performance of bridge paint coats or the painted steel component. This paper presents a synthesis of available literature on concepts that have been or could be applied to develop these inputs. The paper also documents the painting decision trees and tables that have been developed in the literature and describes past methodologies that have been used to develop these decision support tools.

Lifecycle Decision Framework for Steel Bridge Painting

Lifecycle Decision Framework for Steel Bridge Painting

Monitoring steel bridge renovation using lead isotopic tracing

Monitoring removal of lead (Pb) paint from steel structures usually involves analysis of environmental samples for total lead and determination of blood Pb levels of employees involved in the Pb paint removal. We used high precision Pb isotopic tracing for a bridge undergoing Pb paint removal to determine if Pb in the environmental and blood samples originated from the bridge paint. The paint system on the bridge consisted of an anti-corrosive red Pb primer top-coated with a Micaceous Iron Oxide (MIO) alkyd. Analysis of the red Pb primer gave uniform isotopic ratios indicative of Pb from the geologically-ancient Broken Hill mines in western New South Wales, Australia. Likewise waste abrasive material, as anticipated, had the same isotopic composition as the paint. The isotopic ratios for other samples lay on 2 separate linear arrays on a207Pb/204Pb versus 206Pb/204Pb diagram, one largely defined by gasoline and the majority of the ambient air data, and the other by data for one sample each of gasoline and ambient air and underwater sediments. Isotopic ratios in background ambient air samples for the project were characteristic of leaded gasoline. Air sampling during paint removal showed a contribution of paint Pb ranging from about 20 to 40%. Isotopic ratios in the blood of 8 employees prior to the commencement of work showed that 6 of these had been previously exposed to the Broken Hill Pb possibly from earlier bridge paint removal projects. One subject appeared to have increased exposure to Pb probably from the paint renovations.

Impact on the environment from steel bridge paint deterioration using lead isotopic tracing, paint compositions and soil deconstruction

Deterioration and repair of lead paint on steel structures can result in contamination of the ambient environment but other sources of lead such as from past use of leaded paint and gasoline and industrial activities can also contribute to the contamination. Using a combination of high precision lead isotopic tracing, detailed paint examination, including with scanning electron microscopy, and soil deconstruction we have compared paint on a steel bridge and bulk soil and lead-rich particles separated from soil. The majority of Pb found in the paint derives from Australian sources but some also has a probable US origin. The isotopic data for the bulk soils and selected particles lie on a mixing line with end members the geologically ancient Broken Hill lead and possible European lead which is suggested to be derived from old lead paint and industrial activities. Data for gasoline-derived particulates lie on this array and probably contribute to soil Pb. Although paint from the bridge can be a source of lead in the soils, isotopic tracing, paint morphology and mineralogical identification indicate that other sources, including from paint, gasoline and industrial activities, are contributing factors to the lead burden. Even though physical characteristics and elemental composition are the same in some particles, the isotopic signatures demonstrate that the sources are different. Plots using 206Pb/208Pb vs 206Pb/207Pb ratios, the common representation these days, do not allow for source discrimination in this investigation.

Metal leaching from the bridge paint waste in the presence of steel grit

The disposal of paint waste from bridge rehabilitation is a significant issue because of the potential release of contaminants and the consequent impact to human health and the environment. In this study, leaching behavior of paint waste was evaluated for 24 bridges in New York State. Although elevated Pb (5–168,090mgkg−1) and other metal concentrations were observed in the paint samples, leaching experiments that included the toxicity characteristic leaching procedure (TCLP) and the multiple extraction procedure (MEP) revealed toxicity characteristic (TC) limits were not exceeded. The relatively low concentrations observed are attributed to the use of iron-based abrasives (steel grit) in the paint removal process. In this research, trace metals are hypothesized to be sequestered through interactions with iron oxide coatings formed on the steel grit surface resulting in reduced leachable concentrations. Through sequential extraction iron oxides were observed at 11.03% by wt and X-ray diffraction (XRD) further corroborated the presence of iron oxide coatings on the steel grit surface. Sequential extraction demonstrated that less than 6.8% of Pb, Cr, and Ba were associated with the exchangeable and carbonate forms, while greater contributions were found with iron oxides. The largest fraction, however, greater than 80%, was associated with the residual phase comprised of minerals in the paint including SiO2 and TiO2.

Comparative study of retrospective methods to reduce non-uniform illumination effects to bridge coating

Abstract Digital image processing methods have been actively studied and applied to various infrastructure components including bridge painting assessment. Despite the advantages of image recognition techniques to bridge coating, the results can be greatly affected by the non-uniform illumination of target conditions. It is necessary to first convert all images to a standardized background illumination condition. The effect caused from non-uniform illumination can be minimized by setting lighting conditions properly or capturing additional calibration images. However, capturing additional calibration images is not possible in many practical situations and hence a good method of shading correction is required. This paper addresses the way to correct digital bridge coating images containing non-uniform illumination, which becomes more difficult when it comes to assessing facility surfaces with rust defects. In order to choose the most appropriate one, four representative shading correction methods were selected and tested to identify their suitability to processing bridge coating images. These methods include: (1) image smoothing, (2) homomorphic filtering, (3) morphological filtering, and (4) entropy minimization method. Test results on bridge coating images showed that the entropy minimization method outperformed the other three methods.

Lifecycle analysis concerning partial deterioration measures of steel bridge painting

Lifecycle analysis concerning partial deterioration measures of steel bridge painting

Occupational Exposure to Organic Solvents during Bridge Painting

Exposure to volatile organic compounds (VOCs) from bridge painting was measured in New York City and New Jersey during the summer and fall seasons from 2005 to 2007. The effect of painting activities (paint coating layer, confinement setup, and application method) and meteorological conditions (temperature, humidity, and wind speed) on solvent exposure to aromatic, ketone, ester, and alkane compounds were individually evaluated. Mixed-effect models were used to examine the combination effects of these factors on the air concentration of total VOCs as the individual compound groups were not present in all samples. Air concentration associated with spraying was not affected by meteorological conditions since spraying was done in a confined space, thus reducing their impact on solvent air concentration. The mixed models for brushing and rolling samples included two fixed factors, i.e. application method and temperature, and one random factor, i.e. sampling day. An independent dataset (daily air samples) was used to validate the mixed model constructed for brushing and rolling samples. The regression line of the predicted values and actual measurements had a slope of 1.32 +/- 0.15 for daily brushing and rolling samples, with almost all points being within the 95% confidence bands. The constructed model provides practical approaches for estimating the solvent exposure from brushing and rolling activities among construction painters. An adjusted mean air concentration derived from the activity-specific spray samples was the best estimate for that painting application.

Personal Exposure, Behavior, and Work Site Conditions as Determinants of Blood Lead Among Bridge Painters

Bridge painters are exposed to lead during several job tasks performed during the workday, such as sanding, scraping, and blasting. After the Occupational Safety and Health Administration standard was passed in 1993 to control lead exposures among construction workers including bridge painters, this study was conducted among 84 bridge painters in the New England area to determine the significant predictors of blood lead levels. Lead was measured in personal air and hand wipe samples that were collected during the 2-week study period and in blood samples that were collected at the beginning and at the end of the study period. The personal air and hand wipe data as well as personal behaviors (i.e., smoking, washing, wearing a respirator) and work site conditions were analyzed as potential determinants of blood lead levels using linear mixed effects models. Our results show that the mean air lead levels over the 2-week period were the most predictive exposure measure of blood lead levels. Other individual-level significant predictors of blood lead levels included months worked on bridge painting crews, education, and personal hygiene index. Of the site-level variables investigated, having a containment facility on site was a significant predictor of blood lead levels. Our results also indicate that hand wipe lead levels were significantly associated with higher blood lead levels at the end of the study period compared with the beginning of the study period. Similarly, smoking on site and respirator fit testing were significantly associated with higher blood lead levels at the end of the study period. This study shows that several individual-level and site-level factors are associated with blood lead levels among bridge painters, including lead exposure through inhalation and possible hand-to-mouth contact, personal behaviors such as smoking on site, respirator fit testing, and work site conditions such as the use of better containment facilities. Accordingly, reduction in blood lead levels among bridge painters can be achieved by improving these workplace practices.

Task-Based Lead Exposures and Work Site Characteristics of Bridge Surface Preparation and Painting Contractors

This study of bridge painters working for small contractors in Massachusetts investigated the causes of elevated blood lead levels and assessed their exposure to lead. Bridge work sites were evaluated for a 2-week period during which personal and area air samples and information on work site characteristics and lead abatement methods were gathered. Short-duration personal inhalable samples collected from 18 tasks had geometric means (GM) of 3 μg/m3 to 7286 μg/m3. Full-shift, time-weighted average (TWA) inhalable samples (⩾6 hours) collected from selected workers and work sites had GMs of 2 μg/m3 to15,704 μg/m3; 80% of samples exceeded the permissible exposure limit (PEL) of 50 μg/m3, on average by a factor of 30. Area inhalable samples collected from three locations ranged from 2 μg/m3 to 40,866 μg/m3 from inside the containment, 2 μg/m3 to 471 μg/m3 from a distance of <6 meters, and 2 μg/m3 to 121 μg/m3 from >6 meters from the containment. Seventy nine percent of the area samples from inside the containment exceeded the PEL on average by a factor of 140. Through observations of work site characteristics, opportunities for improving work methods were identified, particularly the institution of engineering controls (which were only occasionally present) and improvement in the design and construction of the containment structure. The high levels of airborne lead exposures indicate a potential for serious exposure hazard for workers and environmental contamination, which can be mitigated through administrative and engineering controls. Although these data were collected over 10 years ago, a 2005 regulatory review by the Occupational Safety and Health Administration (OSHA) of its lead in construction standard reported that elevated lead exposures and blood lead levels, high occurrence of noncompliance with the lead standard, and nonimplementation of newer technology especially among small painting firms employing <10 workers are still widespread. As a result, the findings of this study are still quite germane even a decade after the introduction of the new OSHA standard.

Skin and Surface Lead Contamination, Hygiene Programs, and Work Practices of Bridge Surface Preparation and Painting Contractors

A 2005 regulatory review of the lead in construction standard by the Occupational Safety and Health Administration (OSHA) noted that alternative pathways of exposure can be as significant as inhalation exposure and that noncompliance with the standard pertaining to hygiene facilities and practices was the second most commonly violated section of the standard. Noncompliance with provisions of the standard and unhealthy work and hygiene practices likely increase the likelihood of take-home lead via contaminated clothing, automobiles, and skin, thus contributing to elevated blood lead levels (BLL) among construction workers and their family members. We performed a cross-sectional study of bridge painters working for small contractors in Massachusetts to investigate causes of persistent elevated BLLs and to assess lead exposures. Thirteen work sites were evaluated for a 2-week period during which surface and skin wipe samples were collected and qualitative information was obtained on personal hygiene practices, decontamination and hand wash facilities, and respiratory protection programs. Results showed lead contamination on workers' skin, respirators, personal automobiles, and the decontamination unit, indicating a significant potential for take-home lead exposure. Overall, the geometric mean (GM) skin lead levels ranged from 373 μg on workers' faces at end of shift to 814 μg on hands at break time. The overall GM lead level inside respirators was 143 μg before work and 286 μg after work. Lead contamination was also present inside workers' personal vehicles as well as on surfaces inside the clean side of the decontamination unit. Review of the respiratory protection programs, work site decontamination and hand wash facilities, and personal hygiene practices indicated that these factors had significant impact on skin and surface contamination levels and identified significant opportunities for improving work site facilities and personal practices. Elevated lead exposure and BLL can be minimized by strict adherence to the OSHA provisions for functioning decontamination and hygiene facilities and healthy personal hygiene practices.

Forth Road Bridge—maintenance and remedial works

Forth Road Bridge is a suspension bridge with a main span of 1006 metres and side spans of some 408 metres. Approach viaducts to the north and south bring the total length of the structure to just under 2500 metres. The bridge crosses the Firth of Forth some 16 km to the north and west of Edinburgh and was opened in 1964. Traffic has grown significantly from 4 million vehicles using the crossing during its first year of operation to the 24 million vehicles using the bridge last year. This paper lists major projects that have been carried out to strengthen and improve the structure and replace major components and makes reference to continuing major maintenance schemes such as bridge painting and resurfacing. The discovery of significant corrosion in the main cables has resulted in the implementation of a dehumidification scheme to halt or slow down the deterioration and this scheme is described. The preliminary findings of a study to examine the feasibility of replacing or augmenting the main cables and to investigate the long term structural integrity of the anchorages are also detailed.

Intelligent Painting Process Planner for Robotic Bridge Painting

Due to increased government regulations on environment, health, and safety, the cost of on-site bridge painting has quadrupled over the past several years. The construction industry faces a great challenge in how to control the increased costs of bridge painting and meet the regulations at the same time. A possible solution to address this challenge is to develop a robotic bridge painting system. The development of the robotic system can be justified by the potential improvements in safety and productivity. This paper presents the development and testing of an Intelligent Painting Process Planner. The Planner, built based on bridge feature scheme, is the key component for the robotic bridge painting system that integrates the painting process planning, robot path planning, cost optimization, and quality control functions. During the development process, lab experiments were conducted to determine the values of painting process planning parameters and coating thickness distribution functions. Field tests demonstrated that the prototype robotic bridge painting system achieved the specified painting quality using the parameter values provided by the Planner. Areas that need to be improved in the future were also identified.

Effectiveness of neuro-fuzzy recognition approach in evaluating steel bridge paint conditions

The development of digital image recognition techniques has contributed to increased precision in pattern recognition and led to numerous applications in industries. In September 1999, the Indiana Department of Transportation (INDOT) first tried out digital image recognition techniques to steel bridge coating assessment. The purpose of this tryout was to obtain a rust percentage, which was required in the INDOT bridge painting warranty contract, when conducting steel bridge coating investigation. Despite the advantages of digital image recognition, some problems that may cause inaccurate recognition results still exist. Nonuniform illumination (i.e., brightness or darkness or shadow) is one of them. The neuro-fuzzy recognition approach (NFRA) was developed to minimize the effect of nonuniform illumination. In this technical note, the framework of NFRA, its application to steel bridge coating assessment, and its performance comparison to three other image recognition methods will be presented.Key words: neuro-fuzzy recognition approach (NFRA), artificial neural network (ANN), double sampling plan, multiresolution pattern classification (MPC), iterated conditional modes (ICM).

Performance Comparison of Bridge Coating Defect Recognition Methods

Abstract Digital image recognition methods are now being utilized for steel bridge painting surface assessment. Through the use of digital image processing methods, the rust percentage on steel bridge surfaces can be objectively computed. The rust percentage may be crucial for the successful implementation of steel bridge painting warranty contracting since it can be used to decide whether painting contractors should repair painting defects at the end of the warranty period or at any regular inspection. To implement painting warranty contracting, however, appropriately designed recognition methods must be developed first. In this paper, several recognition methods are proposed and evaluated based on their rust recognition performance, and these methods fall into two categories. One uses artificial intelligence methods such as neural networks and fuzzy logic as the backbone for recognition, while the others apply statistical approaches to detect rust areas. Illumination is considered in some of the proposed methods to determine how it affects the recognition results. To test the performance of the proposed methods, a series of comparisons were made based on different environmental conditions.

Budget Allocation for Steel Bridge Paint Maintenance

Government authorities are responsible for managing their available budget so that they gain maximum benefit. Therefore, they must make intelligent decisions as to which projects will be funded and the degree of funding. Dynamic programming (DP), integer programming (IP), and greedy heuristic (GH) approaches have been applied to optimize a two-year budget allocation for repainting steel bridges in Indiana. The optimal solution and the objective function values resulting from application of DP, IP, and GH are similar. The Indiana Department of Transportation (INDOT) divides Indiana into six districts. The results show that District 1 has the highest budget allocation percentage (28%). It has the lowest percent in the first year and the highest percent in the second year. District 2 has the lowest percentage (11%). A sensitivity analysis has been completed to show the potential alternative solutions that assist INDOT decision makers in solving their budget allocation problems.

Artificial intelligence application to bridge painting assessment

Digital image recognition has been experimented for steel bridge painting assessment by the Indiana Department of Transportation (INDOT) in September 1999. Although the application was successfully carried out as a whole, there are still some minor problems left to be improved. Nonuniform illumination is one of the problems that affect the accuracy of recognition results. To address this problem, the neuro-fuzzy recognition approach (NFRA) is proposed, which segments an image into three areas based on illumination and conducts area-based thresholding with the help of an artificial neural network (ANN) and a fuzzy adjustment system. In this paper, the framework of NFRA will be presented, followed by the application of NFRA to steel bridge painting assessment and its performance comparison with the multiresolution pattern classification (MPC) method and the iterated conditional modes (ICM) algorithm. The conclusions will be presented last.