Effects of HUD-supported lead hazard control interventions in housing on children's blood lead.

The Evaluation of the US Department of Housing and Urban Development Lead-Based Paint Hazard Control Grant Program studied the effectiveness of the housing intervention performed in reducing the blood lead of children at four post-intervention times (6-months, 1-year, 2-years, and 3-years). A repeat measures analysis showed that blood lead levels declined up to three-years post-intervention. The results at each successive collection time were significantly lower than at the previous post-intervention time except for the difference between the levels at two and three years. At two-years post-intervention, geometric mean blood lead levels were approximately 37% lower than at pre-intervention. Children with pre-intervention blood lead levels as low as 10 µg/dL experienced substantial declines in blood lead levels. Previous studies have found substantial improvements only if a child's pre-intervention blood lead level was above 20 µg/dL. Individual interior lead hazard control treatments as grouped by Interior Strategy were not a significant predictor of post-intervention blood lead levels. However, children living in dwellings where exterior lead hazard control interventions were done had lower blood lead levels at one-year post-intervention than those living in dwellings without the exterior interventions (all other factors being equal), but those differences were only significant when the mean exterior paint lead loading at pre-intervention was about the 90th percentile (7.0mg/cm(2)). This observation suggests that exterior lead hazard control can be an important component of a lead hazard control plan. Children who were six to eleven months of age at pre-intervention had a significant increase in blood lead at one-year post-intervention, probably due to other exposures.

Improving cost-effectiveness of epidemiological studies via designed missingness strategies.

Modern epidemiological studies face opportunities and challenges posed by an ever-expanding capacity to measure a wide range of environmental exposures, along with sophisticated biomarkers of exposure and response at the individual level. The challenge of deciding what to measure is further complicated for longitudinal studies, where logistical and cost constraints preclude the collection of all possible measurements on all participants at every follow-up time. This is true for the National Children's Study (NCS), a large-scale longitudinal study that will enroll women both prior to conception and during pregnancy and collect information on their environment, their pregnancies, and their children's development through early adulthood-with a goal of assessing key exposure/outcome relationships among a cohort of approximately 100 000 children. The success of the NCS will significantly depend on the accurate, yet cost-effective, characterization of environmental exposures thought to be related to the health outcomes of interest. The purpose of this paper is to explore the use of cost saving, yet valid and adequately powered statistical approaches for gathering exposure information within epidemiological cohort studies. The proposed approach involves the collection of detailed exposure assessment information on a specially selected subset of the study population, and collection of less-costly, and presumably less-detailed and less-burdensome, surrogate measures across the entire cohort. We show that large-scale efficiency in costs and burden may be achieved without making substantive sacrifices on the ability to draw reliable inferences concerning the relationship between exposure and health outcome. Several detailed scenarios are provided that document how the targeted sub-sampling design strategy can benefit large cohort studies like the NCS, as well as other more focused environmental epidemiologic studies.

Selecting a lead hazard control strategy based on dust lead loading and housing condition: I. Methods and results.

A methodology was developed to classify housing conditions and interior dust lead loadings, using them to predict the relative effectiveness of different lead-based paint hazard control interventions. A companion article in this issue describes how the methodology can be applied. Data from the National Evaluation of the HUD Lead Hazard Control Grant Program, which covered more than 2800 homes in 11 U.S. states, were used. Half these homes (1417) met the study's inclusion criteria. Interior interventions ranged from professional cleaning with spot painting to lead abatement on windows, and enclosure, encapsulation, or removal of other leaded building components. Modeling was used to develop a visual Housing Assessment Tool (HAT), which was then used to predict relative intervention effectiveness for a range of intervention intensities and baseline floor and windowsill dust lead loadings in occupied dwellings. More than 117,000 potential HATs were considered. To be deemed successful, potential HATs were required to meet these criteria: (1) the effect of interior strategy had to differ for HAT ratings of good vs. poor building condition and/or baseline dust lead loadings; (2) the HAT rating had to be a predictor of one year post-intervention loadings; (3) interior intervention strategy had to be a predictor of one-year loadings; (4) higher baseline loadings could not be associated with lower one-year loadings; and (5) neither exterior work nor site/soil work could result in higher predicted one-year loadings for either HAT rating. Of the 1299 HATs that met these criteria, one was selected because it had the most significant differences between strategy intensities when floors and sills were considered together. For the selected HAT, site/soil work was a predictor of one-year loadings for floors (p = 0.009) but not for sills (p = 0.424). Hazard control work on the building exterior was a predictor of both sill and floor one-year loadings (p = 0.004 and p < 0.001, respectively). Regardless of the type of interior intervention strategy, interior work was a predictor of both floor and sill one-year loadings (each p < or = 0.001).

Selecting a lead hazard control strategy based on dust lead loading and housing condition: II. Application of Housing Assessment Tool (HAT) modeling results.

In Part I in this issue, modeling was used to identify a Housing Assessment Tool (HAT) that can be used to predict relative intervention effectiveness for a range of intervention intensities and baseline dust lead loadings in occupied dwellings. The HAT predicts one year post-intervention floor and windowsill loadings and the probability that these loadings will exceed current federal lead hazard standards. This article illustrates the field application of the HAT, helping practitioners determine the minimum intervention intensity needed to reach "acceptable" one year post-intervention levels, with acceptability defined based on specific project needs, local needs, regulations, and resource constraints. The HAT is used to classify a dwelling's baseline condition as good or poor. If the average number of interior non-intact painted surfaces per room is >/=2, then the dwelling is rated as poor. If exterior windows/doors are deteriorated and the average number of exterior non-intact painted surfaces per building side is >/=5, then the dwelling is rated as poor. If neither of these conditions is true, then the dwelling's HAT rating is good. The HAT rating is then combined with baseline average floor loading to help select the treatment intensity. For example, if the baseline floor loading is 100 mug/ft(2) (1,075 mug/m(2) and the HAT rating is poor, the probability that the one-year floor loading exceeds the federal standard of 40 mug/ft(2) (430 mug/m(2) is 27% for a high-intensity strategy (i.e., window lead abatement with other treatments) but is 54% for a lower-intensity strategy (i.e., cleaning and spot painting). If the HAT rating is good, the probability that the one-year floor loading exceeds 40 mug/ft(2) is approximately the same for low- and high-intensity strategies (18% for window lead abatement with other treatments compared with 16% for cleaning and spot painting). Lead hazard control practitioners can use this information to make empirically based judgments about the treatment intensity needed to ensure that one year post-intervention loadings remain below federal standards.

The relationship between housing and health: children at risk.

In November 2002, the National Center for Healthy Housing convened a 2-day workshop to review the state of knowledge in the field of healthy housing. The workshop, supported with funds from the U.S. Centers for Disease Control and Prevention's National Center for Injury Prevention and Control and National Center for Environmental Health, was unique in that it focused solely on the effect of housing on children's health and the translation of research findings into practical activities in home construction, rehabilitation, and maintenance. Participants included experts and practitioners representing the health, housing, and environmental arenas. Presentations by subject-matter experts covered four key areas: asthma, neurotoxicants, injury, and translational research. Panel discussions followed the presentations, which generated robust dialogue on potential future research opportunities and overall policy gaps. Lack of consensus on standard measurements, incomplete understanding about the interaction of home hazards, inadequate research on the effectiveness of interventions, and insufficient political support limit current efforts to achieve healthy housing. However, change is forthcoming and achievable. Key words: asthma, childhood exposure, environmental toxicants, healthy housing, lead poisoning.

Friction and impact surfaces: are they lead-based paint hazards?

Professionals who identify residential lead-based paint hazards and develop lead hazard control plans are instructed to assess painted friction and impact surfaces in homes as potentially active sources of dust lead, a known exposure vector for young children. However, empirical tests of the importance of these surfaces had not been conducted. Using data collected as part of a 1998 three-community study of the Housing and Urban Development Lead Risk Assessment protocols, this article explores how much rubbing or binding on friction and impact surfaces on windows and doors influence dust lead levels on windowsills and floors, while taking into account paint condition on these surfaces and other sources of lead. The analyses included windowsill dust wipe samples from 611 rooms in 182 homes and 782 floor dust wipe samples collected in 209 rooms from 104 homes. The study found that when the paint on windows is intact but the window is rubbing or binding, the dust lead levels on the windowsills are significantly higher than on windows with intact paint without rubbing or binding, after controlling for other lead sources. Windowsill dust lead on a window with intact lead-based paint at 1 mg/cm(2) and no rubbing/binding would be 27% lower than on a window with nonintact paint, rubbing/binding surfaces, or both of these conditions. An independent effect of rubbing/binding of doors on floor dust lead loadings was not observed. These findings support federal regulations calling for lead risk assessors to check the friction/impact surfaces at windows when dust lead samples taken below them are elevated, but these analyses did not offer support for taking extra observations of friction/impact surfaces around doors.

An investigation of dust lead sampling locations and children's blood lead levels.

The objective of this study is to provide guidance on where to collect dust lead wipe samples in homes to best characterize the risk of a resident child having a blood lead level at or above the CDC level of concern (10 microg/dl). In 1998, the Milwaukee Health Department enrolled 72 children living in pre-1950 buildings: 34 had elevated (i.e., > or = 10 microg/dl) blood lead levels (EBL); and 38 had non-elevated blood lead levels (non-EBL). This study explored dust lead sampling locations by examining loading differences between homes where children with EBL and non-EBL lived. Floor, windowsill, and window trough samples were collected in the living room, kitchen, bathroom, and child's bedroom and play area. Floor samples were collected at four locations: room entry; center of the room; under a window; and against the wall opposite the window (perimeter). Geometric mean floor dust lead levels were generally two to three times higher in homes of EBL children than homes of non-EBL children. Sampling the floor at the room entry or center is preferable to sampling under the window or from the perimeter of the room. When the central floor average was used, the room combinations that had the greatest differences between homes of EBL children and non-EBL children all included a sample from the child's bedroom and excluded the bathroom. When the entry floor average was used, the greatest differences also excluded bathrooms, but otherwise included a mix of all of the other rooms. Window samples did not distinguish where children with EBLs versus non-EBLs resided. This paper is based on Milwaukee alone, so generalizing results to other locations should be done with caution.

Immediate and one-year post-intervention effectiveness of Maryland's lead law treatments.

A 1994 Maryland law prescribes a lead-based paint risk reduction standard for pre-1950, privately owned rental housing. This standard, applied at each tenancy change, can be met by sampling to verify that dust lead loadings are within acceptable limits or by performing specific lead hazard reduction treatments, followed by an independent visual inspection without dust sampling. We evaluated the ability of visual inspection to predict treatment completion and dust lead loadings. Fifty-two Baltimore housing units were enrolled and received the law-specified treatments. Before treatment, study risk assessors conducted visual assessments and dust lead wipe sampling in each unit. After treatment, Maryland-certified visual inspectors conducted the law's required visual inspection, followed by the study risk assessors, who performed a separate visual assessment and collected dust wipe samples. One year later, study risk assessors performed another visual assessment and dust wipe sampling (n=34). Dust lead loadings declined significantly immediately after prescribed lead treatments were implemented. Fifty-three percent, 20%, and 47% of units had at least one sample that exceeded 1995 EPA/HUD floor, window sill and window trough clearance guidance of 100, 500 and 800 microg/ft2, respectively. Overall, 73% of units had one or more immediate post-intervention single surface sample results exceeding the 1995 clearance values that were in effect at the time of the study. One-year post-intervention loadings remained significantly below pre-intervention levels for floors but not window sills or troughs. Visual assessments alone, without dust lead testing, did not ensure that prescribed treatments were completed or that dust lead loadings were below clearance values.

The influence of common area lead hazards and lead hazard control on dust lead loadings in multiunit buildings.

Owners of multiunit buildings built before 1978 that have interior common areas, and who receive certain forms of federal assistance are generally required to address lead-based paint hazards in those common areas. This study examines the relationships between common area paint and dust lead levels and the floor dust lead loadings in associated dwelling units, as well as the effects of lead hazard control treatments in common areas. This article presents data from common areas in 145 low-income, mostly pre-1940, multiunit buildings with 342 associated dwellings in the U.S. Department of Housing and Urban Development Lead Hazard Control Grant Program at preintervention, clearance, and 1-year postintervention. Interior common areas in these multiunit buildings were not as well maintained as the dwellings in the buildings. At preintervention, a higher percent of the interior common areas had non-intact, lead-based paint on windows, doors and trim, and other interior components than in associated dwellings (95% versus 85%; 78% versus 67%; and 85% versus 62%). Common areas had preintervention entry and interior (i.e., nonentry) floor dust lead loadings more than four times higher than in dwelling units (128 versus 30 micro g/ft(2); 130 versus 28 micro g/ft(2)) while 1-year postintervention common area dust lead loadings are four to six times that of dwelling dust lead loadings (41 versus 11 micro g/ft(2); 44 versus 8 micro g/ft(2)). Windowsill dust lead loadings in common areas were twice the loadings in dwelling units at preintervention and 1-year postintervention (756 versus 383 mu g/ft(2); 154 versus 68 micro g/ft(2)). Interior common area treatments reduced geometric mean common entry dust lead loadings 71% from preintervention to clearance, and maintained those reduced levels from clearance to 1-year postintervention. Higher level interventions were not more effective than low-level interventions in reducing preintervention levels to clearance or 1-year postintervention. This study demonstrates that interior common areas in the multiunit buildings examined contain substantial amounts of deteriorated lead-based paint and dust. Remediation of common areas can effectively reduce those hazards.

Effectiveness of lead-hazard control interventions on dust lead loadings: findings from the evaluation of the HUD Lead-Based Paint Hazard Control Grant Program.

From 1994 to 1999, the Evaluation of the US Department of Housing and Urban Development Lead-Based Paint Hazard Control Grant Program studied the intervention experiences of over 2800 homes in 11 states in the USA. Each interior intervention was categorized as (in order of increasing intensity) (a) cleaning/spot painting; (b) complete repainting; (c) complete repainting plus window treatments; (d) window abatement plus treatments to other components; (e) abatement of all lead-based paint hazards; or (f) abatement of all lead-based paint. Complete dust testing and environmental data were available for 1034 and 278 dwellings through 12 and 36 months postintervention, respectively. Strategies ranging from complete repainting to window abatement plus other treatments reduced geometric mean preintervention windowsill and floor dust lead loadings up to 36 months postintervention (reductions for complete repainting, from 16 to 5 microg/ft2 on floors and 182 to 88 microg/ft2 on sills; for window abatement plus other treatments, 27-8 microg/ft2 on floors and 570-124 microg/ft2 on sills). Full abatement reduced windowsill and floor loadings from baseline to 12 months postintervention [95-6 microg/ft2 on floors and 518-30 microg/ft2 on sills (data were not available for this strategy at 36 months)]. Window lead-hazard abatement was the most effective measure to reduce dust lead loadings on windows, but this treatment would need to be performed in conjunction with treatments to floors as well as exterior and soil treatments for the most effective control of dust lead on floors.

National evaluation of the US Department of Housing and Urban Development Lead-Based Paint Hazard Control Grant Program: study methods.

The US Department of Housing and Urban Development (HUD) undertook an evaluation of its Lead Hazard Control Grant Program between 1994 and 1999. The Evaluation is the largest study ever done on the effectiveness of lead hazard controls implemented in residential dwellings. The Evaluation had several major objectives: determining the effectiveness of various lead hazard controls in reducing residential dust lead levels and children's blood lead levels, establishing the costs of doing lead hazard control work and factors that influence those costs, determining the rate of clearance testing failures and their causes, and identifying possible negative effects of lead hazard control work on children's blood lead levels. This paper reports the overall research design and data collection methods of the Evaluation. The large number of dwelling units enrolled in the Evaluation was possible only by the innovative partnership among HUD, the Evaluators, and the grantees. HUD and the Evaluators relied on the grantees for essentially all of the data collection. The 14 participating HUD Lead Hazard Control Grantees were responsible for implementing the lead hazard control programs in their communities and collecting the study data. This paper describes the methods for recruiting and enrolling dwellings and families, collecting environmental and housing data, interviewing participating families, and collecting data on lead hazard control work performed and its costs. The paper also describes the basic quality control and quality assurance procedures used. The principal outcome measures were lead in dust collected using wipes from floors, window sills, and window troughs and lead in blood collected from children who were 6 years old or younger at enrollment. Data collection was conducted before intervention, immediately postintervention, and 6 and 12 months postintervention. For a subset of dwellings undergoing an extended follow-up data were also collected at 24 and 36 months postintervention. This paper provides the context for subsequent reports that will describe such findings as the influence of lead hazard control work on serial dust lead levels, the influence of lead hazard control work on serial blood lead levels in children, the nature and costs of the lead hazard control work done at the dwellings, and the experience of the grantees in meeting clearance testing requirements.

Imputation of data values that are less than a detection limit.

Results of the analyses of occupational and environmental samples are frequently reported as "less than a specified value," a practice followed by many analytical laboratories. A left-censored distribution occurs when analytical laboratories do not report results that fall below their limits of detection or quantification. Approximately 37% of the household interior dust lead loadings collected in a large-scale, multisite, longitudinal study of lead-based paint hazard controls were reported to be below the "method detection limit." These unreported values are unusable in any statistical analysis of the data and must be replaced by a valid dust lead loading estimate, a process called data imputation. This investigation tested how well data imputed using a newly formulated procedure for estimating the data below the method detection limit were correlated with dust lead loadings reported by the participating laboratories after special request. These results were also compared with those obtained by imputing the minimum detectable level by the square root of 2. Imputation of the low lead loadings was accomplished by substituting the value associated with the median percentile below each laboratory's method detection limit. A correlation of r = 0.50 was calculated between the predicted and reported dust lead loadings, with only slight bias (2.9%) in the predicted values. An alternative imputation procedure that used the predicted value from structural equation models fit to the noncensored dust lead loadings performed about as well, although the predictions had to be "centered" to correspond to the censored data. An estimator that combined both of these imputation procedures only slightly improved the correlation between the predicted and laboratory values (r = 0.51). These results support the use of the new procedure rather than the commonly used imputed values of the method detection limit divided by 2 or by the square root of 2. Imputing values based on either of these common approaches may result in much more biased predictions for the censored data; in the case of these data, the dust lead loadings were overestimated by 348%. The results also suggest that analytical laboratories should provide a numerical result for all analyzed samples, with a "flag" of those values below their detection limit, since these results may be more accurate than any imputed value, particularly those provided by the commonly used method of dividing the minimum detection limit by the square root of 2.

Occurrence and determinants of increases in blood lead levels in children shortly after lead hazard control activities.

This study is an examination of the effect of lead hazard control strategies on children's blood lead levels immediately after an intervention was conducted as part of the US Department of Housing and Urban Development's Lead-Based Paint Hazard Control Grant Program. Fourteen state and local government grantees participated in the evaluation. The findings indicated an overall average reduction in the blood lead levels of 869 children soon after the implementation of lead hazard controls. However, 9.3% of these children (n = 81) had blood lead increases of 5 microg/dL or more. Data routinely collected as part of the evaluation, as well as additional information supplied by the individual programs, were used to determine potential reasons for these observed increases in blood lead. A logistic regression analysis indicated that three principal factors were associated with the blood lead increases: the number of exterior deteriorations present in the child's home (prior to intervention), the educational level of the female parent or guardian of the child, and the child's age. The statistical analysis did not find evidence that children living in households that either did not relocate or relocated for less than the full work period were significantly more likely to have a blood lead increase equal to or greater than 5 microg/dL than children living in households that fully relocated. Statistical analyses also did not reveal any single interior strategy to be more or less likely than others to be associated with a blood lead increase of 5 microg/dL or more.

The influence of exterior dust and soil lead on interior dust lead levels in housing that had undergone lead-based paint hazard control.

To aid in understanding the contribution of exterior dust/soil lead to postintervention interior dust lead, a subset of housing from the HUD Lead-Based Paint Hazard Control Grant Program Evaluation was selected for study. Housing from 12 state and local governments was included. Exterior entry and street dust samples were obtained by a vacuum method, and soil samples were building perimeter core composites. Interior dust wipe lead data (microg/ft(2)) and paint lead data (mg/cm(2)) were also available for each of the dwelling units and included in the modeling. Results from 541 dwelling units revealed a wide range of exterior dust and soil lead levels, within and between grantees. Minimum and maximum geometric mean lead levels, by grantee, were 126 and 14400 microg/ft(2) for exterior entry dust; 325 and 4610 microg/ft(2) for street dust; and, for soil concentration, 383 and 2640 ppm. Geometric mean exterior entry dust lead concentration (1641 ppm) was almost four times as high as street dust lead concentration (431 ppm), suggesting that lead dust near housing was often a source of street dust lead. Geometric mean exterior entry dust lead loading was more than four times as high as window trough dust lead loading and more than an order of magnitude higher than interior entry dust lead loading. Statistical modeling revealed pathways from exterior entry dust lead loading to loadings on interior entryway floors, other interior floors, and windowsills. Paint lead was found to influence exterior entry dust lead. Results of this study show that housing where soil lead hazard control activities had been performed had lower postintervention exterior entry, interior entry floor, windowsills, and other floor dust loading levels. Soil was not present for almost half the buildings. Statistical analysis revealed that exterior strategy influenced soil lead concentration, and soil lead concentration influenced street dust lead loading. This study represents one of the few where an impact of soil treatments on dust lead levels within the housing has been documented and may represent the first where an impact on exterior entry dust lead has been found. The inclusion of measures to mitigate the role of exterior sources in lead hazard control programs needs consideration.

Prevalence and location of teeth marks observed on painted surfaces in an evaluation of the HUD lead hazard control grant program.

Data from an evaluation of the HUD Lead Hazard Control Grant Program were used to evaluate the prevalence and location of teeth marks on painted surfaces in residential housing. The results of these analyses will be useful in the development of more effective pediatric lead poisoning prevention programs. These programs have historically placed considerable emphasis on surfaces accessible to children for mouthing activities. This study analyzes the largest set of data ever assembled on the prevalence of teeth marks in housing. Data from 308,851 observations in 3,454 housing units were analyzed to determine the prevalence of teeth mark observations per surface, dwelling unit, and building component, and by housing age, inspector, and grantee. An average of 4.0 teeth marks per 10,000 surfaces with paint-lead greater than or equal to 1.0 mg/cm2 were observed. For surfaces with less than 1.0 mg/cm2 lead the rate was 1.5 teeth marks/10,000 surfaces. The number of teeth marks per 10,000 surfaces increased with age of housing for surfaces with 1.0 mg/cm2 or higher lead but not for surfaces with less than 1.0 mg/cm2 lead. Teeth mark observation rates were 36 times higher for windowsills than for other components and ranged up to 11 per 10,000 surfaces and 9 dwellings per 100 dwelling units for 2 grantees with the highest rates. Blood lead levels in children exhibiting moderate to high mouthing behavior were higher than in children without such behavior, especially in housing where teeth marks were observed. Special priority should be given to windowsills when making decisions on lead hazard control for "accessible," "chewable," or "mouthable" surfaces.

An evaluation of one-time professional cleaning in homes with lead-based paint hazards.

A key challenge in reducing the burden of lead poisoning is to identify cost-effective interventions that minimize lead-based paint hazards. One-time professional cleaning of lead-contaminated dust and debris was conducted in 37 housing units with deteriorated lead-based paint and dust lead hazards. These study units are a subset of a larger cohort of the nearly 3500 housing units enrolled in the Evaluation of the HUD Lead-Based Paint Hazard Control Grant Program. Dust lead loading measurements were taken prior to cleaning, immediately after cleaning (i.e., clearance), and six months, one, two, and three years post-intervention. The cleaning intervention significantly reduced dust lead loadings on floors, windowsills, and window troughs immediately following the work. However, these reductions did not persist at six months and one year post-intervention. Six months and one year post-intervention dust lead loadings are not significantly different from the pre-intervention loadings on either bare floors or windowsills. Although window trough lead loadings declined over 50 percent from pre-intervention to one year post-intervention, the loadings rebounded markedly from the geometric mean at clearance of 101 microgram/ft(2) to 5500 microgram/ft(2) at 6 months and 5790 microgram/ft(2) at one-year post-intervention. These results demonstrate that a single professional cleaning of dust and debris without addressing potential sources of lead dust (such as deteriorated lead-based paint) or repeating the cleaning are unlikely to result in significant and sustained reductions in dust lead loadings. More extensive interventions that address deteriorated lead-based paint, although more expensive, are likely to provide longer term reductions in dust lead loadings. Cleaning strategies, however, may be useful in emergency situations to reduce lead dust hazards when paint repair and other lead hazard control activities cannot be done immediately.

Residential dust lead loading immediately after intervention in the HUD lead hazard control grant program.

At the conclusion of most lead hazard control interventions in federally assisted housing built before 1978, a certified clearance examiner must verify that the lead hazard control work was completed as specified and that the area is safe for residents, a process referred to as clearance. This study explores the experience of 14 grantees participating in the Evaluation of the HUD Lead-Based Paint Hazard Control Grant Program in passing clearance. The study also considers how preintervention lead levels (interior dust and paint), building condition/characteristics, and the scope of work influenced initial clearance dust lead loadings and clearance rates. At the initial clearance inspection, 80% of the 2682 dwellings achieved grantee-specific clearance standards on windowsills, window troughs (500 microg/ft2 and 800 microg/ft2, respectively), and floors (80, 100, or 200 microg/ft2 depending on state/local regulations at the dates of clearance in the mid-1990s), with individual grantee success rates ranging from 63 to 100%. Dwellings that failed initial clearance required an average of 1.13 retests to clear. The high level of success at clearance demonstrates that following methods for work site containment, lead hazard control, and cleaning similar to those recommended in the HUD Guidelines for the Evaluation and Control of Lead-Based Paint in Housing is effective. The most common lead hazard control intervention was window abatement accompanied by the repair or abatement of all other deteriorated lead-based paint (56% of dwellings). An additional 5% of dwellings were fully abated, 29% had lower intensity interventions. Interventions including window replacement are recommended to reduce dust lead loading on windowsills and troughs at clearance, but lower level interventions such as full paint stabilization are just as good at reducing floor dust lead loadings. Whatever lead hazard control activities are selected, the condition of the surfaces of interest should be in good condition at clearance.