The Environmental Relative Moldiness Index reveals changes in mold contamination in United States homes over time.

The Environmental Relative Moldiness Index (ERMI) is a scale created to compare mold contamination levels in U.S. homes. The ERMI was developed as a result of the Department of Housing and Urban Development's (HUD) first American Healthy Homes Survey (AHHS I), which sampled 1,096 homes selected to be representative of the U.S. housing stock. In AHHS I, a dust sample from each home was analyzed using quantitative PCR assays (qPCR) for 36 common indoor molds: 26 Group 1 molds, which were associated with water damage in homes and 10 Group 2 molds, which primarily enter the home from the outside environment. In 2019, HUD completed AHHS II by sampling 695 homes. Because lead was banned from paint in 1978, a larger proportion of homes selected for AHHS II had been built before 1978 compared to AHHS I. The 36 ERMI molds were analyzed in AHHS II exactly as in AHHS I. For the 36-ERMI molds, the rates of detection, average concentrations, and geometric means were in significant concordance (p < 0.001) between AHHS I and II, indicating that the ERMI methodology was stable over time. However, the average ERMI value in AHHS II homes was greater than in AHHS I. The reason for the difference was investigated by examining the Group 1 and 2 mold populations. The average summed logs of Group 1 molds were significantly greater in homes built before 1978 than the average for homes built later. Conversely, the average summed logs of Group 2 mold populations were the same in homes built before 1978 and homes built later. Since the summed logs of Group 2 mold is subtracted from the summed logs of Group 1 molds in the ERMI calculation, the average ERMI value was higher in AHHS II homes than AHHS I. In conclusion, by using the ERMI metric, we were able to demonstrate that water damage and mold growth were more likely to occur as homes get older.

Comparison of ERMI results for dust collected from homes by an electrostatic cloth and by the standard vacuum method.

The Environmental Relative Moldiness Index (ERMI) is a scale used to compare mold contamination levels in U.S. homes. To create the ERMI scale, a nationally representative set of U.S. homes was selected (n = 1,096). From each of these homes, a standard vacuum-dust sample was collected and then 36 common molds, the 26 Group 1 and 10 Group 2 molds, as grouped for forming the ERMI metric, were quantified using quantitative PCR assays. However, in investigations of mold in homes, it is not always practical or even possible to collect dust using the standard vacuum method. Therefore, we performed a comparative study of dust samples collected in the same homes (n = 151) by the standard vacuum method and by an electrostatic cloth (EC) method. First, floor dust was collected by vacuuming a 2 m2 area in the living room and a 2 m2 area in a bedroom, directly adjacent to the sofa or bed, for 5 min each with a Mitest sampler-fitted vacuum. Second, immediately after the collection of the vacuum dust sample, an EC dust sample was collected by wiping above-floor horizontal surfaces in the living room and bedroom. Then, the ERMI analysis of each sample was performed by a commercial laboratory. The results showed the average concentrations of 33 of the 36 ERMI molds were not significantly different in the vacuum and EC samples. Also, the average summed logs of the Group 1 molds, Group 2, or ERMI values were significantly (p < 0.001) correlated between the vacuum and EC samples. Logistic regression indicated that an EC sample could identify homes in the highest ERMI quartile 96% of the time by using the same ERMI value cutoff as vacuum sample ERMI value cutoff and 35% of samples proved to be false positives. When it is not practical to obtain the standard vacuum-dust sample, an EC sample can provide a useful practical alternative for ERMI analyses.

Prevalence of Lead Hazards and Soil Arsenic in U.S. Housing.

The American Healthy Homes Survey, June 2005-March 2006, measured levels of lead and arsenic in homes nationwide. Based on a three-stage cluster sample of 1,131 housing units, key statistically weighted estimates of the prevalence of lead-based paint (LBP) and LBP hazards associated with paint, dust, and soil, and arsenic in dust and soil, were as follows: 37.1 million homes (35%) had some LBP; 23.2 million (22%) had one or more LBP hazards; 93% of the homes with LBP were built before 1978. The highest prevalence of LBP and LBP hazards was in the Northeast and Midwest. Over three million homes with children under six years of age had LBP hazards, including 1.1 million low-income households (< $30,000/yr.). Less than 5% of homes had detectable levels of arsenic in dust (≥ 5 µg/ft2). Arsenic in soil (for homes with yard soil) averaged 6.6 parts per million (ppm). Many homes had soil arsenic levels of 20 ppm or greater, including 16% of homes with wooden structures in the yard and 8% of homes without such structures.

United States house dust Pb concentrations are influenced by soil, paint, and house age: insights from a national survey.

BACKGROUND: Lead (Pb) in house dust contributes significantly to blood lead levels (BLLs) in children which may result in dire health consequences. Assessment of house dust Pb in the United States, relationships with Pb in soil and paint, and residential factors influencing Pb concentrations are essential to probing drivers of house dust Pb exposure. OBJECTIVE: Pb concentrations in vacuum-collected house dust are characterized across 346 homes participating in the American Health Homes Survey II (AHHS II), a US survey (2018-2019) evaluating residential Pb hazards. Connections between house dust Pb and soil Pb, paint Pb, and other residential factors are evaluated, and dust Pb concentration data are compared to paired loading data to understand Pb hazard standard implications. RESULTS: Mean and median vacuum dust Pb concentrations were 124 µg Pb g-1 and 34 µg Pb g-1, respectively. Vacuum-collected dust concentrations and dust wipe Pb loading rates were significantly correlated within homes (α < 0.001; r ≥ 0.4). At least one wipe sample exceeded current house dust Pb loading hazard standards (10 µg ft-2 or 100 µg Pb ft-2 for floors and windowsills, respectively) in 75 of 346 homes (22%). House dust Pb concentrations were correlated with soil Pb (r = 0.64) and Pb paint (r = 0.57). Soil Pb and paint Pb were also correlated (r = 0.6). IMPACT: The AHHS II provides a window into the current state of Pb in and around residences. We evaluated the relationship between house dust Pb concentrations and two common residential Pb sources: soil and Pb-based paint. Here, we identify relationships between Pb concentrations from vacuum-collected dust and paired Pb wipe loading data, enabling dust Pb concentrations to be evaluated in the context of hazard standards. This relationship, along with direct ties to Pb in soil and interior/exterior paint, provides a comprehensive assessment of dust Pb for US homes, crucial for formulating effective strategies to mitigate Pb exposure risks in households.

Lead, allergen, and pesticide levels in licensed child care centers in the United States.

The First National Environmental Health Survey of Child Care Centers was conducted to provide information about lead, allergen, and pesticide levels in licensed U.S. child care centers. Lead levels were measured in settled dust, paint, and play area soil; indoor allergen levels were measured in settled dust; and pesticide residues were measured on indoor surfaces and in play area soil. Fourteen percent of centers had significant lead hazards, suggesting that an estimated 470,000 children under age six (approximately 10% of all children in licensed centers) attend centers with significant lead hazards. Approximately 5% of centers had levels of allergens associated with asthma and allergic conditions. Three-quarters of centers had pesticides applied (either indoors or outdoors) during the previous year. Although most centers did not appear to present risks from lead and allergens, some centers did have unsafe levels of these contaminants. These conclusions cannot be generalized to unlicensed child care arrangements.

Reduced prevalence of childhood asthma after housing renovations in an underresourced community.

Background: Despite improvements in asthma symptom management and asthma morbidity, the prevalence of asthma in the United States remains high, especially in underresourced communities. Objective: Our goal was to determine whether housing renovations affect the prevalence of asthma in an underresourced community. Methods: The Fay Apartments (~800 units) in Cincinnati, Ohio, were renovated to "green building" standards between 2010 and 2012 and renamed the Villages at Roll Hill. The prevalence of asthma among 7-year-olds in the Villages at Roll Hill was determined by accessing Ohio Medicaid data for the years 2013 to 2021. Results: In the first 6 years after the renovations (2013-2018), the prevalence of asthma among 7-year-olds in the community averaged 12.7%. In contrast, in postrenovation years 7 through 9 (2019-2021), the average prevalence of asthma was 5.9%. Logistic regression modeling for the log odds of asthma diagnosis in this age group was used to test the statistical significance of asthma prevalence for 2013-2018 versus for 2019-2021. The model resulted in demonstration of a significant (P < .001) reduction in asthma prevalence between 2013-2018 and 2019-2021. Conclusions: The renovation of an underresourced community's housing resulted in a lower prevalence of asthma for 7-year-olds who were born after the renovations had been completed.

A national survey of lead and other metal(loids) in residential drinking water in the United States.

BACKGROUND: Exposure to lead (Pb), arsenic (As) and copper (Cu) may cause significant health issues including harmful neurological effects, cancer or organ damage. Determination of human exposure-relevant concentrations of these metal(loids) in drinking water, therefore, is critical. OBJECTIVE: We sought to characterize exposure-relevant Pb, As, and Cu concentrations in drinking water collected from homes participating in the American Healthy Homes Survey II, a national survey that monitors the prevalence of Pb and related hazards in United States homes. METHODS: Drinking water samples were collected from a national survey of 678 U.S. homes where children may live using an exposure-based composite sampling protocol. Relationships between metal(loid) concentration, water source and house age were evaluated. RESULTS: 18 of 678 (2.6%) of samples analyzed exceeded 5 µg Pb L-1 (Mean = 1.0 µg L-1). 1.5% of samples exceeded 10 µg As L-1 (Mean = 1.7 µg L-1) and 1,300 µg Cu L-1 (Mean = 125 µg L-1). Private well samples were more likely to exceed metal(loid) concentration thresholds than public water samples. Pb concentrations were correlated with Cu and Zn, indicative of brass as a common Pb source is samples analyzed. SIGNIFICANCE: Results represent the largest national-scale effort to date to inform exposure risks to Pb, As, and Cu in drinking water in U.S. homes using an exposure-based composite sampling approach. IMPACT STATEMENT: To date, there are no national-level estimates of Pb, As and Cu in US drinking water collected from household taps using an exposure-based sampling protocol. Therefore, assessing public health impacts from metal(loids) in drinking water remains challenging. Results presented in this study represent the largest effort to date to test for exposure-relevant concentrations of Pb, As and Cu in US household drinking water, providing a critical step toward improved understanding of metal(loid) exposure risk.

The prevalence of lead-based paint hazards in U.S. housing.

In this study we estimated the number of housing units in the United States with lead-based paint and lead-based paint hazards. We included measurements of lead in intact and deteriorated paint, interior dust, and bare soil. A nationally representative, random sample of 831 housing units was evaluated in a survey between 1998 and 2000; the units and their occupants did not differ significantly from nationwide characteristics. Results indicate that 38 million housing units had lead-based paint, down from the 1990 estimate of 64 million. Twenty-four million had significant lead-based paint hazards. Of those with hazards, 1.2 million units housed low-income families (< 30,000 US dollars/year) with children under 6 years of age. Although 17% of government-supported, low-income housing had hazards, 35% of all low-income housing had hazards. For households with incomes greater than or equal to 30,000 US dollars/year, 19% had hazards. Fourteen percent of all houses had significantly deteriorated lead-based paint, and 16% and 7%, respectively, had dust lead and soil lead levels above current standards of the U.S. Department of Housing and Urban Development and the U.S. Environmental Protection Agency. The prevalence of lead-based paint and hazards increases with age of housing, but most painted surfaces, even in older housing, do not have lead-based paint. Between 2% and 25% of painted building components were coated with lead-based paint. Housing in the Northeast and Midwest had about twice the prevalence of hazards compared with housing in the South and West. The greatest risk occurs in older units with lead-based paint hazards that either will be or are currently occupied by families with children under 6 years of age and are low-income and/or are undergoing renovation or maintenance that disturbs lead-based paint. This study also confirms projections made in 2000 by the President's Task Force on Environmental Health Risks and Safety Risks to Children of the number of houses with lead-based paint hazards. Public- and private-sector resources should be directed to units posing the greatest risk if future lead poisoning is to be prevented.

First National Survey of Lead and Allergens in Housing: survey design and methods for the allergen and endotoxin components.

From July 1998 to August 1999, the U.S. Department of Housing and Urban Development and the National Institute of Environmental Health Sciences conducted the first National Survey of Lead and Allergens in Housing. The purpose of the survey was to assess children's potential household exposure to lead, allergens, and bacterial endotoxins. We surveyed a sample of 831 homes, representing 96 million permanently occupied, noninstitutional housing units that permit resident children. We administered questionnaires to household members, made home observations, and took environmental samples. This article provides general background information on the survey, an overview of the survey design, and a description of the data collection and laboratory methods pertaining to the allergen and endotoxin components. We collected dust samples from a bed, the bedroom floor, a sofa or chair, the living room floor, the kitchen floor, and a basement floor and analyzed them for cockroach allergen Bla g 1, the dust mite allergens Der f 1 and Der p 1, the cat allergen Fel d 1, the dog allergen Can f 1, the rodent allergens Rat n 1 and mouse urinary protein, allergens of the fungus Alternaria alternata, and endotoxin. This article provides the essential context for subsequent reports that will describe the prevalence of allergens and endotoxin in U.S. households, their distribution by various housing characteristics, and their associations with allergic diseases such as asthma and rhinitis.

Geographic distribution of Environmental Relative Moldiness Index molds in USA homes.

OBJECTIVE: The objective of this study was to quantify and describe the distribution of the 36 molds that make up the Environmental Relative Moldiness Index (ERMI). MATERIALS AND METHODS: As part of the 2006 American Healthy Homes Survey, settled dust samples were analyzed by mold-specific quantitative PCR (MSQPCR) for the 36 ERMI molds. Each species' geographical distribution pattern was examined individually, followed by partitioning analysis in order to identify spatially meaningful patterns. For mapping, the 36 mold populations were divided into disjoint clusters on the basis of their standardized concentrations, and First Principal Component (FPC) scores were computed. RESULTS AND CONCLUSIONS: The partitioning analyses failed to uncover a valid partitioning that yielded compact, well-separated partitions with systematic spatial distributions, either on global or local criteria. Disjoint variable clustering resulted in seven mold clusters. The 36 molds and ERMI values themselves were found to be heterogeneously distributed across the United States of America (USA).

American Healthy Homes Survey: a national study of residential pesticides measured from floor wipes.

The U.S. Department of Housing and Urban Development in collaboration with the United States Environmental Protection Agency conducted a survey measuring lead, allergens, and insecticides in a randomly selected nationally representative sample of residential homes. Multistage sampling with clustering was used to select the 1131 homes of which a subset of 500 randomly selected homes included the collection of hard surface floor wipes. Samples were collected by trained field technicians between June 2005 and March 2006 using isopropanol wetted wipes. Samples were analyzed for a suite of 24 compounds which included insecticides in the organochlorine, organophosphate, pyrethroid and phenylpyrazole classes, and the insecticide synergist piperonyl butoxide. The most commonly detected were permethrin (89%), chlorpyrifos (78%), chlordane (64%), piperonyl butoxide (52%), cypermethrin (46%), and fipronil (40%). Mean and geometric mean (GM) concentrations varied widely among compounds, but were highest for trans-permethrin (mean 2.22 ng/cm2 and GM 0.14 ng/ cm2) and cypermethrin (mean 2.9 ng/cm2 and GM 0.03 ng/ cm2). Results show that most floors in occupied homes in the U.S. have measurable levels of insecticides that may serve as sources of exposure to occupants.

Development of an Environmental Relative Moldiness index for US homes.

OBJECTIVE: The objective of this study was to establish a national relative moldiness index for homes in the United States. METHODS: As part of the Housing and Urban Development's American Healthy Homes Survey, dust samples were collected by vacuuming 2 m in the bedrooms plus 2 m in the living rooms from a nationally representative 1096 homes in the United States using the Mitest sampler. Five milligrams of sieved (300 mum pore, nylon mesh) dust was analyzed by mold-specific quantitative polymerase chain reaction for the 36 indicator species in 1096 samples. RESULTS: On the basis of this standardized national sampling and analysis, an "Environmental Relative Moldiness Index" was created with values ranging from about -10 to 20 or above (lowest to highest). CONCLUSIONS: The Environmental Relative Moldiness Index scale may be useful for home mold-burden estimates in epidemiological studies.

Pesticide measurements from the first national environmental health survey of child care centers using a multi-residue GC/MS analysis method.

The U.S. Department of Housing and Urban Development, in collaboration with the U.S. Consumer Product Safety Commission and the U.S. Environmental Protection Agency, characterized the environments of young children (<6 years) by measuring lead, allergens, and pesticides in a randomly selected nationally representative sample of licensed institutional child care centers. Multi-stage sampling with clustering was used to select 168 child care centers in 30 primary sampling units in the United States. Centers were recruited into the study by telephone interviewers. Samples for pesticides, lead, and allergens were collected at multiple locations in each center by field technicians. Field sampling was conducted from July through October 2001. Wipe samples from indoor surfaces (floors, tabletops, desks) and soil samples were collected at the centers and analyzed using a multi-residue GC/MS analysis method. Based on the questionnaire responses, pyrethroids were the most commonly used pesticides among centers applying pesticides. Among the 63% of centers reporting pesticide applications, the number of pesticides used in each center ranged from 1 to 10 and the frequency of use ranged from 1 to 107 times annually. Numerous organophosphate and pyrethroid pesticides were detected in the indoor floor wipe samples. Chlorpyrifos (0.004-28 ng/cm2), diazinon (0.002-18 ng/cm2), cis-permethrin (0.004-3 ng/cm2), and

Evaluation of HUD-funded lead hazard control treatments at 6 years post-intervention.

The Evaluation of the HUD Lead-Based Paint Hazard Control Grant Program (Evaluation) was a HUD-funded study of the effectiveness of lead hazard control (LHC) treatments conducted by 14 grantees in communities across the country. A stratified random sampling scheme was used to select treated units at four grantee sites for continued environmental assessment at 6 years post-intervention. The study compared the relative effectiveness after 6 years of the different classes of interventions used by the grantees, after controlling for such factors as housing conditions and characteristics and resident and neighborhood characteristics. Geometric mean dust-lead levels on floors and window sills were 11% and 23% lower, respectively, at 6 years post-intervention than at any preceding point following the intervention. Although geometric mean window trough dust-lead levels were slightly higher at 6 years post-intervention than at other post-intervention time periods, they were still over 75% lower than before intervention. Treatment at more-intensive levels was associated with lower window sill and window trough dust-lead levels; however, statistical modeling found no significant difference in floor dust-lead loadings over time between the levels of treatment; however, significant differences in window sill and window trough dust-lead levels between treatment levels were evident. Findings from the 6-Year Extension study indicate that across all grantees and treatment strategies the treatments applied were effective at significantly reducing environmental lead levels on floors, window sills, and window troughs at least 6 years following the intervention.

Efficiency of final cleaning for lead-based paint abatement in indoor environments.

The effectiveness of procedures used for the final indoor cleaning after active lead-based paint abatement were evaluated in a 830 ft3 test chamber. Dry and wet scraping and dry machine sanding were applied to wooden doors obtained from lead-hazard control sites. The airborne particle concentration and size distribution were monitored using a real-time particle size spectrometer. Particulates were also collected on filters and analyzed for total dust and lead. The resulting airborne lead mass was determined for each cleaning procedure, and the potential floor lead loading resulting from the dust settling was calculated. Wipe samples were collected to measure the actual floor lead loading. The effectiveness of final cleaning was evaluated first for dry abatement methods. Various cleaning work practices were tested by applying wet and dry debris sweeping as well as no sweeping in combinations with wet and dry removal of plastic sheeting. Considerable resuspension of leaded particles was detected during dry sweeping: the airborne lead mass increase ranged between 65 and 220 percent. However, this increase did not exceed 22 percent when wet sweeping was applied. Minimal or no resuspension was found when the plastic was folded with leaded debris inside (no sweeping was performed prior to the sheeting removal). During folding activity, the "clean" (uncovered) floor surface may be significantly contaminated with leaded dust from workers' shoes and cleaning tools. The first HEPA vacuuming resulted in a 15- to 20-fold decrease of the airborne lead mass; however, it was not sufficient to reduce the floor lead loading to the U.S. Department of Housing and Urban Development (HUD) clearance level of 40 microg/ft2, as determined by wipe sampling. Wet mopping following the first HEPA vacuuming was proven to be effective to reduce the lead loading significantly below 40 microg/ft2. The second HEPA vacuuming resulted in further reduction of the airborne lead mass concentration. The floor lead loading remained much lower than 40 microg/ft2. These results were confirmed in the tests when using wet scraping. Overall, the HUD-recommended cleaning protocol was found to be sufficient in reducing the floor lead loading below 40 microg/ft2. At the same time, several modifications are proposed in this study to further improve the cleaning effectiveness.

Dynamic monitoring of the dust pickup efficiency of vacuum cleaners.

This study evaluated a new method that uses an optical aerosol photometer for dynamically monitoring dust pickup efficiency during vacuuming. In the first stage of this study the new method was compared with built-in dirt sensors installed by vacuum cleaner manufacturers. Through parallel testing it has been shown that the widely available built-in dirt sensors are not sensitive enough to register small (< 53 microm) dust particles. Therefore, only the optical photometer was used in the rest of the experiments of this study to monitor the dust pickup efficiency while the vacuum cleaner was operated with different nozzles on clean and soiled carpet and vinyl sheet flooring. This method also was used to monitor dust pickup efficiency when vacuuming carpets originating from lead-contaminated homes. The dust pickup efficiencies obtained with the optical aerosol photometer have been compared with the surface lead concentrations found during different stages of cleaning. Results indicate that the dust mass concentration registered with the optical aerosol photometer at the nozzle outlet correlates well with the dust mass collected in the vacuum cleaner filter bag and with the surface lead level. Therefore, dynamic dust pickup monitoring can provide valuable information about the efficiency of cleaning when a vacuum cleaner is used. This suggests that a small aerosol photometer similar to a light-scattering smoke detector would be beneficial in vacuum cleaners used for cleaning surfaces contaminated with leaded dust and biological particles (including allergens).

Dog allergen (Can f 1) and cat allergen (Fel d 1) in US homes: results from the National Survey of Lead and Allergens in Housing.

BACKGROUND: Exposures to dog and cat allergens are believed to play important roles in the etiology of asthma; however, the levels of these allergens have never been assessed in a representative sample of US homes. OBJECTIVE: The objective of this study was to estimate and characterize exposures to Can f 1 (dog allergen) and Fel d 1 (cat allergen) in US homes. METHODS: Data were obtained from the National Survey of Lead and Allergens in Housing, a nationally representative survey of 831 US homes. Vacuumed-collected dust samples from the bed, bedroom floor, living room floor, and living room sofa were analyzed for concentrations of Can f 1 and Fel d 1 (micrograms of allergen per gram of dust). RESULTS: Although a dog or cat had lived in only 49.1% of homes in the previous 6 months, Can f 1 and Fel d 1 were detected in 100% and 99.9% of homes, respectively. Averaged over the sampled sites, geometric mean concentrations (microg/g) were 4.69 for Can f 1 and 4.73 for Fel d 1. Among homes with an indoor dog and cat, respectively, geometric mean concentrations were 69 for Can f 1 and 200 for Fel d 1. Among homes without the indoor pet, geometric mean concentrations were above 1.0. The independent predictors of elevated concentrations in homes without pets were all demographic variables that were also linked to a higher prevalence of pet ownership. CONCLUSIONS: Can f 1 and Fel d 1 are universally present in US homes. Levels that have been associated with an increased risk of allergic sensitization were found even in homes without pets. Because of the transportability of these allergens on clothing, elevated levels in homes without pets, particularly among demographic groups in which pet ownership is more prevalent, implicate the community as an important source of these pet allergens.

House dust mite allergen in US beds: results from the First National Survey of Lead and Allergens in Housing.

BACKGROUND: Although exposure to house dust mite allergen is a major risk factor for allergic sensitization and asthma, nationwide estimates of dust mite allergen levels in US homes have not been reported. OBJECTIVE: The purpose of this study was to estimate the prevalence of dust mite allergen in beds of US homes and to identify predictors of dust mite allergen concentration. METHODS: Data were obtained from the first National Survey of Lead and Allergens in Housing, a cross-sectional survey of 831 permanently occupied noninstitutional housing units that permitted resident children. Dust mite allergen concentration (Der f 1 plus Der p 1) was determined from a dust sample collected from a bed. The percentages of homes with concentrations at or greater than detection, 2.0 microg/g bed dust, and 10.0 microg/g bed dust were estimated. Independent predictors of allergen concentration were assessed with multivariable linear regression. RESULTS: The percentages of US homes with dust mite allergen concentrations at or greater than detection, 2.0 microg/g, and 10.0 microg/g were 84.2% (SE, 1.73), 46.2% (SE, 2.0), and 24.2% (SE, 2.1), respectively. Independent predictors of higher levels were older homes, non-West census regions, single-family homes, no resident children, lower household income, heating sources other than forced air, musty or mildew odor, and higher bedroom humidity. CONCLUSION: Most US homes have detectable levels of dust mite allergen in a bed. Levels previously associated with allergic sensitization and asthma are common in US bedrooms. Predictors can be used to identify conditions under which homes are more likely to have increased dust mite allergen levels.