Indoor dust is a measurable reservoir for pet, mite, cockroach and mold allergens, but the available evidence is regional rather than a single national average. The statistics below distinguish settled-dust concentrations from airborne exposure and identify each study’s population, period and limitations.
Key Indoor Dust Statistics
The most useful headline findings are:
- In home visits published in 2006, dog antigen was measurable in 92% of 777 Cincinnati homes.
- In the same Cincinnati cohort, cat antigen was measurable in 87% of 777 homes during the study home visits.
- Alternaria antigen occurred in 87% of 777 Cincinnati floor-dust samples from the ongoing birth cohort, published in 2006.
- House-dust-mite allergen was measurable in 38% of 777 Cincinnati homes in the 2006 home visits.
- Cockroach allergen was measurable in 14% of 777 Cincinnati homes in the same 2006 study.
- At least one allergen was found in 86.0% of 999 northeastern homes of asthmatic children at the study’s lower cut point in birth-cohort home interviews published in 2006.
- At least two allergens were found in 49% of those 999 northeastern homes at the lower cut point in the 2006 study.
- The geometric-mean Alternaria concentration was 47.3 micrograms per gram of dust in 774 Cincinnati floor-dust samples analyzed for the 2006 publication.
- The geometric-mean dog-antigen concentration was 23.3 micrograms per gram of dust in 775 Cincinnati floor-dust samples.
- In one-month postpartum home visits published in 2014, detectable mite allergen occurred in 36.0% of urban and 39.2% of suburban Detroit homes.
- Detectable cockroach allergen occurred in 12.2% of urban and 4.2% of suburban Detroit homes in the 2014 Detroit bedroom-floor samples.
- Detectable cat allergen occurred in 73.6% of urban and 81.3% of suburban Detroit homes during the same postpartum visits.
- Daily-or-more vacuuming had an adjusted house-dust-mite concentration ratio of 0.83 versus vacuuming at most once weekly in a Cincinnati observational model published in 2006.
- Homes with relative humidity of at least 45% had higher mite-allergen levels than homes below 45% in a Swedish three-climate study published in 1995.
- Indoor humidity was below 35% in 82% of rural Northern Rocky Mountain residences sampled in the study published in 2015.
- In Puerto Rico regional dust sampling published in 2016, the average ERMI mold index was 14.5 in regions with childhood asthma prevalence above 30%, versus 9.3 in regions below 30%.
- Dust-mite, dog or cat antigens were detected in 90% of 14 Puerto Rico bed-dust samples in the 2016 study.
- Exposure above 0.60 micrograms per gram of Der p 1 was associated with an asthma-severity odds ratio of 1.52 among sensitized children with asthma in a 2013 cohort study.
Contents
- Key Indoor Dust Statistics
- How Commonly Household Allergens Are Detected
- Indoor Dust Allergen Concentrations in Floors and Bedrooms
- Dust-Mite Statistics by Humidity, Temperature and Housing
- Pets, Cockroaches and Neighborhood Type
- Indoor Dust, Mold and Microbial Measurements
- Indoor Dust Exposure and Asthma-Related Outcomes
How Commonly Household Allergens Are Detected
Detection means that an assay found measurable antigen in the sampled settled dust. It does not mean that a home had a visible infestation, that a pet lived there, or that the measured material was airborne.
In 777 Cincinnati homes, the 2006 study found measurable Alternaria antigen in 87% of primary activity-room floor-dust samples. The same sample found cat antigen in 87%, dog antigen in 92%, house-dust-mite Der f 1 in 38% and cockroach Bla g 1 in 14% of homes.
These were regional cohort homes, not a representative national estimate. (The effect of home characteristics on dust antigen concentrations and loads in homes)
Among 999 homes of asthmatic children in Connecticut and south-central Massachusetts, the 2006 birth-cohort study found at least one allergen in 86.0% of homes at its lower cut point and 58.0% at its upper cut point. Forty-nine percent had at least two allergens at the lower cut point; the cut points differed by allergen and were exposure categories rather than universal health thresholds. (Dust mite, cockroach, cat, and dog allergen concentrations in homes of asthmatic children in the northeastern United States)
Indoor Dust Allergen Concentrations in Floors and Bedrooms
The Cincinnati results show why prevalence and concentration answer different questions. A home can have a detectable allergen, while the geometric mean describes the distribution of measured amounts among analyzed samples.
| Cincinnati floor-dust measure | Geometric mean | Samples and unit |
|---|---|---|
| Alternaria concentration | 47.3 | 774; micrograms per gram of dust |
| Alternaria loading | 14.8 | 774; micrograms per square meter |
| Cat Fel d 1 concentration | 2.0 | 775; micrograms per gram of dust |
| Cat Fel d 1 loading | 0.6 | 775; micrograms per square meter |
| Dog antigen concentration | 23.3 | 775; micrograms per gram of dust |
| Dog antigen loading | 7.3 | 775; micrograms per square meter |
| Dust-mite Der f 1 concentration | 0.5 | 774; micrograms per gram of dust |
| Dust-mite Der f 1 loading | 0.2 | 774; micrograms per square meter |
The Cincinnati source reported that 10% of Alternaria, 13% of cat, 8% of dog and 62% of Der f 1 samples were below their lower detection limits. Loading is settled dust per sampled floor area, not an airborne concentration. (The effect of home characteristics on dust antigen concentrations and loads in homes)
Detroit provides a bedroom-floor comparison from one-month postpartum home visits published in 2014. Detectable mite allergen occurred in 36.0% of 523 urban homes and 39.2% of 470 suburban homes; among detectable samples, geometric means were 0.11 and 0.12 micrograms per gram, respectively. (Comparison of Indoor Allergen Levels in Urban and Suburban Detroit)
Dust-Mite Statistics by Humidity, Temperature and Housing
Humidity, ventilation, room use and cleaning behavior appeared alongside mite measurements, but most of these findings are observational associations. They should not be read as intervention trials.
- In the Cincinnati model, daily-or-more vacuuming was associated with a house-dust-mite concentration ratio of 0.83 compared with vacuuming at most once weekly.
- Cincinnati bedroom samples had a 1.24 adjusted Der f 1 concentration ratio compared with busy-room samples.
- Dehumidifier use was associated with a 1.14 adjusted Der f 1 loading ratio in Cincinnati homes; the association may reflect homes that already had humidity problems.
- A Swedish three-climate study published in 1995 detected dust-mite allergen in 62% of homes with children.
- The Swedish study reported Der p I concentrations from below 16 nanograms to 50 micrograms per gram of dust and Der f I concentrations from below 16 nanograms to 73 micrograms per gram.
- Swedish homes at relative humidity of at least 45% had higher mite-allergen levels than homes below 45%.
- Swedish homes with ventilation below 0.5 air changes per hour had higher mite-allergen levels, although few homes exceeded that ventilation level.
The rural Northern Rocky Mountain residence study, published in 2015 for western Montana and northern Idaho, measured a notably dry sample: 82% of homes were below 35% indoor humidity, 11% were at 35% to 45%, and 4% were above 45%. Two homes lacked temperature or humidity measurements, so the categories do not sum to 100%.
The maximum recorded indoor temperature was 28.5 degrees Celsius and maximum relative humidity was 50.1%; these are maximum readings, not averages. (Dust Allergens within Rural Northern Rocky Mountain Residences)
Pets, Cockroaches and Neighborhood Type in Indoor Dust Data
Detroit measurements show differences by urban or suburban setting, but they also show why allergen detection cannot be substituted for household ownership.
| Detroit bedroom-floor measure | Urban | Suburban | Period and population |
|---|---|---|---|
| Detectable cockroach allergen | 12.2% | 4.2% | One-month postpartum visits, 2014 |
| Detectable dog allergen | 55.1% | 65.0% | Same visits |
| Detectable cat allergen | 73.6% | 81.3% | Same visits |
| Carpet present | 71.9% | 81.9% | Same homes |
| Dog living in home | 18.8% | 26.4% | Survey characteristic |
| Cat living in home | 7.2% | 21.0% | Survey characteristic |
Among detectable samples, geometric-mean dog allergen was 0.13 micrograms per gram in urban homes and 0.28 in suburban homes. Cat allergen was 0.18 and 0.63 micrograms per gram, respectively; the means were restricted to detectable samples. (Comparison of Indoor Allergen Levels in Urban and Suburban Detroit)
Even without an indoor dog, detectable dog allergen occurred in 45.5% of urban and 54.3% of suburban Detroit homes. The result suggests transported or residual allergen, but the cross-sectional design cannot identify its source; likewise, detectable cat or dog allergen is not equivalent to current ownership.
Indoor Dust, Mold and Microbial Measurements
Puerto Rico regional sampling linked dust measurements with regional childhood-asthma prevalence, but the result was ecological rather than an individual risk estimate. Across eight health regions, the average ERMI mold index was 14.5 where lifetime childhood asthma prevalence exceeded 30%, compared with 9.3 where prevalence was below 30%; only 26 floor-dust samples were included.
The same 2016 Puerto Rico study detected Der p 1, Der f 1 or Blo t 5 antigens in 90% of 14 bed-dust samples. Antigen presence does not measure dose or health effect. (Mold populations and dust mite allergen concentrations in house dust samples from across Puerto Rico)
The Rocky Mountain study also illustrates analytical limits. Only 13 canine-allergen samples were within the assay standard curve for accurate concentration measurement, and those samples averaged 5,357.8 nanograms per gram of dust with a standard deviation of 13,714.6 nanograms per gram.
Group-2 mite allergens were identified in three Rocky Mountain residences, where the average concentration was 1,602.5 nanograms per gram with a standard deviation of 1,737.2. Without the full denominator, the three positive residences are not a population prevalence estimate. (Dust Allergens within Rural Northern Rocky Mountain Residences)
A 2017 review of early-life US home exposures reported that at least six detectable allergens occurred in more than half of samples from 831 homes, while a 2020 US farming-population dust microbiome study recorded carpet in the vacuumed room for 93% of 879 participants. Both figures describe their cited cohorts, not national housing prevalence. (Update on Indoor Allergens and Their Impact on Pediatric Asthma)
Indoor Dust Exposure and Asthma-Related Outcomes
Asthma studies use study-defined cut points, and those thresholds are not universal clinical standards. In the northeastern asthmatic-child homes, the lower and upper dust-mite cut points were 2.0 and 10 micrograms per gram of dust; cockroach cut points were 1.0 and 4.0 units per gram; cat cut points were 1.0 and 8.0 micrograms per gram; and dog cut points were 2.0 and 10.0 micrograms per gram. (Dust mite, cockroach, cat, and dog allergen concentrations in homes of asthmatic children in the northeastern United States)
A childhood asthma-morbidity cohort published in 2013 found that 15% of homes exceeded 2 micrograms per gram for Der p 1 and 35% exceeded that level for Der f 1. Twenty percent exceeded 7.8 micrograms per gram for Fel d 1, and among those high-Fel d 1 homes, 51% did not report a cat.
The same study found Can f 1 above 1.2 micrograms per gram in 30% of homes; 36% of those high-Can f 1 homes did not report dog ownership. Bla g 1 exceeded the 0.60-unit-per-gram detection threshold in 26% of homes in a small-city and suburban asthma study. (Update on Indoor Allergens and Their Impact on Pediatric Asthma)
For children who were both sensitized and exposed to Der p 1, exposure above 0.60 micrograms per gram was associated with an asthma-severity odds ratio of 1.52, with a 95% confidence interval of 1.10 to 2.10. This is an observational association among children with asthma, not proof that settled dust caused the severity outcome.