This study focused on determinants of allergen concentrations in public housing with a goal of highlighting key risk factors and groups, thereby focusing intervention efforts and recommendations for operation and policy changes. This is particularly important given the financial constraints faced by many public housing authorities and in other low-income settings.
We found that variations in cockroach allergen concentrations in the air and bed were most highly associated with housekeeping practices, whereas holes in the wall/ceiling were significant in the kitchen but not elsewhere. It appears that having a point of entry is a major determinant of whether cockroaches are able to get into a particular apartment to access available food and water, and housekeeping practice is the major determinant of whether the infestation spreads or the allergen is tracked into and builds up in the bedroom. The significant correlation between kitchen and bed cockroach allergen concentrations (Spearman correlation of 0.55 for Bla g 1, 0.72 for Bla g 2) supports this theory.
Our finding of a significant contribution of deteriorating housing to high cockroach allergen concentrations is consistent with that found by Rauh et al.12
They found a significant association between the degree of disrepair and Bla g 2 concentrations in the kitchen after adjusting for income and ethnicity.
We also found a positive (but insignificant in multivariate models) association between kitchen and bedroom cockroach allergen concentrations and duration of occupancy. However, we found lower allergen concentrations in apartments occupied for less than 2 years rather than higher as reported by Rauh et al.12
In these public housing developments, apartments occupied for less than 2 years may represent apartments in better physical condition. Apartment turnover allows maintenance staff to thoroughly clean, treat, and repair the whole unit. Moreover, short-duration occupancy was greatest in West Broadway, which had major renovations and fewer holes in the wall/ceiling, among other differences, complicating interpretation of this covariate. While this covariate represented “residential stability” for Rauh et al., it may capture a different phenomenon in public housing wherein short-term residents may be more likely to be socioeconomically mobile than long-term residents.
Our study found similar seasonal differences as reported by Mollet et al.27
and Chew et al.17
of higher cockroach allergens in the hotter months. However, the seasonal difference in our population could have been affected in part by increased pest awareness due to a housing authority-wide pest program and benefits to early recruits that may have inspired greater interest in the study in the fall and winter sampling period by those with less severe pest problems. In addition, the summer sampling was done in the Franklin Hill development only, whereas the winter sampling was done in all three developments with the greatest number of winter samples collected in West Broadway.
Our study had comparable median kitchen cockroach allergen concentrations with those reported for the National Cooperative Inner-City Asthma Study (NCICAS),28
three times the levels observed in a Baltimore inner-city study,29
and two orders of magnitude above the geometric mean concentration found in the New York City Columbia Center for Children’s Environmental Health Study (CCCEHS).6
The bed levels for our study were comparable to CCCEHS. The NCICAS bedroom values were a combination of bedroom floor and bed,3
and studies that report both levels often report much higher levels for floor dust than for bed dust.10,30
As a whole, mouse allergen does not appear to be a major problem in these developments in terms of allergen concentrations and number of detects. Self-report of mouse problems was also low. Our mouse levels were much lower than those found in other studies in urban environments.6,7,29,31
Likely due to the lower levels, unlike the NCICAS25
and the National Survey of Lead and Allergen in Housing (NSLAH)31
and similar to the CCCEHS,6
we did not find a significant association between cockroach allergen concentrations and mouse concentrations. We found MUP concentrations to be consistently associated with having pets; however, our analysis did not distinguish among the types of pets, so that the inverse relationship between the presence of cats and mouse allergen concentrations found in the CCCHES6
was not assessed.
There was low detection of dust mite similar to the pattern found by Chew et al.32
and Kitch et al.10
of lower dust mite allergen levels in urban inner-city homes in the Northeast. As in these studies, Der f 1 was more highly detected and had greater percentage above the thresholds. However, in skin-prick tests of our study population, a higher percent of the children showed sensitivity to Der p 1 (59%) than Der f 1 (50%) and an equal percent to cockroach allergen (59%).26
The dust mite sensitivities may have been related to early childhood exposure in another environment.
High airborne concentrations of allergens were frequently associated with a high occupant density, which is not surprising given that greater disturbance of allergen reservoirs occurs with higher levels of human activity. We also found a subset of airborne cockroach allergen concentrations in the bedroom, which was above the existing critical exacerbation level. However, the critical exacerbation thresholds are based on studies that examined bed and floor dust concentrations. Because measurement in air is more relevant to exposure, it could be that a much lower threshold level would be associated with exacerbation than has been found for bed and floor dust.
There are some limitations in interpreting our findings. We evaluated determinants in 49 homes, which limited our power to detect significant predictors. In addition, data were collected in three housing developments, two of which had not been renovated and one of which had. However, the plausible causal pathways and magnitude of the associations even after controlling for renovation status strengthen our interpretations. In addition, some of the predictive variables had only small numbers in the groups, which could result in unstable estimates, and multiple predictors were correlated with one another. More generally, public housing is unique in its design, structure, and operation, which may not make the results generalizable to other housing types. However, the associations are consistent in terms of what is known about the influence of building conditions and about pest ecology.
Even though unrenovated developments have higher cockroach allergen concentrations, there are very high concentrations in all three public housing developments we evaluated, which need to be addressed. Residents reported that pest infestation particularly by cockroaches is one of their key issues of concern. Providing physical and educational interventions has been proposed as a means of reducing allergen concentrations. Concerted efforts by the public housing management to keep the basements sealed and clean in these developments have probably already contributed to lower concentrations of mouse allergen. To successfully control the cockroach population, building and unit conditions will need to be addressed, such as holes in the walls and ceiling. Interventions also need to focus on education about the role of housekeeping and strategies for making homes less hospitable to pests.
Our study highlights that even among households with similar housing structures and administration, there is variability in the allergen concentrations and number of allergens at high concentrations. This implies that while some pest remediation activities must be focused on the building, other efforts must address characteristics of the unit and resident.