Cockroach Allergen Reduction Using Precision-Targeted IPM and the Lead Dust Cleaning Protocol

HUD Office of Healthy House and Lead Hazard Control - Cooperative Agreement #OHLHH0069

EPA's Case Study of this Project (pdf, 4 pgs)
National Center for Healthy Homes Case Study (pdf, 4pgs)
Model IPM Contractor Program (pdf, 6 pgs)
Roach Control in Public Housing (pdf, 4 pgs)
Cockroach IPM in Public Housing (pdf, 5 pgs of power point slides)
Cleaning Cockroach Allergen (pdf, 5 pgs of power point slides)
Final Report (pdf, 40 pgs)

Background
There is strong evidence that cockroach allergen is a potent, pervasive and persistent asthma trigger for low-income, inner-city populations. A still-too-common method of cockroach control is monthly pesticide spraying. Children are at high risk for exposure to household pesticides and are particularly vulnerable to their toxic effects. Integrated pest management (IPM) is a reduced risk strategy that utilizes pest population monitoring, environmental controls, mechanical capture and placement of small amounts of low-toxicity, low-volatility pesticides on surfaces inaccessible to children. Due to the persistence of cockroach allergen in the household environment, elimination of cockroach infestation alone may not sufficiently reduce exposure to their allergens. Furthermore, neither householder nor the usual professional cleaning has been reported to consistently reduce dust concentration of cockroach allergen below clinically relevant thresholds.

Interventions
This project explored improved methods of cockroach control and allergen cleanup. The cockroach control intervention was "precision-targeted IPM," a modification of the standard cockroach IPM strategy, designed by the USDA Imported Fire Ants and Household Insects Research Unit (Agricultural Research Station, Gainesville, Florida) a partner in this project. Their approach increases the usual level of cockroach monitoring so that a detailed spatial analysis of harborages and feeding points can be used for more precise placement of pesticide. Roaches were flushed from harborages with a hot air gun and captured with a HEPA vacuum; gel baits and borate powders were placed in harborages identified by the flushing; occupants were educated to reduce food debris and clutter.

The intervention to cleanup cockroach allergen was based on the HUD protocol for cleanup of lead dust on hard surfaces (HEPA vacuuming-mopping and rinsing-HEPA vacuuming). Two modifications to the standard lead cleaning protocol were tested, 1) using a wet vacuum rather than a mop to pick up dirty wash and rinse water and 2) using a wet vacuum and substituting bleach/detergent cleaner for the detergent-only cleaner used in the standard lead cleaning protocol.

The project was carried out in three multi-family complexes operated by the public housing authority in Cleveland, Ohio. A total of 18 housing units were enrolled. Cockroach control interventions were carried out in 14 units and cleaning interventions were carried out in 15 units. Project staff observed live roaches in 11 of 18 units (generally an indication of heavy infestation) and dead roaches in 16 units. All units had been getting regular pest control treatment by a licensed contractor.

Standard lead cleaning and the two modifications were each carried out in 15 units. Vacuum dust samples were taken from 3 rooms in each unit, at pre-cleaning, post-cleaning and follow-up (median=52 days, max=131, min=40). A total of 89 sample points was available for analysis. (Due to a change in laboratories, data from 4 units/12 rooms was not included in the analysis.)

Results
The cockroach control objective was to achieve a 95% reduction in the roach population, as measured by the number of roaches trapped and flushed. This level of reduction was achieved in all but one case and required 1 to 4 flush/vacuum/bait visits.

All three cleaning interventions significantly reduced cockroach allergen concentrations (Bla g 1 and Bla g 2) from pre- to post-cleaning, with no significant difference among the three. All three significantly reduced cockroach allergen concentrations from pre-cleaning to follow-up. Reductions for the standard lead cleaning protocol were significantly greater compared to the two modifications of the protocol (p=0.01).

A concentration of 2 U/g (Bla g 1) has been proposed as a threshold for cockroach allergen sensitization. All three interventions had declines, pre-cleaning to follow-up, in the proportion of values greater than 2 U/g. This was significant only for the standard lead cleaning protocol (p < 0.01).

At follow-up, with the standard lead cleaning, no rooms were above 2 U/g; with the modified cleaning, about a third of the rooms were above 2 U/g. For the standard cleaning, the maximum Bla g 1 concentrations at pre-cleaning, post-cleaning and follow-up were 73.4 U/g, 8.2 U/g, and 1.8 U/g respectively. For the modifications, the comparable concentrations were 223.0 U/g, 24.1 U/g, and 6.8 U/g, respectively. (There was no significant difference in pre-cleaning allergen concentrations among the treatment groups.)

Discussion
The experience of this small exploratory project was that, in all but one case, previously intractable roach infestations were virtually eliminated through a labor-intensive, aggressive and systematic integrated pest management strategy sustained over several months. It required substantial cooperation by the public housing authority management and staff and by the occupants.

The standard lead cleaning protocol and two modifications were generally able to reduce cockroach allergen concentrations to near proposed levels of sensitization. However, for the modifications, the performance was not consistent, with some increased concentrations measured following cleaning.

The better performance of the standard lead cleaning may be due to the increased mechanical abrasion from additional mopping in this treatment as compared to the other two. In the standard lead cleaning treatment, mopping was used to pick up the dirty wash water and rinse water; in the other treatments the wash and rinse water was picked up with a wet vacuum. The two additional mopping passes may be more effective in loosening the dirt so the allergen can be dissolved, suspended and removed.

Cockroach allergen levels generally continued to decline substantially from post-cleaning to follow-up. There were a number of factors that likely contributed to this outcome. There was no longer a continuing input of allergenic material from active roach infestation. The treatment reduced many allergen reservoirs, e.g., rugs, upholstered furniture and bulk debris, which could have contributed to recontamination. On the other hand, some reservoirs were not treated, such as bedding, clothes, and wall voids. The extent of recontamination following treatment probably depends on which of the reservoirs, treated or untreated, dominate. It also appeared that occupant cleaning post-treatment contributed to continued reductions in allergen levels.

A puzzling finding at first glance was low pre-cleaning cockroach allergen levels. Pre-cleaning sampling was done after the initial IPM work had been completed and infestation had been reduced by 95%. The hot air roach flushing and HEPA vacuuming conducted as part of the IPM work removed large numbers of cockroaches and a considerable amount of roach debris. Thus a large amount of allergenic material was removed prior to the first sampling for cockroach allergen.

The failure to sample prior to roach flushing/vacuuming and the small sample size limit the findings on cleaning methods. However, the low allergen concentrations at follow-up suggest that the standard lead cleaning protocol be considered as a point of departure in other studies of cockroach allergen cleaning.

Overall, the combination of cockroach infestation reduction through precision-targeted IPM (including hot air flushing and HEPA vacuuming), a one-time professional cleaning based on the HUD lead dust cleaning protocol, occupant education and occupant on-going cleaning effort was able to substantially reduce cockroach allergen levels.

In the full report (pdf, 40 pgs) , lessons learned from the occupant education efforts are suggested and a Cockroach Control Guide, Model Contractor Program for Cockroach IPM and Recommendations to Public Housing Authorities are provided as appendices. Slide shows presented at a HUD/EPA/CDC Healthy House Conference in June 2004: Cockroach IPM in Public Housing (PowerPoint Presentation) and Cleaning Cockroach Allergen (PowerPoint Presentation).

EPA's Case Study of this Project (pdf, 4 pgs)

(See related article from Environmental Health Perspectives 1997 about USDA-ARS research.)