This study was structured to analyze the seasonal variation of allergens, such as dust mite, cat and cockroach allergens and the total fungi at homes in a city. Over a time period of one year, floor dust was collected from 47 inner-city homes in Minneapolis. Six visits were made to each of the houses and the inhabitants were educated at different intervals. It was observed that about 30 percent of the dust mite and cockroach allergen concentrations were above detection limits. Relative humidity was found to be a good predictor of allergen concentrations, while demographic information, such as race/ethnicity, family income, and the presence of cats was found to influence the seasonal variation of the allergens.
Of late, it appears that there is an increasing incidence of respiratory disorders among populations living within inner-city limits in the United States, especially amongst the low income and minority people. Certain allergens at homes are related to the educational status and socioeconomic status of the residents and the type and year of construction of their homes. Few allergens, such as fungus depend on seasonal variations and geographic locations. A single allergen that could be consistent with an analysis for contamination is highly debated, because of the varying results in different studies that have been conducted. The aim of this study was to assess the seasonal variability of the allergens and examine variations in allergen levels relative to the socioeconomic and housing features. The concentrations of allergens and fungi that were found during the study were also analyzed.
* Forty-seven houses were chosen for the evaluation and three initial visits and dust samplings were done in each of them.
* The houses were categorized into three groups, based on the amount of allergens found and three more visits were made to each of these houses. Intervention on the basis of education and cleaning was done.
* The inhabitants were asked to complete a few questionnaires that assessed their socioeconomic status.
* Dust was collected using a vacuum cleaner. The dust samples were then processed in a laboratory to analyze the quantity of the allergens.
* About 40 percent of the homes had a family income of less than $20,000 annually. Most of the population was predominantly non-English-speaking and a majority of them lived in apartments.
* It was found that 51 percent of the dust samples from houses without cats were positive for cat allergens. Seasonal variation was seen in dust mite allergen and fungal concentrations, but was absent in cat and cockroach allergens.
* Allergen levels were not associated with temperature and were found to have an inverse relation with relative humidity.
* The cat allergens were more common in English-speaking households, while the cockroach allergen concentrations were higher in the non-English-speaking households. The fungal concentrations were similar in both the English-speaking and non-English-speaking homes.
* The variance or probability distribution was found to be highest for the cat allergen at 1.68. The correlation was the least for fungus (0.28), thus making the cat allergen a better factor for exposure assessment.
The levels of dust mites and cockroach allergens were non-detectable in more than 70 percent of the collected samples. This could have been the reason for the conflicts in the seasonal variations in comparison with other studies. A few other alternative methods applied to the data of dust and mite allergen, to achieve positive statistical correlation, were not significant in this study.
Seasonal variability, socioeconomic factors and housing quality were considered in this study. Various common allergens, such as dust mite, cat and cockroach allergens and fungal concentrations were correlated with the above factors. It was seen that few allergens had significant seasonal variations. Certain allergens varied based on the ethnicity/race of the inhabitants and a few allergens varied based on geographic locations and seasons. However, on estimating the variance of each allergen, it was found that more than nine repeated measurements of total culturable fungi were required to estimate long-term allergen exposure. This could, however, be simplified by a single analysis for cat allergen. The cat allergen was found to have correlation values and appeared to be the best feature to estimate the presence of allergens in any household.
For More Information:
Longitudinal Evaluation of Allergen and Culturable Fungal Concentrations in Inner-City Households
Journal of Occupational and Environmental Hygiene, February 2008
By Sook Ja Cho; Gurumurthy Ramachandran; University of Minnesota, Minneapolis
*FYI Living Lab Reports Are Summaries of the Original Research.