House dust-mite allergen and cat allergen variability within carpeted living room floors in domestic dwellings

Abstract

Exposure to allergens from house dust-mites (Der p 1) and domestic cats (Fel d 1) is associated with symptom severity in atopic subjects with asthma and rhinitis. Assessment of allergen exposure in the domestic environment is normally determined by measurement from a single floor site. We determined the variability of these allergens and protein throughout the whole living room floor area. Dust samples were collected from 1 m2 areas from 16 carpeted living room floors in Wellington, New Zealand, and analyzed for concentrations of Der p 1 and Fel d 1. Mean coefficients of variation for Der p 1 and Fel d 1 were 53.1% (range: 28.5-136.8) and 65.6% (range: 28.5-131), respectively. This study has demonstrated a large variation of house dust-mite and cat allergens within living room floors and thus a single sampling site may not be representative for assessment of an individual's exposure risk. House dust-mite and cat allergen levels from the center of the room, in front of a couch or chair, or from a corner of the room are similar to mean levels from the whole room, these sites may thus be representative of the whole living room floor in large-scale epidemiological studies.

Variation of biocontaminant levels within and between homes — the AIRALLERG study

“…Loan et al collected dust from 16 living room floors that were divided into sections of 1 m 2 and analyzed each section for dust weight and concentrations of Der p 1 and Fel d 1. The authors found that the assumption that a sample from a central area of the living room floor was representative of the whole room was correct for Der p and Fel d 1 (Loan et al, 2003). Simpson et al however found considerably larger variability for the living room and bedroom floors for Der p 1 but this variability was less in the immediate area around soft furnishings and beds than the rest of the room (Simpson et al, 1998).…”

To what extent is allergen exposure a risk factor for the development of allergic disease?

“…One of the assumptions common to most epidemiological studies to date is that the concentration of allergens measured in dust samples collected by vacuuming a single 1 m 2 of settled dust reservoir such as carpet or mattress is a good marker (or ‘index’) of chronic personal exposure. However, it has been clearly demonstrated that there is a huge variation in mite allergen levels between different areas within a single room, suggesting that it is unlikely that a single sampling site is representative for the assessment of individual's exposure . For example, one study has reported a mean coefficient of variation of > 80%, with up to 192‐fold difference in allergen concentrations between dust samples collected from the different square metre areas within the same rooms .…”

Size distributions and height variations of airborne particulate matter and cat allergen indoors immediately following dust-disturbing activities

“…The variability in the levels measured, even within the same room (Loan, Siebers, & Fitzharris, 2003) and during different seasons (Chen, Su, & Lin, 2002), limits the usefulness of such studies in the evaluation of the true exposure risk. This approach, however, remains the most common practice in the field.…”