Caroline Shorter

Effect of Floorcovering Construction on Content and Vertical Distribution of House Dust Mite Allergen, Der p I

Domestic floorcoverings often contain appreciable quantities of particulate pollutants, such as house dust mite allergen, Der p I. Exposure to Der p I is a risk factor for the development of mite sensitization and asthma. We investigated whether carpet construction was related to the Der p I content in normal use, and its vertical distribution. We hoped to inform development of methods to remove such material. Along with one hard flooring surface, a range of carpets with differing pile conformations (loop vs. cut), pile heights, yarn twists, and pile densities were placed in houses for 13 months. The carpets were later sectioned to allow profiling of Der p I throughout the pile strata using monoclonal antibody, enzyme-linked immunosorbent assay. Not surprisingly, significantly lower amounts of Der p I were found on hard flooring than any of the carpets, which all contained similar amounts of mite allergen. For all carpets, the Der p I concentration per unit area was found to be inversely related to the distance from the carpet backing. We conclude that carpet construction is not a good predictor of Der p I content in the home. We also suggest that, as carpet construction likely influences ease of disturbance of material within the pile, methods to remove or denature particulate pollutants such as Der p I will be most effective if they are able to target the bulk of allergenic material, found toward the base of the pile.

Efficiency of Vacuuming for the Removal of Cat Allergen (Fel d 1) from Worn and Unworn Wool Carpets of Different Construction

Exposure to cat allergen (Fel d 1) has been associated with immune responses and exacerbation of asthma. As such allergen can accumulate in carpet, we sought to determine the influence of carpet pile conformation (loop vs. cut) and degree of wear on the levels of Fel d 1 present before and after different cleaning processes. Tufted wool carpets of different construction were loaded with house dust and artificially worn, before being either dry or wet vacuumed. Using enzyme linked immunosorbent assay to determine Fel d 1 levels at each stage, we showed the efficiency of Fel d 1 extraction from unworn (but soiled) carpets to be high, and to differ little with pile conformation or cleaning method. However, efficiency of removal decreased as the carpet became more worn, in which state wet vacuuming also proved slightly more effective than dry vacuuming. Therefore, if seeking to minimize exposure to cat allergen in a carpeted environment, in addition to established Fel d 1 avoidance techniques, implementation of a regular cleaning regime is desirable and consideration should also be given to removal of any heavily worn carpets (preferencing replacement with constructions of high wear resistance).

Replicating the cross-sectional distribution of house-dust mite allergen found in carpet

With a view to producing carpets that could be used to determine the ease of particulate aerosolisation during domestic activity, we measured the cross-sectional distribution of dust-mite allergen, Der p 1, produced using American Society for Testing and Materials method (ASTM F608–89) for embedding house dust in carpets with that produced by several alternative protocols. Allergen concentrations produced at different levels within the pile using the different techniques were also compared with those in carpets from actual houses – in which the majority of allergen is typically found towards the base of the pile. To obtain profiles of allergen, horizontal sections, 2-mm thick, were taken from new carpets after they had been seeded with dust and embedded using one of four following techniques: (1) dragging a fixed roller across the surface of the carpet four times, (2) using the same roller but following it up with 200 revolutions in a hexapod wear simulator, (3) dragging the fixed roller across the carpet surface 30 times (the ASTM method), and (4) 2 minutes under a commercial plate compactor. Fibre from each 2-mm-thick section was collected and the Der p 1 content determined using enzyme linked immunosorbent assay and results expressed as ng Der p 1 per area in each section. Embedding with a fixed roller alone was not found to be particularly effective, resulting in roughly equal amounts of dust being apportioned within each pile layer, irrespective of the number of embedding passes used. In contrast, a distribution biased towards the base of the pile was found after roller-embedding/hexapod wear, although still to a lesser extent than has been observed in used carpets. Plate compaction gave a similar allergen distribution profile to combined roller/hexapod treatment but was considerably easier to perform. Thus, both techniques offer promise for researchers seeking to replicate the cross-sectional distribution of dust mite allergen found in carpets after actual use (and conceivably other particulate pollutants also).

Endotoxin, cat and house dust mite allergens in electrostatic cloths and bedroom dust

Abstract Environmental exposure to endotoxin, Fel d I (cat) allergen and Der p I (house dust mite) allergen have been associated with asthma symptoms and have been measured in the environment using various sampling methods, including the electrostatic dust collector. The objectives of this study were to investigate whether levels of endotoxin and allergens were detectable in electrostatic dust collectors and to examine the correlation of allergen and endotoxin levels between electrostatic dust collectors and vacuum sampling methods (floor dust and mattress dust). Electrostatic cloths, bedroom floor dust and mattress dust samples from a subset of 60 homes were randomly selected from the Health of Occupants of Mouldy Homes study for allergen and endotoxin analysis. Fel d I and Der p I allergens were analyzed by double monoclonal antibody ELISA and endotoxin by the kinetic Limulus amoebocyte lysate assay. An enhanced ELISA method was used to analyze Der p I in the electrostatic cloths. Endotoxin was detected in all samples, however Fel d I and Der p I were not detected in all electrostatic dust collector samples (detection in 53% and 15% of cloths respectively). No correlations were found between cloth and dust samples for endotoxin or Der p I, but moderate-to-strong correlations were found between all three sampling methods for Fel d I (rs = 0.612–0.715, p < 0.001). Poor correlation was found between floor dust and mattress dust samples for Der p I (rs = 0.256, p = 0.048). Electrostatic dust collectors may provide a way to measure airborne dust and allergen. Given the moderate-to-low correlations with vacuum dust sampling, this may present a unique measurement system which, when collected alongside traditional vacuum dust sampling, could provide additional exposure measures. Further studies are required to correlate endotoxin and allergen levels measured by electrostatic dust collector with air sampling and to explore the relationships between these bioaerosols, environmental factors and asthma.

Effect of repeated freeze/thawing of household dust extracts on β-(1,3)-glucan levels

β-(1,3)-glucan exposure from household dust has been shown to be associated with respiratory symptoms and thus is increasingly being measured in epidemiological studies. Various factors are known to influence its measurement; however, no studies have assessed the effects of sample extract freeze-thawing on β-(1,3)-glucan. The aim of this study was to assess the effects of repeated freeze-thawing of household dust extracts on levels of β-(1,3)-glucan. Forty random household dust samples were extracted with 0.3 M NaOH and aliquots of extracts stored at −20°C were subjected to one, two, and three freeze-thaw cycles. They were analyzed for β-(1,3)-glucan by the Limulus amoebocyte assay (LAL) and results compared to freshly extracted samples (paired Pearsons t-test on logged values). Initial freezing of house dust extracts results in a significant decline in β-(1,3)-glucan. However, repeated freeze/thawing (up to three times) does not results in any further decline in β-(1,3)-glucan levels.

PD47 - Visible mould and dampness are associated with new onset wheezing in New Zealand children

Methods We undertook an incident case control study of 450 children. Cases were children aged 1 – 6 years recently diagnosed with wheezing and requiring treatment in the past 12 months. Each case was area, age and gender matched to two control children with no history of wheezing. The extent of visible mould was scored and mould odour and leaks were examined in the homes of the children by parents and researchers using standard methods.

Penetration of light into carpet, and responses of the European house-dust mite (Dermatophagoides pteronyssinus) to varying light intensity and diurnal cycle.

This study examined the question of what effect exposure to light might play in determining the vertical distribution of house-dust mites in carpet, and the degree to which light penetrates worn and unworn carpets of different pile conformation (loop- versus cut-pile), height and colour. The effect on population increase of a diurnal lighting cycle versus continual darkness was also investigated. It was found that the penetration of light into carpets was largely unaffected by pile colour or conformation. Pile height was an important factor, however, and for a given height within the pile, light intensity was higher in carpets subjected to a greater degree of wear. This corresponded to the reduction in effective pile height that occurs with carpet use. Whilst the differences observed were sometimes large (up to two-fold for a given height within the pile), Petri dish studies suggested no mite preference for habitation of areas of low light intensity compared to high intensity. Additionally, culturing mites under a diurnal light cycle was shown to be no more efficient than culturing in complete darkness. These results suggest that exposure to light is not an important determinant of house-dust mite behaviour, or their ability to colonise textile substrates.