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A Custovic

Publications and source records attributed to A Custovic.

88 records · Page 5Linked to original sources
PubMed1998

Distribution, aerodynamic characteristics, and removal of the major cat allergen Fel d 1 in British homes.

BACKGROUND: Sensitisation to cat allergen (Fel d 1) is an important risk factor for asthma in the UK. A study was undertaken to investigate the distribution of cat allergen in British homes, the aerodynamic characteristics and particle size distribution of airborne Fel d 1, and the method of removing it. METHODS: Dust was collected from 50 homes with a cat and from 50 homes without a cat, and airborne levels of Fel d 1 were measured in 50 homes with a cat and 75 homes without a cat. Particle size distribution was determined using an Andersen sampler (8 hours/day) in 10 homes with cats. This was repeated on five separate days in a house with four cats, and then one, two, four, seven, and 14 days after the cats were removed from the living room area. The effect of high efficiency particulate air (HEPA) cleaner on airborne levels of Fel d 1 was investigated in seven homes with cats. Samples were collected on two separate days from two rooms of each house concurrently, one of which contained the cat, one day with the HEPA cleaner on and the other day as a control. Three one hourly samples were collected over a nine hour period (baseline, 4-5 hours, 8-9 hours) using a high volume dust sampler (air flow rate 60 l/min) and the air sample was collected onto a microglass fibre filter (pore size 0.3 micron). RESULTS: Fel d 1 concentrations were much lower in houses without a cat than in those with a cat (260-fold difference (95% CI 167 to 590) in living room carpets: geometric mean (GM) 0.9 microgram/g (range 0.06-33.93) versus 237 micrograms/g (range 2.8-3000); 314-fold difference (95% CI 167 to 590) in upholstered furniture: 1.21 micrograms/g (range 0.06-61.9) versus 380 micrograms/g (range 7.1-6000); 228-fold difference (95% CI 109 to 478) in bedroom carpets: 0.24 microgram/g (range 0.06-2.24) versus 55 micrograms/g (range 0.06-2304); and 215-fold difference (95% CI 101 to 456) in mattresses: 0.2 microgram/g (range 0.06-2.3) versus 55 micrograms/g (range 0.06-3400). Airborne levels of Fel d 1 were detected in all houses with cats, and the levels varied greatly between the homes (range 0.7-38 ng/m3). Low concentrations of airborne Fel d 1 (range 0.24-1.78 ng/m3) were found in 22 of 75 homes without a cat. Although airborne Fel d 1 was mostly associated with large particles (> 9 microns, approximately 49% of the allergen recovered), small particles (< 4.7 microns) comprised approximately 23% of the total airborne allergen. Total airborne Fel d 1 was reduced by 61.7% two days after removal of the cat but this was due predominantly to the decrease in larger particles (> 4.8 microns) which fell to 13% of their baseline level. Fel d 1 levels associated with small particles (< 4.8 microns) remained largely unchanged on days 1, 2 and 4 and then slowly decreased to 33% of the baseline levels at day 14. With HEPA cleaner a significant reduction in airborne Fel d 1 was observed compared with the control sampling (GM 5.04-0.88 ng/m3 versus 3.79-1.56 ng/m3 at baseline and 8 hours, active versus control group; p = 0.008). CONCLUSIONS: Airborne Fel d 1 was detectable in undisturbed conditions in all homes with cats and in almost a third of homes without cats. In houses with cats a significant proportion (23%) of airborne Fel d 1 was associated with small particles (< 4.7 microns diameter). Removal of the cat from the living room and bedroom areas of the home and the use of HEPA air cleaner reduced airborne levels of cat allergen in homes with cats, but the reduction following cat removal was not evenly spread across the particle size range.

Air Pollution, Indoor↗
PubMed1998

Role of the indoor environment in determining the severity of asthma.

Allergen exposure can confound the management of asthma. To understand the potential mechanisms by which allergens increase the steroid requirements in atopic asthmatics, we examined the effects of allergens on glucocorticoid receptor (GCR) binding affinity and glucocorticoid (GC) responsiveness of peripheral blood mononuclear cells (PBMC) from atopic asthmatics. A significant reduction (p < 0.001) in the GCR binding affinity (Kd) was observed in ragweed-allergic asthmatics during ragweed pollen season compared with PBMC obtained before and after ragweed season. In vitro effects of allergen on PBMC GCR Kd were also examined by incubating PBMC from atopic asthmatics with allergen (ragweed and cat) versus Candida albicans. GCR binding affinity was significantly reduced after incubation with ragweed (p < 0.001) or cat allergen (p < 0.001) compared with baseline or C. albicans stimulation. This effect was limited to atopic asthmatics in that in vitro cat allergen incubation for 48 h failed to significantly alter GCR binding affinity in nonasthmatic, atopic individuals. These allergen-induced reductions in GCR binding affinity also rendered the PBMC less sensitive to the inhibitory effects of hydrocortisone and dexamethasone on allergen-induced proliferation (p < 0.01). To test the hypothesis that allergen-induced alterations in GCR binding affinity were cytokine-induced, we examined the effects of interleukin-2 (IL-2) and IL-4 neutralization using anticytokine antibodies. Addition of both anti-IL-2 and anti-IL-4 antibodies resulted in a significant (p < 0.001) inhibition of allergen-induced alterations in GCR binding affinity. Furthermore incubation with cat allergen induced significantly higher concentrations of IL-2 (p = 0.03) and IL-4 (p = 0.02) by PBMC from atopic as compared with nonatopic subjects. Our current observations suggest that allergen exposure may contribute to poor asthma control by reducing GCR binding affinity in mononuclear cells. This appears to be mediated through IL-2 and IL-4. These findings may have important implications for novel approaches to the treatment of poorly controlled asthma.

Air Pollution, Indoor↗
PubMed1997

Exercise induced bronchospasm in Ghana: differences in prevalence between urban and rural schoolchildren.

BACKGROUND: As more developing countries adopt a westernised style of living, an increase in the prevalence of asthma can be expected to occur in these areas. A study was undertaken to establish the normal response to exercise in Ghanaian children and to use these normal values to determine the prevalence of exercise induced bronchospasm (EIB) in urban rich (UR), urban poor (UP), and rural (R) school children. Skin test reactivity to common inhalant allergens in UR, UP, and R children with and without EIB was also investigated. METHODS: Two hundred children aged 9-16 years without a previous history of respiratory symptoms were randomly selected and underwent free running exercise testing. A normal response to exercise was defined as the group mean change in peak expiratory flow rate (PEFR) +/- 2 standard deviations. This value was used to identify the prevalence of EIB in UR, UP, and R schoolchildren. A total of 1095 children from three different schools underwent exercise testing (220 UP, 599 UR, 276 R), after which 916 children underwent skin prick testing to six common inhalant allergens (D farinae, D pteronyssinus, cat, dog, Aspergillus flavus and Candida albicans). RESULTS: From the results of exercise testing in asymptomatic children the normal range was defined as a fall in PEFR of < 12.5% after exercise. Thirty four children were classified as having EIB on the basis of the above definition, giving an overall prevalence of 3.1%. The prevalence of EIB was significantly higher in UR children (4.7%) than in both UP (2.2%; p < 0.05) and R children (1.4%; p < 0.01). However, the prevalence rates in the UP and R children were similar. The prevalence of atopy in the whole population was 4.4%. Of the children with EIB, 10% were skin test positive to at least one of the allergens tested. The prevalence of atopy was significantly higher in UR children (6.55%, 95% confidence interval (CI) 4.5% to 9.2%) than in UP (2.9%, 95% CI 0.9% to 6.7%) and R children (1.5%, 95% CI 0.4% to 3.7%), respectively (p < 0.005). CONCLUSIONS: The prevalence of EIB and atopy is higher in urban rich than in urban poor or rural children suggesting that, in addition to genetic predisposition, social and environmental factors such as wealth, life style, and housing are important determinants of these phenotypes.

Adolescent↗
PubMed1997

Aerodynamic properties of the major dog allergen Can f 1: distribution in homes, concentration, and particle size of allergen in the air.

Exposure and sensitization to dog allergen is a significant cause of asthma. In this study we investigated the distribution, aerodynamic characteristics, and particle-size distribution of the major dog allergen Can f 1. Dust samples were collected in 50 homes with a dog and 50 homes without dogs. Airborne Can f 1 concentration was measured in 28 homes with dogs and 36 homes without a dog. Particle-size distribution was determined by using 10 separate Andersen sampler measurements in a dog-handling facility, and in 10 homes with dogs, and by repeated measurements in a home with one dog. High levels of Can f 1 (> 10 microg/g) were found in dust in all but one home with a dog and in eight of 50 homes without dogs. Airborne Can f 1 levels varied greatly between the homes with dogs (range: 0.3 to 99 ng/m3). Low levels of airborne Can f 1 (range: 0.4 to 1.1 ng/m3) were detected in 11 of 36 homes without a dog. Can f 1 was predominantly associated with large particles collected on the first stage of the Andersen sampler (> 9 microm), which averaged 42 to 49% of the total allergen recovered in the dog-handling facility and in homes with dogs. Small particles (< 5 microm diameter) also carried Can f 1, and these particles comprised approximately 20% of the total airborne allergen load. There was an excellent concordance between the results obtained in different sampling areas, and between the total Can f 1 recovered on the Andersen sampler and on the parallel filter. In conclusion, airborne Can f 1 was detectable in undisturbed conditions in all homes with dogs and in almost one third of the homes without dogs. In houses with dogs, a significant proportion (approximately 20%) of airborne Can f 1 was associated with small particles (< 5 microm diameter). Owing to their aerodynamic characteristics, these particles would be expected to remain airborne for a long period and, when inhaled, could penetrate into the lower airways and initiate asthma attacks.

Air Pollution, Indoor↗
PubMed1996

Exposure to house dust mite allergens and the clinical activity of asthma.

BACKGROUND: House dust mite allergens play an important role in inducing IgE-mediated sensitization and the development of bronchial hyperresponsiveness (BHR) and asthma. This study investigated the relationship between mite allergen exposure and the clinical activity and severity of asthma. METHODS: Nonsmoking adult patients with asthma (n = 53) were randomly recruited from the asthma registry of two large family practitioner surgeries. Each participant underwent skin testing with common inhalant allergens, a methacholine bronchoprovocation test, and pulmonary function testing on up to 3 separate occasions over a 4-week period. BHR was expressed both as PD20 and dose-response ratio (DRR), and the patients with patients with PD20 of less than 12.25 mumol methacholine were classified as methacholine reactors. Patients were also asked to record peak expiratory flow rate (PEFR) values at 2-hour intervals during waking hours for 1 month. Daily PEFR variability was calculated as amplitude percent mean. Dust samples were collected by vacuuming bedding, bedroom carpets and mattresses. In addition, in the homes of 32 subjects with positive skin test responses to mites, airborne samples were taken overnight for 8 hours with a personal sampler attached to each subject's pillow. Der p 1 and Der p 2 levels were determined by a two-site monoclonal antibody-based ELISA. RESULTS: No difference in mite exposure was found between subjects who were sensitive to mites and those who were not. However, mite-sensitive methacholine reactors were exposed to significantly higher concentrations of Der p 1 in beds than mite-sensitive methacholine nonreactors (13.2 micrograms/gm and 1.45 micrograms/gm, respectively; p < 0.02). Der p 1 and Der p 2 were undetectable in 30 of 32 airborne samples. In mite-sensitive patients both Der p 1 and Der p 2 in beds significantly correlated with BHR (PD20: r = -0.49, DRR, r = 0.49; PD20: r = -0.46, DRR: r = 0.43) and amplitude percent mean PEFR (r = 0.38, r = 0.41) for Der p 1 and Der p 2, respectively. There was a significant negative correlation between exposure to Der p 1 and percent predicted FEV1 (r = -0.43). The correlation between Der p 2 and percent predicted FEV1 just failed to reach a significant level but showed a clear trend ( r = -0.35, p = 0.068). CONCLUSIONS: Clinical activity and severity of asthma (measured by the level of BHR, PEFR variability, and percent predicted FEV1) in mite-sensitive patients is related to exposure to mite allergens in the dust reservoir, with levels in bed being an important indicator that correlated with disease activity.

Adult↗
PubMed1996

Reduction in humidity as a method of controlling mites and mite allergens: the use of mechanical ventilation in British domestic dwellings.

BACKGROUND: Low humidity is an important limiting factor for mite population growth. Reducing humidity can therefore be used as a method to control mites within the home. OBJECTIVE: This study investigated the effect of mechanical ventilation heat recovery (MVHR) units on house dust mites and mite allergen Der p 1 in typical homes in the North-West of England. METHODS: Mite counts and Der p 1 levels were measured at 3-monthly intervals over a period of 1 year in 18 houses (nine with MVHR units and nine architecturally matched control houses). Paired dust samples were collected using a vacuum cleaner with an air-flow rate 451/sec, adapted to collect the sample onto a preweighed filter paper. A 1 m2 area of bedroom carpet, living room carpet and mattress was sampled for 2 min. Indoor temperature and relative humidity (RH) levels were recorded for a period of 1 week before and after the winter period (November and February: 3 and 6 months data sets). The environmental questionnaire was completed at the beginning and at the end of the study. RESULTS: No difference in either Der p 1 concentrations or mite counts in any of the sampling sites at 3, 6, 9 and 12 months as compared with the baseline values was found, both within and between the groups (P > 0.01). The measured levels of RH performed in autumn and winter were found to be lower in the MVHR houses compared to the architectural controls. The indoor temperature during each period did not differ between the groups. Questionnaire data showed that the severity of condensation improved in the MVHR homes, whilst during the winter period, the severity of condensation had increased in the architectural control group. CONCLUSIONS: The MVHR unit does not reduce indoor humidity to levels capable of retarding the mite population growth and decreasing mite allergens in the type of houses predominantly found in the mild and humid climate of the North-West of England.

Allergens↗
PubMed1996

Asthmatic bronchial hyperresponsiveness varies with ambient levels of summertime air pollution.

It is widely believed that the mechanisms of action of outdoor air pollutants are the same as those found in the laboratory, although few studies have attempted to clarify this issue. This study investigates the relationship of asthmatic bronchial hyperresponsiveness (BHR), a marker of airway inflammation, and pulmonary function to ambient levels of summertime air pollution. Thirty eight nonsmoking adult asthmatic subjects underwent repeated measurement of methacholine BHR, using Yan's method, at differing levels of air pollution (O3, SO2, NO2, smoke) during summer 1993. A total of 109 evaluable tests were performed: 31 subjects completed three or more challenge tests, and seven managed two. Levels of all pollutants remained within current World Health Organization (WHO) Guidelines for Health. Changes in BHR were found to correlate significantly with changes in the levels of 24 h mean SO2, NO2 and smoke; 48 h mean NO2 and smoke; 24 h lag NO2; although the effect was only small, accounting for approximately 10% of the variability in within-subject BHR between visits. Twenty four hour lag NO2 was also associated with forced vital capacity (FVC). In conclusion, in subjects with asthma, methacholine bronchial hyperresponsiveness varies with ambient levels of summertime air pollution. This suggests that changes in airway inflammation underlie the increased respiratory morbidity known to accompany pollution episodes.

Adolescent↗
PubMed1996

New mattresses: how fast do they become a significant source of exposure to house dust mite allergens?

BACKGROUND: Sensitization and exposure to mite allergens is a major risk factor for asthma. Little is known about the rate of build-up of allergens in the mite micro-habitats. OBJECTIVES: To investigate the rate of increase in mite allergen levels in new mattresses. METHODS: Der p 1 was measured in the dust samples collected from six identical new single mattresses over a period of 2 years. RESULTS: Der p 1 increased significantly at 4 months as compared with baseline level (P < 0.01), but no difference was found between the concentrations at 4, 8, 12 and 24 months. There was a significant correlation between Der p 1 concentration in mattresses at 4, 8, 12 and 24 months and Der p 1 levels in the bedroom carpet at the beginning of the study. CONCLUSIONS: New mattresses can become a significant source of exposure to mite allergens after a short period of time (< 4 months). There is little justification for advising mite sensitive patients to replace their mattresses as a part of avoidance regime.

Allergens↗
PubMed1996

Domestic allergens in public places. II: Dog (Can f1) and cockroach (Bla g 2) allergens in dust and mite, cat, dog and cockroach allergens in the air in public buildings.

BACKGROUND: Sensitization and exposure to indoor allergens are the major risk factors for asthma. It is possible that significant exposure to domestic allergens occurs outside the home. OBJECTIVES: To investigate the levels of Can f 1 and Bla g 2 in the dust from carpeted floors and upholstered seats in public buildings and public transport and the airborne concentrations of Der p 1, Fel d 1, Can f 1 and Bla g 2 in schools and offices. METHODS: Can f 1 and Bla g 2 were measured in the dust collected by vacuuming a 1 m2 area of carpet, as well as upholstered seats in five schools, six hotels, four cinemas, six pubs, three buses and two trains. Dust was also collected from the bedroom carpet, living room carpet, mattress and sofa in 20 homes with and 20 homes without a dog in the same area. Personal airborne sampling (2 L/min) was conducted for 8 h in offices (n = 16) and classrooms (n = 9). In addition, airborne samples in schools were collected using a high volume pump (60 L/min) for 1 h in three classrooms immediately after the children vacated the school. Can f 1, Bla g 2, Der p 1 and Fel d 1 were assayed using a two-site monoclonal antibody-based ELISA. RESULTS: Can f 1 was detected in all dust samples from public places, ranging from 0.2 to 52.5 micrograms/g. Significantly higher levels were found in upholstered seats (geometric mean--GM 9.4 micrograms/g) than in carpets (GM 1.5 micrograms/g; P < 0.001), and levels of Can f 1 > 10 micrograms/g were found in 40% of upholstered seats in public places. Can f 1 was significantly higher in upholstered seats in public places than in sofas in homes without a dog (GM 1.8 micrograms/g; P < 0.001). Detectable levels of Bla g 2 were found in all of the schools (GM 2.4 U/g, range 0.8-4.4 U/g). Bla g 2 concentration greater than 2U/g (provisional threshold level representing risk of sensitization) was measured in 65% of the classrooms sampled. Der p 1 and Bla g 2 were below the detection limit in all airborne samples. However, airborne Fel d 1 and Can f 1 were detected in schools and offices, albeit in low concentrations. CONCLUSIONS: Upholstered seats from public places constitute a reservoir for the accumulation of dog allergen, and a source of exposure to Can f 1 inside public buildings or on public transport. Exposure to cockroach allergens in schools may be important for cockroach sensitized asthmatic children.

Air Pollution, Indoor↗
PubMed1995

Portable dehumidifiers in the control of house dust mites and mite allergens.

Humidity is a decisive limiting factor for house dust mite (HDM) population growth and decreasing humidity may be the control method of choice. This study investigates the effects of portable dehumidifiers on the mite counts and concentration of the HDM allergen Der p I in the homes in northwest England. Mite counts and Der p I were measured in the paired dust samples collected by vacuuming a 1 m2 area of bedroom carpet, living room carpet, mattress and sofa for 2 min in six houses supplied with the dehumidifier and six control houses, before and 1, 2 and 3 months after the installment of dehumidifier. Temperature and relative humidity were recorded daily. There was no difference in mite counts in either of the groups throughout the study. Der p I decreased significantly in both groups and in all sampling sites, but no significant differences in the levels of reduction between the groups were found. Condensation was decreased in the dehumidifier group, but the level of indoor humidity capable of retarding mite population growth was not achieved. A single portable dehumidifier placed centrally in the house is unable to decrease indoor humidity to the level capable of retarding mite population growth and decreasing HDM allergens in the type of houses predominantly found in the northwest of England.

Allergens↗
PubMed1994

House dust mite and cat allergen in different indoor environments.

Allergy to house dust mites (HDM) and domestic pets is a major cause of asthma. People in developed countries spend more than 90% of their time indoors. We have measured levels of HDM allergen Der pI and cat allergen Fel dI in public buildings and public transport. Dust samples were collected by vacuuming a 1 m2 area for 2 min from five schools, six hotels, four cinemas, six pubs, three buses, two trains and 12 domestic households without a cat. Der pI and Fel dI were assayed with monoclonal antibodies in a two-site immunometric ELISA. Der pI concentration was significantly higher in the private homes than in comparable sites in public places except for cinema seats (where high values were found) compared with domestic sofas. Der pI > 2000 ng/g of fine dust was found in 30% of the upholstered seats, 9% having a concentration > 10,000 ng/g. Fel dI levels were significantly higher in the dust from upholstered seats (geometric mean 14.88 micrograms/g) than in carpeted floors (geometric mean 0.73 micrograms/g), and in public places than in private homes. Fel dI > 8 micrograms/g was found in 79% of the upholstered seats or furniture sampled in public buildings or public transport. In conclusion, upholstered seats from public buildings and public transport constitute an allergen reservoir for continuous contamination of the indoor environment which could compromise the effects of allergen avoidance employed at home.

Air Pollutants↗
PubMed1994

Exercise testing revisited. The response to exercise in normal and atopic children.

BACKGROUND: Wide differing criteria are used to define the normal airway response to exercise, and as a consequence the estimated incidence of exercise-induced bronchospasm (EIB) in atopic children is wide. The purpose of this study was to establish normal range for changes in spirometry after exercise in children and then to use these normal values to assess the incidence of EIB in atopic children. METHODS: Pulmonary function was assessed before, and 2, 5, and 10 min after 6 min of free running exercise in a group of 48 normal and 96 atopic children (70 asthmatics, 17 with allergic rhinitis, and 9 with atopic dermatitis/food hypersensitivity). RESULTS: The EIB (defined as the normal group mean value -2 SD) occurred with a > 10 percent fall in FEV1, > 17.5 percent fall in peak expiratory flow rate (PEFR), > 26 percent fall in mean forced expiratory flow during the middle half of the forced vital capacity (FEF25-75), and > 40 percent fall in FEF25. Sixty-three of 70 asthmatic patients had EIB by at least one of these definitions, most marked at 5 min postexercise. The combination of FEV1 and FEF25-75 criteria enabled detection of all subjects with EIB. By FEV1 and FEF25-75 criteria, none of the subjects with allergic rhinitis or dermatitis had EIB. The fall in FEV1 after exercise in children with allergic rhinitis was within the range of normal, but with a significantly lower mean value than control subjects. CONCLUSIONS: EIB should be defined by using more than one maximum expiratory flow-volume curve parameter (ie, FEV1 and FEF25-75). The EIB (defined as a fall in FEV1 and FEF25-75) was only seen in asthmatic children and not in other atopic groups.

Adolescent↗
PubMedDate not supplied

Allergen avoidance.

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Air Conditioning↗