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Daycare centers: are indoor allergen levels important?
Guest editorial
Daycare centers: are indoor allergen levels important? Allergen avoidance plays a significant role in the management of patients with atopic disease. Despite improvements in the understanding of inflammatory mechanisms, allergen identification, and disease management, the prevalence and severity of asthma and other allergic syndromes have continued to increase over the past decades.1 The underlying etiology for this increase remains elusive but is likely multifactorial. Exposure in early childhood is a well established risk for allergen sensitization and the development of asthma. The importance of the indoor environment is now well recognized, and the allergen content in several environments is under study.2–5 Many factors contribute to the quality of the indoor environment making its analysis a difficult area of study. Socioeconomic status, indoor and outdoor climates, individual lifestyles and characteristics, hygiene, and other factors yet to be recognized likely play a role in indoor allergen content and exposure. It is important to point out that ⬎50% of preschool aged children now attend daycare centers, a significant increase compared with past decades. Is the quality of the daycare environment important for a child spending nearly half the day in this environment? Is exposure of the immature immune system to allergen in the daycare environment as important as exposure in the home environment? We have few answers to this question. In the study published in this issue of the Annals, Ferna´ndez-Caldas et al6 report high levels of indoor allergens in daycare settings in the warm and humid southeastern United States. Dust mite levels ranging from 10 to 1,200 mites/gram
VOLUME 87, SEPTEMBER, 2001
of dust were found in 75% of the daycare centers tested. The mite allergens, Der p 1 and Der f 1, were found in concentrations up to 21.8 g and 2.1 g/g of dust, respectively, and 40% of the daycare centers studied had mite allergen levels ⬎2 g/g of dust. Exposure to dust mite allergen concentration of 2 g/g of settled dust is recognized as a risk for sensitization, and concentrations ⬎10 g/g of dust have been associated with asthma exacerbations in sensitized individuals.7 Although the allergen concentration associated with sensitization and the development of asthma has been established for dust mite, levels of allergen required for sensitization is less well understood for other indoor allergens. The group 1 cockroach allergens Bla g 1 and Per a 1 are cross-reactive and have 72% sequence identity. Exposure to high levels of cockroach allergen, defined as 8 U/g of dust, has been associated with emergency department visits and hospital admissions.8 –10 Cockroach allergen in a concentration as low as 2 U/g of settled dust has been proposed as the threshold level for sensitization.11 Although the highest levels of cockroach allergen are detected in kitchen dust samples, sensitization until now has correlated best with allergen exposure in the bedroom.12 Dust samples from the daycare centers in the current study reveal levels of the cockroach allergen Per a 1 as high as 1.8 g/g of dust. What allergen concentration in the daycare or playroom environment is sensitizing? A concentration of the major cat allergen Fel d 1 of 1 to 2 g/g of dust has been associated with sensitization, and air sample levels as low as 100 ng/m3 are capable of inducing asthma symptoms and pulmonary function chang-
es.7,13 Although there is no mention of pet exposure in the daycare environment, it is well known that the physical presence of a cat in the environment or direct feline exposure is not required for sensitization. Dust samples in the study revealed levels of Fel d 1 as high as 120 U/g of dust. A paucity of data is currently available with regard to the quality of the indoor daycare environment. At a time when the prevalence and severity of allergic disease are on the rise, it may be important to determine the level of allergen exposure in this relatively new environment. It would be of interest to know the levels of cat allergen in air samples, as well as from walls and surfaces of the daycare centers, as the distribution characteristics of cat allergen differ from those of mites and cockroaches. Knowledge of the specific characteristics of the daycare centers would be helpful in establishing guidelines for allergen avoidance. For example, of the 20 daycare centers studied, 4 had linoleum flooring whereas 16 had wall-to-wall carpeting. Humidity levels may have been helpful in determining its significance in mite allergen levels. The home environment history of the children attending the daycare centers might also be interesting to know. How many children who have furred indoor pets at home attend the centers? With regard to the daycare centers, were dust-collectibles present, such as stuffed toys and upholstered furniture? Were the areas for eating separate from the playroom area? This study’s aim, to determine allergen levels in the daycare environment, is an important initial step. Further investigation of this important locale is needed to determine the level of allergen exposure in an environment that
175
has until now been largely overlooked. With a better understanding of the environmental characteristics of the locations where children spend the majority of their time, relatively simple measures might be instituted to control the indoor environment.14 LAURIANNE G. WILD, MD and MANUEL LOPEZ, MD Section of Clinical Immunology and Allergy Department of Medicine Tulane University Health Sciences Center New Orleans, LA REFERENCES 1. Yunginger JW, Reed CE, O’Connell EJ, et al. A community-based study of the epidemiology of asthma: incidence rates, 1964 –1983. Am Rev Respir Dis 1992:146:888 – 894. 2. Warner AM, Bjo¨rkste´n B, Munir AK, et al. Childhood asthma and exposure to indoor allergens: low mite levels are associated with sensitivity. Pediatr Allergy Immunol 1996;7:61– 67.
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3. Sarpong SB, Woo RA, Karrison T, Eggleston PA. Cockroach allergen (Bla g 1) in school dust. J Allergy Clin Immunol 1997;99:486 – 492. 4. Dornelas de Andrade A, Charpin D, Birnbaum J, et al. Indoor allergen levels in day nurseries. J Allergy Clin Immunol 1995;95:1158 –1163. 5. Zhang L, Chew FT, Soh SY, et al. Prevalence and distribution of indoor allergens in Singapore. Clin Exp Allergy 1997;27:876 – 885. 6. Ferna´ndez-Caldas E, Codina R, Ledford DK, et al. House dust mite, cat, and cockroach allergen concentrations in daycare centers in Tampa, Florida. Ann Allergy Asthma Immunol 2001; 87:196 –200. 7. Platts-Mills T, Vervloet D, Thomas W, et al. Indoor allergens and asthma: report of the Third International Workshop. J Allergy Clin Immunol 1997; 100:S2–S24. 8. Chapman MD, Vailes LD, Hayden ML, et al. Cockroach allergens and their role in asthma. In: Kay AB, editor. Allergy and Allergic Diseases. Oxford, UK: Blackwell Science Ltd, 1996:942–951. 9. Gelber LE, Seltzer LH, Bouzoukis JK, et al. Sensitization and exposure to in-
10.
11.
12.
13.
14.
door allergens as a risk factors for asthma among patients presenting to hospital. Am Rev Respir Dis 1993; 147:573–578. Call RS, Smith TF, Morris E, et al. Risk factors for asthma in inner-city children. J Pediatr 1992;121: 862– 866. Huss K, Adkinson NF Jr, Eggleston PA, et al. House dust mite and cockroach exposure are strong risk factors for positive allergy skin test responses in the Childhood Asthma Management Program. J Allergy Clin Immunol 2001;107:48 –54. Rosenstreich DL, Eggleston PA, Kattan M, et al. The role of cockroach allergy and exposure to cockroach allergen in causing morbidity among inner-city children with asthma. N Engl J Med 1997;336:1356 –1362. Bollinger ME, Eggleston PA, Wood RA. Cat antigen in homes with and without cats may induce allergic symptoms. J Allergy Clin Immunol 1996;97:907–914. Htut T, Higenbottam TW, Gill GW, et al. Eradication of house dust mite from homes of atopic asthmatic subjects: a double-blind trial. J Allergy Clin Immunol 2001;107:55– 60.
ANNALS OF ALLERGY, ASTHMA, & IMMUNOLOGY
Daycare centers: are indoor allergen levels important? Allergen avoidance plays a significant role in the management of patients with atopic disease. Despite improvements in the understanding of inflammatory mechanisms, allergen identification, and disease management, the prevalence and severity of asthma and other allergic syndromes have continued to increase over the past decades.1 The underlying etiology for this increase remains elusive but is likely multifactorial. Exposure in early childhood is a well established risk for allergen sensitization and the development of asthma. The importance of the indoor environment is now well recognized, and the allergen content in several environments is under study.2–5 Many factors contribute to the quality of the indoor environment making its analysis a difficult area of study. Socioeconomic status, indoor and outdoor climates, individual lifestyles and characteristics, hygiene, and other factors yet to be recognized likely play a role in indoor allergen content and exposure. It is important to point out that ⬎50% of preschool aged children now attend daycare centers, a significant increase compared with past decades. Is the quality of the daycare environment important for a child spending nearly half the day in this environment? Is exposure of the immature immune system to allergen in the daycare environment as important as exposure in the home environment? We have few answers to this question. In the study published in this issue of the Annals, Ferna´ndez-Caldas et al6 report high levels of indoor allergens in daycare settings in the warm and humid southeastern United States. Dust mite levels ranging from 10 to 1,200 mites/gram
VOLUME 87, SEPTEMBER, 2001
of dust were found in 75% of the daycare centers tested. The mite allergens, Der p 1 and Der f 1, were found in concentrations up to 21.8 g and 2.1 g/g of dust, respectively, and 40% of the daycare centers studied had mite allergen levels ⬎2 g/g of dust. Exposure to dust mite allergen concentration of 2 g/g of settled dust is recognized as a risk for sensitization, and concentrations ⬎10 g/g of dust have been associated with asthma exacerbations in sensitized individuals.7 Although the allergen concentration associated with sensitization and the development of asthma has been established for dust mite, levels of allergen required for sensitization is less well understood for other indoor allergens. The group 1 cockroach allergens Bla g 1 and Per a 1 are cross-reactive and have 72% sequence identity. Exposure to high levels of cockroach allergen, defined as 8 U/g of dust, has been associated with emergency department visits and hospital admissions.8 –10 Cockroach allergen in a concentration as low as 2 U/g of settled dust has been proposed as the threshold level for sensitization.11 Although the highest levels of cockroach allergen are detected in kitchen dust samples, sensitization until now has correlated best with allergen exposure in the bedroom.12 Dust samples from the daycare centers in the current study reveal levels of the cockroach allergen Per a 1 as high as 1.8 g/g of dust. What allergen concentration in the daycare or playroom environment is sensitizing? A concentration of the major cat allergen Fel d 1 of 1 to 2 g/g of dust has been associated with sensitization, and air sample levels as low as 100 ng/m3 are capable of inducing asthma symptoms and pulmonary function chang-
es.7,13 Although there is no mention of pet exposure in the daycare environment, it is well known that the physical presence of a cat in the environment or direct feline exposure is not required for sensitization. Dust samples in the study revealed levels of Fel d 1 as high as 120 U/g of dust. A paucity of data is currently available with regard to the quality of the indoor daycare environment. At a time when the prevalence and severity of allergic disease are on the rise, it may be important to determine the level of allergen exposure in this relatively new environment. It would be of interest to know the levels of cat allergen in air samples, as well as from walls and surfaces of the daycare centers, as the distribution characteristics of cat allergen differ from those of mites and cockroaches. Knowledge of the specific characteristics of the daycare centers would be helpful in establishing guidelines for allergen avoidance. For example, of the 20 daycare centers studied, 4 had linoleum flooring whereas 16 had wall-to-wall carpeting. Humidity levels may have been helpful in determining its significance in mite allergen levels. The home environment history of the children attending the daycare centers might also be interesting to know. How many children who have furred indoor pets at home attend the centers? With regard to the daycare centers, were dust-collectibles present, such as stuffed toys and upholstered furniture? Were the areas for eating separate from the playroom area? This study’s aim, to determine allergen levels in the daycare environment, is an important initial step. Further investigation of this important locale is needed to determine the level of allergen exposure in an environment that
175
has until now been largely overlooked. With a better understanding of the environmental characteristics of the locations where children spend the majority of their time, relatively simple measures might be instituted to control the indoor environment.14 LAURIANNE G. WILD, MD and MANUEL LOPEZ, MD Section of Clinical Immunology and Allergy Department of Medicine Tulane University Health Sciences Center New Orleans, LA REFERENCES 1. Yunginger JW, Reed CE, O’Connell EJ, et al. A community-based study of the epidemiology of asthma: incidence rates, 1964 –1983. Am Rev Respir Dis 1992:146:888 – 894. 2. Warner AM, Bjo¨rkste´n B, Munir AK, et al. Childhood asthma and exposure to indoor allergens: low mite levels are associated with sensitivity. Pediatr Allergy Immunol 1996;7:61– 67.
176
3. Sarpong SB, Woo RA, Karrison T, Eggleston PA. Cockroach allergen (Bla g 1) in school dust. J Allergy Clin Immunol 1997;99:486 – 492. 4. Dornelas de Andrade A, Charpin D, Birnbaum J, et al. Indoor allergen levels in day nurseries. J Allergy Clin Immunol 1995;95:1158 –1163. 5. Zhang L, Chew FT, Soh SY, et al. Prevalence and distribution of indoor allergens in Singapore. Clin Exp Allergy 1997;27:876 – 885. 6. Ferna´ndez-Caldas E, Codina R, Ledford DK, et al. House dust mite, cat, and cockroach allergen concentrations in daycare centers in Tampa, Florida. Ann Allergy Asthma Immunol 2001; 87:196 –200. 7. Platts-Mills T, Vervloet D, Thomas W, et al. Indoor allergens and asthma: report of the Third International Workshop. J Allergy Clin Immunol 1997; 100:S2–S24. 8. Chapman MD, Vailes LD, Hayden ML, et al. Cockroach allergens and their role in asthma. In: Kay AB, editor. Allergy and Allergic Diseases. Oxford, UK: Blackwell Science Ltd, 1996:942–951. 9. Gelber LE, Seltzer LH, Bouzoukis JK, et al. Sensitization and exposure to in-
10.
11.
12.
13.
14.
door allergens as a risk factors for asthma among patients presenting to hospital. Am Rev Respir Dis 1993; 147:573–578. Call RS, Smith TF, Morris E, et al. Risk factors for asthma in inner-city children. J Pediatr 1992;121: 862– 866. Huss K, Adkinson NF Jr, Eggleston PA, et al. House dust mite and cockroach exposure are strong risk factors for positive allergy skin test responses in the Childhood Asthma Management Program. J Allergy Clin Immunol 2001;107:48 –54. Rosenstreich DL, Eggleston PA, Kattan M, et al. The role of cockroach allergy and exposure to cockroach allergen in causing morbidity among inner-city children with asthma. N Engl J Med 1997;336:1356 –1362. Bollinger ME, Eggleston PA, Wood RA. Cat antigen in homes with and without cats may induce allergic symptoms. J Allergy Clin Immunol 1996;97:907–914. Htut T, Higenbottam TW, Gill GW, et al. Eradication of house dust mite from homes of atopic asthmatic subjects: a double-blind trial. J Allergy Clin Immunol 2001;107:55– 60.
ANNALS OF ALLERGY, ASTHMA, & IMMUNOLOGY