United States Environmental Protection Agency »EPA Off ice Of The Administrator (A101F) EPA171-R-92-016 PB-92-182419 1992 A Study Of House Dust Mites And Cat Dander In The Office Enviroment Printed on Recycled Paper ------- A Study of House Dust Mites and Cat Dander in The Office Environment Stacey J. Baker Francis Dougherty (Project Officer) August 28,1991 U.Si Enyirofcmentai Protection Pcni'tfa 5, Library (PL-12J) ••7\V^t JacksC'3 Bcu!-, .% j ------- DISCLAIMER This report was furnished to the U.S. Environmental Protection Agency by the student identified on the cover page, under a National Network for Environmental Management Studies fellowship. The contents are essentially as received from the author. The opinions, findings, and conclusions expressed are those of the author and not necessarily those of the U.S. Environmental Protection Agency. Mention, if any, of company, process, or product names is not to be considered as an endorsement by the U.S. Environmental Protection Agency. ------- This paper is the result of a joint project between the United States Environmental Protection Agency and the United States Public Health Service and will become part of a future journal article. Individuals who took part in the project and writing of this paper are as follows: United States Environmental Protection Agency: Stacey Jill Baker Francis Dougherty United States Public Health Service Chin S. Yang, Ph.D. Ling Ling Hung, Ph.D. Frank Lewis ------- Literature Review House dust mites and cat dander have both been known to induce allergic responses and asthmatic attacks in many individuals. Many researchers have conducted studies which concern these allergens in the home; however, few studies have assessed the "working" or "office" environment in the United States. As a result, this study concentrates on the presence of house dust mites and cat dander in large office buildings in the eastern United States- There are two species of Dermatophagoides that are most commonly found in the home and are frequent sources of house dust allergy: Dermatophagoides pteronyssinus and D. farinae (1-19). As their name indicates, the main diet of these microscopic organisms is human skin scales; hence, they are frequently found in "high use areas" where there is a great deal of human presence and activity (2, 6,8- 12,20,21). In addition to the above nutritional requirement, the Dermatophagoides spp. also require proper humidity and temperature for survival and maintenance of homeostasis. Former studies have stated that humidity is a key factor in controlling mite breeding and numbers (2,4-6,8-14,18,20,22,23-32). Although humidity is difficult to control (6), it remains a crucial tool for controlling mite populations. The microenvironment of these mites contains no liquid water (12); if an absolute indoor humidity of 7g/kg (2,6,8) (equivalent to a relative humidity of 60% at 70°F) (2) is not maintained, water loss and subsequent dehydration can occur. The use of air-conditioners not only lowers room temperatures, but also the indoor humidity by removing water form the air (6,8). Thus, areas that are air-conditioned generally harbor fewer mites than those areas without an air-conditioning system; in one study, mite numbers were reduced by a factor of ten (33). (This is not to say, ------- however, that mite allergen levels will drop with the use of air-conditioning if mite feces is present in the environment). Due to the fact that humidity is so important for mite survival, mite growth has been correlated with seasonal variations in temperate regions around the world (5,6,8,10,12,21,24,25,30); for example, in North America, mite growth has reached maximum levels in the summer months when the humidity is the highest (2,26). As aforementioned, temperature is another important factor in maintaining house dust mite populations. Temperatures that are either too high or too low can affect mites. The life cycle from egg to adult for both D. pteronyssinus and D. farinae is approximately 23-30 days; the duration of this cycle can be shortened by higher and lengthened by lower temperatures (12). Optimal temperature for growth is within the range of 17-25°C (25). Environmental conditions, humidity in particular, also influence the particular species of mite that dominates in the home to some degree. Homes with lower indoor humidity usually contain predominantly D. farinae whereas it appears that D. pteronyssinus requires higher humidity for survival (1-3, 6,12,18,2432). In addition to the climate of the actual room, the microclimate which is provided by carpets and upholstery of furniture is also important. Long pile carpets contain more mites than short pile carpets, and the latter contain more than un- carpeted (tile of wood) floors. Apparently, long pile carpets are able to accumulate and maintain adequate food supplies as well as adequate climactic conditions needed to sustain a mite population (10,12,22). It is also important to note that vacuuming of long pile carpets does not allow full removal of mite bodies and feces that are present. Vacuuming merely removes a fraction of what is present, ------- Allergens from particularly the surface dust, as has been determined by studies that yielded equal amounts of dust and .llergens after repeated vacuumings (8,10,12,28). the Dermatophagoides species of mite are classified into two groups: Group I (Der J> I and Der f I) and Group U (Der p H and Der f H) allergens. The first purified grout) of allergens, Group I, have a molecular weight of 25,000 and are characterized as glycoproteins (2,25). Both Der p I ( a cysteine protease) (34) and Der f I display cross reactivity, structural homology, and are associated with mite feces that are carried 01 pa-tides greater than 10 um in diameter (2,6-8,25,35). Due to their large size, the amount of airborne allergen is small (immeasurable in some studies) unless the roo n is disturbed; in this particular case, allergen (and particle) levels rise with disturb making), and then fall fall within a five minu house dust mites may (36). The Group II alle with the whole body oi ance (i.e. human activities such as vacuuming and bed- quickly. Certain studies have shown that these large particles :e time period. Hence, many individuals who are allergic to only experience symptoms upon entering a disturbed room •gens have a molecular weight of 15,000 and also display dose structural homology and cross-reactivity (25). Der p H and Der f H are associated the mite (7); in addition, a study conducted by Sakaguchi et. al. (7) has suggested th^t Der H allergens are less prone to float that the Der I allergens. Unlike the allergens of the above mentioned house dust mites, the major cat allergen, Pel d I, tends :o remain airborne for longer periods of time with or without disturbance due to the :act that this particular allergen is carried on partides less than 2.5 um in diamet jr. Hence, while those individuals who are sensitive to house dust mites may Experience little discomfort in an undisturbed setting, those who are allergic to cats Lay experience a rapid onset of asthmatic and allergic ------- symptoms in an identical undisturbed environment. Even after disturbance, these smaller particles can remain airborne for many hours (35). Pel d I, with a molecular weight of 37,000 is characterized as an acidic salivary protein; thus, the main source of this allergen is probably saliva. Nevertheless, further crossed radio-immunoelectrophoresis (CRIE) analysis shows that Pel d I is a dander (superficial skin material) related component. It is also important to note that cat hair has been used to obtain the most complete cat allergen extract (37). Due to the fact that most cats shed quite often, the feline does not have to be present in order to induce an allergic response. It is a reasonable assumption that those individuals who own a cat serve as carriers for the allergen throughout areas where a cat has not been found. In conclusion, allergies to common house dust are common due to the numerous amount of allergens that are carried on dust particles. Both Dermatophagoides spp. and cat allergens have been identified as major allergens. Due to the high number of individuals who are allergic to the substances, a study involving their role in the office building environment is considered. ------- Introduction House dust mites and cat dander have both been known to induce asthmatic attacks and allergic responses in many individuals . There have been many studies regarding the major allergens from house dust mites and cats in the homed-3,5- 8,13,24-26,34-37,39-41); however, few studies have been conducted regarding these allergens in the office environment. This study surveys the presence of house dust mites and cat dander in large office buildings. Materials and Methods Five office buildings (two located in Philadelphia, Pennsylvania; three located in Washington D.C.) were visited during the first two weeks of August; each building was selected on the basis of previously obtained indoor air information and accessibility. Ten sites were randomly chosen in each building and sampled in the following manner: approximately, a square meter area of carpet was vacuumed with a vacuum cleaner (Hoover Legacy, model 810) for one minute ( to avoid extreme noise disturbance in a working office environment) with the aid if an indoor allergen collection device supplied by ALK laboratories. This device fits onto the hose of a conventional vacuum. Temperature, relative humidity, and carbon dioxide were also measured at the time of collection. At five of the ten sites in each building, the entire surface area of an upholstered chair was sampled in addition to the carpet (bringing the total number of samples in each building to fifteen). In addition to the above, a questionnaire was distributed to approximately five individuals at each sampling site. (A sample copy is attached). ------- All samples were kept in their original collection containers and sealed in food storage bags until the final analysis (performed 1-2 weeks after collection). The samples were sent to ALK laboratories for immunochemical analysis which measured the concentrations of house dust mite and cat allergens: Der p I, Der f I, and Pel d I by the ELISA method. The questionnaires used in this study were tabulated. Information such as the percentage of individuals who are allergic to dust mites and cat dander, and the percentage of individuals who own cats was obtained. Results and Discussion A total of 75 samples and 211 questionnaires were collected from 50 sites in 5 office buildings. Although the total laboratory data has not yet become available, statistical results were obtained from the questionnaires (Table 1). The table shows the number and percentage of individuals in each building who are allergic to house dust mites and cat dander; the number and percentage of individuals who may be allergic to cat dander; the number and percentage of individuals who own cats; and the total number of cats. When the individual numbers and percentages are combined, the study reveals that 16.11% of the individuals have been diagnosed as being allergic to house dust mites and that 8.05% of the individuals have been diagnosed as being allergic to cat dander. However, twenty-five of the questioned individuals feel that they are possibly allergic to cat dander; if these individuals are included, the ------- 8 percentage of individuals allergic to cat dander increases to almost 20%. Hence, according to this study, 1 out of 5 individuals is potentially allergic to cat dander. It has been stated in a previous study conducted by Luczynska et. al. (35) that 28% of American homes own at least one cat. The numbers generated by this particular study show that 21.3%, or approximately one out of every five individuals owns a cat. Hence, according to this preliminary study, roughly equal percentages of the population own a cat or are allergic to cat dander. The portion of laboratory data which has become available is shown on tables 2-6. It is important to note the areas which contain moderate to high concentrations of allergens; all but one of these areas contain no questioned individuals who spoke of allergic reactions in the working environment. Guidelines concerning levels of Der p I, Der f I, and Pel d I are as follows (21,38-40): Per p I and Per f I Less than 2ug/g dust LOW 2 to lOug/g dust MODERATE (risk of development of asthma) (2ug/g equals approximately 100 mites/g dust) Greater than lOug/g dust HIGH (risk for acute asthmatic attack) (lOug/g equals approximately 500 mites/g dust) Pel d I Less than lug/g dust LOW 1 to 8 ug/g dust MODERATE (may be risk factor for sensitization to cats) Greater than 8 ug/g dust HIGH (risk factor for acute asthma) ------- It has been previously stated that humidity is a crucial tool which controls mite populations; in addition, by removing water from the air, air-conditioning has been known to reduce mite populations. All of the areas sampled in this study are air- conditioned. Although microscopic counts have not yet been performed, it is thought that the air-conditioning may have controlled mite numbers in areas where little or no mite allergen was found. Obviously, further laboratory analysis is needed to confirm this possible conclusion. Optimal growth conditions for house dust mites is 70°F with a relative humidity of 70% (2). None of the areas whose data has been made available had a relative humidity greater than 66%. However, as the tables show, many areas have temperatures at or greater than 70°F, relatively suitable for mites. None of the 50 sampled sites whose laboratory data is available contained high concentrations of Der p I allergen. However, two of the sites did contain high levels of Der f I. The questionnaires from these areas showed that two individuals were diagnosed as being allergic to house dust mites. In fact, one individual in one of these areas complained of allergic responses in the working environment. These responses may indicate that house dust mites may be present in offices and able to induce allergic symptoms. Further studies are needed to test the validity of this statement. There were four sites which had high concentrations of Pel d I: 11.4 ug/g, 13.8 ug/g, 16.7 ug/g, and 30.7ug/g. The number of cats whose allergens could potentially be carried into these office areas are: 0,8,7,and 1 respectively. These results may show, like those of previous studies (41), that the cat need not be present for cat allergens to appear in the environment. This phenomenon is due to the fact ------- 10 that cat allergens are carried on dust particles less that 2.5 urn in diameter (35,36); these particles float easily and may be carried by humans into other areas. The above are the preliminary results of this study regarding house dust mites and cat dander in the office environment. Further studies are needed to substantiate the data generated from this study. ------- Table 1 Building Building 1 Building 2 Building 3 Building 4 Building 5 Individuals Questioned 43 49 39 35 45 Dust Mite Allergic Individuals 9 8 5 2 10 % Allergic to Dust Mites 20.9 16.32 12.8 5.71 22.2 Cat Dander Allergic Individuals 3 5 3 1 5 % Allergic to Cat Dander 6.9 10.2 7.69 2.85 11.11 Individuals Who May Be Allergic to Cat Dander 9 8 4 4 3 % May Be Allergic to Cat Dander 20.93 16.32 23.07 11.42 6.66 Individuals with Cats 1 2 9 9 1 2 3 % With Cats 27.9 18.36 23.07 34.28 6.66 ------- Table 2- Building 1 Sample Der pi Der f I Pel d T rr* T rei d i C02 Temperature Relative (ppm) (Fahrenheit) Humidity 01 02 03 04 05 06 07 08 09 1 0 1 1 12 13 14 15 0-1 0.1 0.9 450 0.2 0.4 6.1 450 O.Ob O.Ob 30.7 550 0-1 O.Ob 1.1 450 O.Ob O.Ob 0.7 450 * * 500 550 O-1 0.5 16.7 500 500 * * * * 450 0.1 6.9 0.1 450 °-1 15.4 O.Ob 400 °-0b 0.6 O.Ob 450 O.Ob 0.2 0.7 450 O.Ob 0.1 0.2 350 76 76 74 72 72 77 78 77 78 72 72 73 72 72 75 38 38 48 46 46 39 48 ' 39 39 50 50 48 48 48 40 * Data not yet available b Below detection limit ------- Table 3- Building 2 Sample Der p I Der f I Fel d I CO2 Temperature Relative (ppm) (Fahrenheit) Humidity 01 02 03 04 05 06 07 08 09 10 1 1 12 13 14 15 * * * O.Ob 0.3 0.4 * * * 0.1 0.1 1.4 * * * * * * * * * 0.1 0.4 0.4 0.1 O.Ob 0.1 * * * O.Ob 0.1 13.8 * * * * * * * * * 0.1 0.3 11.4 550 550 450 450 500 500 550 550 500 600 600 550 450 650 650 77 77 75 75 74 75 78 78 79 77 77 76.5 72.5 69 69 48 48 47 47 50 47 48 48 50 45 45 45 47 50 50 * Data not yet available b Below detection limit ------- Table 4- Building 3 Sample Der p I Der f I Pel rf T rrv. T F i rei d I O02 Temperature Relative (ppm) (Fahrenheit) Humidity 01 02 03 04 05 06 07 08 09 10 1 1 12 13 14 15 550 600 600 350 °-1 O.Ob O.Ob 450 °-6 0.5 0.3 450 * * * * 600 * * * * 400 °'1 0.1 0.2 500 °'6 1-5 1.0 500 °'1 2.5 0.3 500 °-6 2.9 0.7 500 * * * * 450 0-7 3.0 0.4 450 0.2 4.6 0.2 550 73 74 74 72 72 72 72.5 71 73 73 76 76 72.5 72.5 72 57 54 54 60 57 57 57 61 46 46 42 42 47 47 52 * Data not yet available b Below detection limit ------- Table 5- Building 4 Sample Der p I Der f I Pel d I C02 Temperature Relative (ppm) (Fahrenheit) Humidity 01 02 03 04 05 06 07 08 09 10 1 1 12 13 14 15 * 2.4 * * 0.7 * * 0.1 0.1 * 0.1 * 0.1 O.Ob * * 0.7 * * 0.5 * * 2.1 0.5 * 0.4 * 0.4 0.1 * * 7.3 * * 0.5 * * 2.4 O.Ob * 0.8 * 0.3 0.5 * 350 350 300 400 400 350 350 350 400 400 400 400 400 350 300 71 71 72 70,5 70.5 74 71 71 73.5 73 73 76 76 74 67.5 64 64 60 60 64 64 64 64 57 59 59 54 54 54 64 * Data not yet available b Below detection limit ------- Table 6- Building 5 Sample Der pi Der f I Pel d I rrv, T, ™ a i UJ2 Temperature Relative (ppm) (Fahrenheit) Humidity 01 02 03 04 05 06 07 08 09 10 1 1 12 13 14 15 * * * * 350 0.1 0.1 0.2 350 * * * * 550 * * * * 550 °-0b 0-3 0.1 600 °'2 1-2 0.4 600 * * * * 550 °'4 0-3 0.7 550 O.Ob 6.8 0.3 550 * * * * 550 * * * * 550 * * * * 550 °-0b 1-7 O.Ob 600 °'1 1-3 0.2 600 * * * * 350 67 67 70.5 70 70 70 70.5 70.5 67 67 71 70 71.5 71.5 71 57 57 58 60 60 60 55 '55 55 55 56 51 50 50 52 * Data not yet available b Below detection limit ------- References 1. 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