2022 Volume 4 Issue 1 Article ID: 2022-0002-OA
Objectives: In this study, we applied novel nasal filters to assess animal allergen exposure of veterinary staff during their normal daily routine. Methods: Rhinix nasal filters were worn during work by 94 employees at different veterinary practices and 18 employees at a research institute, who acted as controls representing an animal-free environment. Contact with animals and the activities performed were documented by the study participants using a short questionnaire. Major allergens of cats (Fel d 1), dogs (Can f 1), and domestic mites (DM) were measured using fluorescence enzyme immunoassays. Results: At the practices, Can f 1 was detected in 98%, Fel d 1 in 82%, and DM allergens in 39% of the samples. Allergens were also detected in some control samples (6% for Can f 1, 39% for Fel d 1, and 17% for DM) but in very low concentrations. There was a highly significant difference between allergen levels in veterinary workers who treated at least one cat or dog during the sampling period and those who did not (2.66 vs. 0.70 ng/filter for Can f 1 and 1.01 vs. 0.20 ng/filter for Fel d 1). The amount of sampled Fel d 1 increased significantly with increasing duration of contact with cats. This effect was not observed for Can f 1. Conclusions: The majority of veterinary workers are exposed to dog and cat allergens, even without direct contact with these animals. Rhinix nasal filters may be considered a simple and easily applicable method for monitoring personal allergen exposure.
There is great interest in the environmental sampling of indoor allergens in order to assess exposure. Since inhalation of allergens is the most relevant exposure route, allergen exposure assessment should ideally be based on the measurement of airborne allergen concentrations1). Two main approaches are used to quantify indoor allergens: area sampling (the sampler is located in a specific room) and personal sampling (the sampler is carried by the individual). The collection of airborne dust on filters that are mounted within the breathing zone of subjects carrying portable pumps is regarded as the gold standard in occupational settings2). This method is well-standardized and enables the collection of particles of defined sizes, but it is also expensive, time- and labor-intensive, noisy, cumbersome, and carries a high risk of technical difficulties. Another option that facilitates the collection of personal samples is the use of nasal air samplers or nasal filters worn in the nostrils and powered by the wearer’s own inhalation. Indeed, several studies have been published in which the nasal air sampling method was used to detect inhaled cat3), mite4), and cockroach allergens5) in domestic environments, as well as latex6), flour7), and rodent allergens8) in occupational settings. The sampling devices used in these studies collected inhaled particles by impaction onto adhesive tapes or into inner cores containing liquid adhesive. A disadvantage is that after each sampling, the equipment must be cleaned and disinfected prior to the next measurement and/or user.
In 2014, Kenney et al. described new nasal filters (Rhinix, Aarhus, Denmark) that were developed with the primary aim to prevent symptoms of allergic rhinitis during pollen season9). These filters consist of a low-air-resistance filtering membrane covered in a flexible butterfly-shaped copolymer frame, and is designed for single use (Figure 1). The filtering membrane is made of polypropylene non-woven fibers and removes particles by means of interception and impaction. The Rhinix nasal filters were found to significantly reduce nasal symptoms (sneezing, itching, and runny nose) compared with the placebo (filters without membrane)10) and were convenient and comfortable to use11). The applicability of Rhinix nasal filters for allergen exposure monitoring was proven using bench-top testing with a house dust nebulizer in a closed system. This experiment showed that the major allergens from dust mite, cat, dog, and pollen are captured by the nasal filter once present in the dust12). Furthermore, the Rhinix nasal filters were successfully used to investigate equine allergen levels released into the air during grooming13). However, in this study they were applied under extreme high-exposure conditions, during the same activity, and for the same amount of time (10 min). The aim of the present study was to characterize exposure levels to cat (Fel d 1), dog (Can f 1), and domestic mite (DM) allergens in veterinary personnel using Rhinix nasal filters during daily work routines.
Rhinix nasal filter
This study was part of the project “AllergoMed” which was approved by the Ethics Committee of the Ruhr University Bochum in Germany (registration number: 17-6022) on July 4, 2017. All study participants gave written informed consent and received financial compensation for their participation. Anonymity and confidentiality were assured.
Nasal air samplingThe study was conducted in three mixed-animal and thirty-two small animal veterinary practices from October 2017 until February 2019. Participation in the project was voluntary. Nasal air sampling was supervised by a professional field worker, who instructed the volunteers in the use of the sampling equipment. Veterinary practices’ employees were provided with nasal filters size L (Rhinix) and requested to wear them during their daily work routine. Collection time was between 60 and 240 min (median 90 min). Before insertion, subjects were instructed to blow their noses. A mirror was used to check that the device was positioned correctly in the nose. When inserting and removing the nasal filters, a fresh pair of gloves were used to grip the center of the bridge to avoid contaminating the membranes. Subjects filled out a short questionnaire addressing the type and duration of their activities, the type of the room in which the activity was performed, as well as the species and number of animals treated. Due to the large number of different tasks performed during work, all reported activities were classified according to direct contact with animals (necessary touching of the animals: yes/no) and not just the presence of animals in the room (Table 1). All activities with direct contact with cats or dogs were grouped together and analyzed in three different ways:
| Activities with direct contact to cats/dogs | Activities without direct contact to cats/dogs |
|---|---|
| examination of cats or dogs | examination of other species (e.g. rabbit, guinea pig, birds) |
| radiology/ultrasonography | consultations |
| blood sampling | working at the reception |
| surgery | laboratory work |
| surgery preparation/assistance | office/administration work |
| hair trimming and shaving | replenishment of supplies |
| anesthesia | working in the utility room |
| euthanasia | errands |
| physiotherapy | cleaning the practice rooms |
| dental treatment | |
| working in the inpatient ward |
1) number of cats or dogs handled during the total sampling time;
2) contact with cats or dogs in minutes (the duration of each activity in minutes was summed and the sum was set equal to 100%); and
3) contact with cats or dogs in percent (the sum of contact minutes was related to the total sampling time (100%) and expressed as a percentage).
As a control for the veterinary practices, nasal air sampling was carried out in a completely animal-free environment. Employees at a research institute wore the nasal filters for 60 min during laboratory or office work.
ExtractionAfter sampling, the nasal sampler was put directly into 5 mL-extraction tubes and sent to the laboratory using regular mail. The samples were stored at 4°C until extraction (4–7 days), at which time the bridge between the two membranes was cut and allergens were extracted by gentle shaking of the membranes in 1.5 mL phosphate buffered saline with 0.05% Tween 20 (PBST) for 1 hour at room temperature. The membranes were removed with clean tweezers, and the extracts were centrifuged for 15 min at 3,000 x g. The supernatants were aliquoted and stored at −80°C until analysis.
Allergen quantificationMajor allergens from cat (Fel d 1) and dog (Can f 1) were quantified using monoclonal antibodies and calibration standards purchased from Indoor Biotechnologies Inc. (Charlottesville, VA, USA) according to protocols described previously14). A sensitive immunoassay based on polyclonal antibodies to Dermatophagoides farinae extract was used to estimate domestic mite allergen levels. Due to strong cross-reactivity, this assay detects allergens from several house dust and storage mite species15). Values below the lower limit of detection (LOD) were replaced by 2/3 LOD. The LODs were 0.015 ng/filter for Fel d 1 and Can f 1 and 0.05 ng/filter for domestic mites.
Statistical analysisThe descriptive statistics, Pearson correlation of log-transformed values and statistical analysis using non-parametric Mann-Whitney test or Kruskal-Wallis test (corrected for multiple comparisons using Dunn’s test) were made with GraphPad Prism version 9 (GraphPad Software, Inc., La Jolla, CA, USA). P-values <0.05 were considered statistically significant.
In total, 94 samples from veterinary practices and 18 samples from a research institute (controls) were collected and analyzed. Ninety-eight percent of samples collected at the practices contained Can f 1, 82% Fel d 1, and 39% domestic mite allergens. Conversely, Can f 1 was detected in only one (6%), Fel d 1 in seven (39%), and domestic mite allergen in three (17%) of the control samples. Can f 1 and Fel d 1 levels were significantly higher in samples from veterinary practices than in the control samples (Figure 2A and Figure 2B). No significant difference was found between veterinary practices and the research institute with respect to domestic mite allergen levels (Figure 2C). At the practices, the levels of inhaled animal allergens differed by more than 1,000-fold, ranging from <0.015 to 34.32 ng/filter for Can f 1 and <0.015 to 23.01 ng/filter for Fel d 1. The levels of domestic mite allergens were very low compared to those of the animal allergens (<0.05 to 1.81 ng/filter). The median Can f 1 concentration (1.91 ng/filter) was approximately four times higher than the Fel d 1 median value (0.47 ng/filter) (Figure 2). Can f 1 and Fel d 1 results showed a very weak but significant correlation to each other (r=0.224, p=0.0297). Can f 1 and Fel d 1 levels were significantly higher in staff who treated at least one cat or dog during the sampling period compared to those who had no contact to these animals (Figure 3).
Levels of dog (A), cat (B), and domestic mite allergen (C) in nasal filter samples collected from employees of veterinary practices and research institute. Vertical bars show the minimum and maximum values, and numbers within the boxes represent the median values. Significant differences between group ranks are indicated by p-values. The LODs are marked with a dotted line.
Levels of cat allergen (A) and dog allergen (B) in nasal filter samples collected from veterinary practice employees in relation to contact with animals. Vertical bars show the minimum and maximum values, and numbers within the boxes represent the median values. Significant differences are indicated by p-values.
To investigate if the allergen levels are associated with increasing exposure, samples from individuals with direct animal contact were divided into groups according to the number of animals treated during the sampling period, as well as the duration of contact with the animals in minutes or in percentage of the total sampling time. The concentration of sampled Fel d 1 increased significantly only with increasing contact duration (Figure 4C). In contrast, no significant differences were seen for Can f 1 levels, regardless of animal number or duration of contact with dogs (Figure 5).
Cat allergen (Fel d 1) concentrations in nasal filter samples depending on the exposure intensity: (A) number of cats treated, (B) contact with cats in minutes, (C) contact with cats in percent of total sampling time. Vertical bars show the minimum and maximum values and numbers within the boxes represent the median values.
Dog allergen (Can f 1) concentrations in nasal filter samples depending on the exposure intensity: (A) number of dogs treated, (B) contact with dogs in minutes, (C) contact with dogs in percent of total sampling time. Vertical bars show the minimum and maximum values and numbers within the boxes represent the median values.
Dog and cat allergens were detected in the majority of samples collected from subjects working in veterinary practices, even if there was no direct contact with dogs (25 of 26, 96%) or cats (33 of 43, 77%). These findings were not unexpected because according to our previous published study, animal allergens are detectable in all areas of veterinary practices, including rooms that are never directly occupied by the animals, such as laboratories, offices and break rooms16). Once the employees came into direct contact with at least one cat or dog, the allergen levels in the nasal filter samples increased by five times for Fel d 1 and by 3.5 times for Can f 1. Hence, the method efficiently captures exposure peaks, which is critical as these peak exposures are considered to be the most important factors for sensitization and symptom expression17). Moreover, sampling using Rhinix nasal filters seems to be a very sensitive method, because animal allergens were even detected in some control samples collected from employees at a research institute that is completely free of animals but not of animal owners. The only Can f 1-positive sample collected in the control group belonged to a dog owner and six of the seven Fel d 1-positive samples came from cat owners. The origin of allergens detected is most likely a result of pet-contaminated clothing and hair, which were found to be important sources of allergen exposure18,19). O’Meara et al. found also that personal exposure to cat allergens at work was massively increased if the test person wore an item of clothing belonging to a cat owner3). In contrast to animal allergens, domestic mite allergens were detected very rarely and in much lower concentrations. This is probably due to the fact that both areas (veterinary practices and research institute) are cleaned frequently and do not contain upholstered furniture, beds, or carpets, which are the most important reservoir for mite allergens20).
Although clear differences in allergen exposure were found between animal-free area and veterinary practices, and between employees with and without direct contact to animals, the nasal sampling method failed to detect an increase in exposure depending on the number of animals treated or the duration of treatment. For the cat allergen, a trend of increased exposure was observed, but the differences were mostly not significant. For the dog allergen, exposure did not differ depending on the number of dogs treated or the duration of contact with dogs. We excluded saturation of the nasal filter membrane due to its binding capacity as a potential explanation, since much higher values were obtained in a study on horse allergens (up to 47,500 ng/filter for Equ c 1 and 4,080 ng/filter for Equ c 413). In the present study, the highest values were approximately 25 ng/filter for Fel d 1 and 38 ng/filter for Can f 1. Thus, the question arises whether an increase in exposure with the number of animals treated or the duration of treatment would be expected at all, especially since the study was conducted under natural conditions and not under a controlled experimental environment. Exposure to most aeroallergens fluctuates massively with time, ventilation, and activity in the sampling room. We found striking variations in allergen levels within each category for all characteristics assessed. These variations may be influenced by several factors, including work-related variations (breathing differences, [mis]fit of nasal filters, and handling of nasal filters) and task-related variations (tasks are performed differently between practices and within a practice by workers). For example, it is known that working with physically-active animals (e.g. behavioral studies) results in higher exposure than with anesthetized animals21), suggesting that surgery over a longer period of time may lead to a lower exposure than a short examination of an active animal. In addition, allergen loads shed by an individual animal can vary enormously. Variations in allergen content of hair up to four orders of magnitude were observed in dogs22), horses13,23), and cattle24) of different breeds and sexes. Another factor that could influence the high variability of allergen levels was talking during dust collection, which was not restricted as in other studies8). Indeed, talking prevents nasal breathing, but banning communication could complicate the workflow, and would not reflect the real day-to-day interactions among the staff, especially since our aim was to disrupt the workflow as little as possible.
One limitation of our study is that we did not perform the exposure measurements using the gold standard method (active airborne dust sampling using person carried pumps). However, this method is unsuitable for veterinary practices because the noise of the pumps can increase nervousness among the animals, thus elevating the risk of injury to the staff. Animal bites and scratches are the most common occupational hazards for veterinarians25). However, previous studies have shown that personal air sampling correlates well with nasal sampling using Rhinix nasal filters26) or other devices6,7,8). Nevertheless, we can compare the results of the nasal sampling performed here with those from our previous study on cat, dog, and mite allergens in veterinary practices using electrostatic cloths for dust sampling (long-term measurement over 14 days)16). The highest levels were found for Can f 1 (793 ng/m2), followed by Fel d 1 (440 ng/m2), and the lowest levels were found for domestic mite allergens (60 ng/m2). Although the factors between allergen concentrations are not equal, the same order was found when measured with Rhinix nasal filters (1.91 ng/filter for Can f 1, 0.47 ng/filter for Fel d 1, and below LOD for domestic mite). A possible explanation for higher Can f 1 values compared to Fel d 1 values is that dogs can release more allergens due to their larger average size and body surface area.
ConclusionRhinix nasal filters represent a simple and inexpensive device for monitoring personal allergen exposure. This dust sampling equipment also seems to be especially suited for measurements in noise-sensitive work areas, and the method is very sensitive, as cat and dog allergens were detected in animal-free areas where pet owners work. It was also possible to distinguish between areas of high and low exposure. Therefore, occupational hygienists should consider nasal filters as a useful tool to identify, assess, and control health hazards at the workplace.
The authors thank the employees of the veterinary practices for their support and participation in our study. We acknowledge Christina Czibor for the laboratory analyses and Dr. Rosemarie Marchan for checking and improving the language of the manuscript.
MR, AN and IS contributed to the study conception, supervising data collection and data interpretation. EZ, OK, AB, and FH contributed to the acquisition, analysis and interpretation of the data. EZ wrote the first draft of the manuscript. All authors critically reviewed the manuscript and agreed with the final version.
This study was financially supported by the Deutsche Gesetzliche Unfallversicherung and Berufsgenossenschaft für Gesundheitsdienst und Wohlfahrtspflege (IPA-148-AllergoMed).
None declared.
