Carbon is an exogenous compound that usually enters the body via inhalation. Anthracosis is a milder type of pneumoconiosis caused by lung carbon accumulation and is usually asymptomatic. This condition is also known as black lung. Although it occurs mostly in the lungs, it can develop in the spleen, liver, intestinal tract, and lymph nodes.1–3 This condition is more prevalent in city-reared animals such as domestic species. Thus aside from humans, it can also occur in any species living near coal mines especially dogs, horses, and mules.3,4
Air pollution can negatively affect the health of animals and thus may provide biological data for assessing possible risks to the respiratory health of animals. Such data are critical in developing guidelines and policies that shape how air pollution can be controlled. Twenty-one adult feral pigeons (Columbia livia) from urban areas of Seoul and Kwandju in Korea were found to have heavy metal concentrations in liver and bone tissues.5 This research reflected the air quality of urban areas of Korea. However, it failed to reveal any lung histological information on various animals such as zoo, wildlife, and companion animals. Our study includes a diversity of animals (mammalian, avian, and reptilian species) with different habits to give an in-depth look at the possible association of anthracosis with air pollution. With the use of stray dogs as a sentinel model for human exposure, research was done in the industrialized country of Trinidad and Tobago on 56 fresh lungs. Gross and histological data revealed that 51.8% of the dogs had evidence of anthracosis. Furthermore, no association between the presence of anthracosis and any other pathological lesion was identified.6 This study revealed that environmental air pollution may not only affect animals but may also influence human respiratory health. In the Netherlands, a similar study7 was done on wild city pigeons to monitor air pollution as biological indicators; interestingly, high lead and cadmium concentrations in blood, kidney, liver, and lungs were found.
Anthracosis is mostly an incidental finding in the lungs of domestic and wild animals.3 Histopathologically, anthracotic granules are found inside (ladened) and/or outside macrophages, resulting in scattered inflammatory cells. In some cases, such anthracotic granules are associated with edema.8 Histological findings in the lungs of captive common marmosets (Callithrix jacchus) revealed deposition of anthracotic material (dark-brown-to-black pigment) in the perivascular and peribronchiolar area of adult males.9 In dogs, air pollution-associated pulmonary lesions include enlargement of air spaces, nonspecific inflammation, squamous metaplasia, and fibrosis.10,11
Jeonllabuk-do represents the food industry region in South Korea, and it promotes the establishment of research and development infrastructure (food-related) and industrialization. However, the Jeollabuk-do Province is one of the reported provinces to have high levels of particulate matter concentration in South Korea.12 The Jeonju Zoo is situated in Jeollabuk-do and houses tigers, hippos, buffalo, rhinos, camels, and many other exotic birds: it is home to 478 animals made up of 97 different species. With Jeollabuk-do being relatively industrialized, our objective was to study the histological lesions of pulmonary anthracosis in zoo, wildlife, and companion animals over 13 years and how anthracosis cases are associated with the animal’s habitation.
Materials and Methods
Case selection
During a period of 13 years, a total of 350 animals of various species (mammalian, avian, and reptilian) in different parts of Jeollabuk-do Province (South Korea) were examined at postmortem. Animals were eligible for inclusion if they were from the zoo, were companions, and/or were brought from the wild. Farm animals, decomposed carcasses, experimental animals, animals brought in parts (not full carcasses), untraceable animals, and animals outside the area of this study were excluded.
Necropsy and sampling of animals for histopathological examination
Necropsy was done immediately after the animals’ death using a routine protocol. Collected lung tissues were then fixed in 10% neutral buffered formalin and routinely processed for histopathological analysis using a Shandon Citadel 1000 tissue processor.13,14 Thereafter, paraffin sections of about 5 μm in thickness were prepared using a microtome (HM-340E; Thermo Fisher Scientific). These paraffin sections were placed on glass slides with silane coating for Prussian blue staining using an Iron Stain Kit-IRN-1 (ScyTek Laboratories) following the manufacturer’s instructions. Glass slides without silane were stained with hematoxylin and eosin (H&E) according to a standard technique using a MICROM HMS 70 slide stainer. Stained lung paraffin tissue slides were examined by personnel of the Laboratory of Veterinary Pathology, College of Veterinary Medicine using a light microscope (BX-51; Olympus Corp). The degree of anthracosis was evaluated as follows: grade 0, if no anthracotic material was observed; grade 1, if a minimal quantity was noted, just sufficient to reveal its presence; grade 2, if a moderate quantity was observed; and grade 3, if multiple large or many small dust particles had accumulated.11,15
Statistical analysis
For statistical analysis, data were first sorted via Microsoft Excel, and the chi-squared (χ2) test was used to determine whether there was an association between the presence of anthracosis and habitation. Data were analyzed using GraphPad Prism 8.0.1 (244) software (zoo, companion, and wildlife were categorized into those with and without anthracosis). Statistical significance was set at P < .05.
Results
Presence of anthracosis in various species
Representative macroscopic lesions of monkey (rhesus macaques), avian (unknown species), and dog (unknown breed) showed minute (pinpoint size) spots and black pigmentation and in some lesions-coalescing pigmentation. Cross section of Raccoon Dog’s (Nyctereutes procynoides) lung showing visible black spotted pigmentation (Figure 1). Histological analysis of lung tissue of black-crowned night heron (Nycticorax nycticorax), Yorkshire Terrier (Canis lupus familiaris), and lion (Panthera leo) highlighted the presence of carbon particles laden in alveolar macrophages. Additionally, the abundant coarse black pigment in the septal wall bronchiole was observed in the representative images (Figure 2). To compare the presence of dust deposition in lungs (prevalence of anthracosis) according to species, animals were classified into mammalian, avian, and reptilian groups (Table 1). Avian species showed a higher occurrence of anthracosis at 56.7% (38/67) than mammals at 41.9% (116/277). However, there was no carbon deposition in the reptile species observed (0/6). When the presence of lung deposition of dust was estimated, some species of animals such as the lion (Panthera leo) (5/5), badger (Meles leucurus) (5/5), camel (2/2), guanaco (Lama guanicoe) (2/2), llama (2/2), elephant (2/2), chicken (3/3), duck (1/1), and wolf (Canis lupus) (1/1) had anthracosis in all presented cadavers; it should also be noted that the number of animals submitted for necropsy were small. Some kinds of animals (deer [Hydropotes inermis and Capreolus pygargus], kangaroo, mouflon [Ovis musimon], sheep, and reptiles) had no evidence of dust deposited in their lungs in all of their lungs. When the number of species that were less than 10 were excluded, the most animal species showing carbon deposition in lungs were Raccoon Dogs (Nyctereutes procynoides) (8/28), rhesus macaques (14/18), and dogs (50/110).
Photographs showing gross appearance of lung tissue. A—Lung of a monkey (rhesus macaques) showing minute spots that are blackishly discolored, mainly cranial ventrally. B—Avian lung showing dark pigmented areas coalescing (yellow star) and minute black spots (arrow). C—Pinpoint size black pigmentation (black spots) in a scattered fashion throughout the lung surface of a dog (unknown breed). D—Cross section of Raccoon Dog’s (Nyctereutes procynoides) lung showing visible black spotted pigmentation.
Citation: American Journal of Veterinary Research 84, 6; 10.2460/ajvr.23.01.0016
Microphotographs of lung tissue. A—dust-laden macrophages entrapped in the interstitium of a black-crowned night heron (Nycticorax nycticorax). H&E staining scale bar, 20 μm. B—black dust was shown in the alveolar septum of a Yorkshire Terrier (Canis lupus familiaris). H&E staining scale bar, 50 μm. C—Infiltration of black dust in peribronchial of a lion (Panthera leo). H&E scale bar, 100 μm. D—Abundant coarse black pigment filled within alveolar macrophages in the connective tissue of alveolar septa. Iron staining scale bar, 100 μm.
Citation: American Journal of Veterinary Research 84, 6; 10.2460/ajvr.23.01.0016
Cases of anthracosis in mammals, avians, and reptilian species.
| Mammalian species | Avian species | Reptilians species | |||
|---|---|---|---|---|---|
| Mara (Dolichotis patagonum) | 0/1 | Swan (Cynus) | 3/7 | Iguana | 0/1 |
| Finless porpoise (Neophocaena) | 0/1 | Parrot (Psittaciformes) | 2/6 | Crocodile | 0/5 |
| Camel (Camelus) | 2/2 | Owl (Bubo bubo) | 5/9 | ||
| Mouflon (Ovis musimon) | 0/2 | Ostrich (Struthio camelus) | 1/2 | ||
| Leptailurus serval cat | 0/1 | Chicken | 3/3 | ||
| Monkey (rhesus macaques) | 14/18 | Goose | 1/2 | ||
| Siberian tiger | 4/7 | Myna (Gracula religiose) | 1/2 | ||
| Asiatic black bear (Ursus) | 2/4 | Eagle owl | 3/4 | ||
| Dog (various breeds) | 50/110 | Dove (Streptopelia orientalis) | 1/1 | ||
| Cat (various breeds) | 1/7 | Scops owl (Otus scops) | 4/5 | ||
| Leopards (Panthera pardus) | 4/5 | Red-throated diver | 1/2 | ||
| Sea lion (Otariinae) | 0/1 | Silver pheasant | 1/2 | ||
| Tree porcupine (Coendou) | 1/6 | Indian peacock | 1/2 | ||
| Deer (Hydropotes inermis and Capreolus pygargus) | 0/22 | Black-crowned night heron (Nycticorax nycticorax) | 1/3 | ||
| Llama | 2/2 | Mallard | 0/1 | ||
| Wolf (Canis lupus) | 1/1 | Duck | 1/1 | ||
| Eurasian otter (Lutra lutra) | 4/6 | Mandarin duck | 3/5 | ||
| Common buzzard (Buteo buteo) | 2/2 | Numida meleagris | 1/2 | ||
| Lion (Panthera leo) | 5/5 | Lady Amherst’s pheasant | 1/2 | ||
| Raccoon Dog (Nyctereutes procynoides) | 8/28 | Magpie | 2/2 | ||
| Rhinoceros | 0/2 | Egret | 2/4 | ||
| Rabbit | 0/2 | ||||
| Horse | 4/5 | ||||
| Sheep | 0/2 | ||||
| Badger (Meles leucurus) | 5/5 | ||||
| Kangaroo | 0/8 | ||||
| Hippopotamus amphibius | 1/1 | ||||
| Wild boar (Sus scrofa) | 0/1 | ||||
| Ferret (Mustela putorius furo) | 0/1 | ||||
| Muskrat | 0/1 | ||||
| Guanaco (Lama guanicoe) | 2/2 | ||||
| Giraffe | 1/2 | ||||
| Elephant | 2/2 | ||||
| Hippotigris zebra | 1/3 | ||||
| Moose | 0/6 | ||||
| Squirrel (Sciurus vulgaris) | 0/1 | ||||
| Bison | 0/2 | ||||
| 38 species | 116/277 | 21 species | 38/67 | 2 species | 0/6 |
Mammalian, avian, reptilian common name (scientific name).
Regarding the occurrence of anthracosis at various grades in lung tissues, it was 58.1% (161/277) for grade 0 (no particulate material) in mammals. For particulate materials in mammalian species, grade 1 had the highest occurrence (20.9%, 58/277), followed by grade 2 at 13.7% (38/277), and grade 3 at 7.2% (20/277). On the other hand, 43.3% (29/67) of avian species had no particulate material (grade 0; Supplementary Figure S1). For particulate materials in avian lung tissues, grade 1 had the highest occurrence at 25.4% (17/67), followed by grade 2 at 23.9% (16/67) and grade 3 at 7.5% (5/67), which was similar to the occurrence of grade 3 anthracosis in mammalian lung tissues at 7.2% (20/277).
Age and occurrence of anthracosis
Animals were divided into 4 age groups: 1 year or less (n = 38), 1 to 5 years old (42), 5 to 10 years old (42), and over 10 years old (38). Age information was only available for 160 animals among 350. Data revealed that 81% (34/42) of animals in the 5 to 10 age group had deposition of dust in their lungs, whereas the age group of 1 year or younger showed the lowest occurrence of anthracosis particles (47.4%, 18/38; Figure 3). Each age group had a different predominant grade of anthracosis. In the age group of 1 to 5 years, grades 1 and 2 anthracosis showed the highest rate (33.3%, 14/42). However, in the age group of 5 to 10 years, grade 2 anthracosis was the most prevalent (38.1%, 16/42). The proportion of anthracosis with grade 3 was the highest in the age group of 5 to 10 years (14.3%, 6/42). In the age group of over 10 years, grade 3 anthracosis was the most prevalent at 10.5% (4/38). There was no association between the presence of anthracosis and the age groups (P > .05).
The frequency of anthracosis in different age groups. A—Incidence of anthracosis in animals of different age groups: 0 to 1 years (n = 38), 1 to 5 years (42), 5 to 10 years (42), and over 10 years (38). B—Relation between age of animal and grade of anthracosis.
Citation: American Journal of Veterinary Research 84, 6; 10.2460/ajvr.23.01.0016
Frequencies of anthracosis in 3 habitat groups
To investigate the relationship between the frequency of anthracosis and habitat, subjects were divided into 3 groups based on traceable habitation records: zoo (n = 125), wildlife (101), and companion animals (124). Zoo animals had the highest frequency of anthracosis in the lung at 55.2% (69/125), followed by companion animals (45.2%, 56/124) and wildlife animals (28.7%, 29/101; Figure 4). The frequency of grade 1 anthracosis was 26.4% (33/125) in zoo animals, 22.6% (28/124) in companion animals, and 9.9% (10/101) in wildlife animals. Regarding grade 2 anthracosis in lung tissues, it was found in 19.2% (24/125), 11.9% (12/101), and 15.3% (19/124) of zoo, wildlife, and companion animals, respectively.
The frequency of anthracosis in 3 habitats groups. A—Frequencies of anthracosis in zoo animals (n = 125), wildlife animals (101), and companion animals (124). Zoo group: various species of animals submitted by the zoo in Jeonju City; wildlife group: wildlife found in the Jeonbuk Province; companion group: pet animals represented by cats and dogs. B—Relation between environment of animal and grade of anthracosis.
Citation: American Journal of Veterinary Research 84, 6; 10.2460/ajvr.23.01.0016
To establish the possible association between anthracosis frequency and habitat, a χ2 test with 2 rows and 3 columns of a contingency table was used to assess the 2 categorical variables (presence and absence of anthracosis; Supplementary Table S1). The test statistic calculated a P value of .0003, which was less than the cutoff P value of <.05 (GraphPad Prism 8.0.1). Therefore, the null hypothesis H0 was rejected, accepting the alternative hypothesis that there was an association between the presence of anthracosis and the habitat environment.
Discussion
The present study investigated the association between anthracosis cases and the animal’s kept environment. With statistical evidence, we accepted the hypothesis that there was an association between anthracosis and the habitation of the zoo, wildlife, and companion animals (P < .05). This raises a concern, particularly for the zoo animals kept at the Jeonju Zoo situated in the urban area. Anthracosis has also commonly been reported in dogs (stray and in-house) and cats with risk factors for lung cancer mortality.16–18 Therefore, such cases could be contributors to pulmonary-related health risks such as neoplasia in animals. Furthermore, poor air quality can worsen pulmonary diseases in domesticated dogs. Moreover, a study19 on 340 animals (230 dogs and 118 cats) exposed to indoor air pollutants in their homes revealed an association between indoor air pollution (by estimating particulate matter 2.5 concentration) and respiratory disease in these companion animals. In our study, dogs of various breeds revealed a high frequency of anthracosis cases (50/110). However, there was only 1 anthracosis case in domestic cats (1/7) over the study period. Also, in this study, there was a relatively high frequency of anthracosis cases in Raccoon Dogs (Nyctereutes procynoides; 8/28). Most Racoon Dogs have a keen adaptation to periurban and urban habitation in many areas of the world and tend to rapidly colonize new environments; their potential to switch environments makes them susceptible to the effects of urban air quality.20 In a study3 of anthracosis in Dhaka Zoo, 7/27 lung samples of rhesus macaques necropsied showed anthracosis lesions as a public health forecasting for its city dwellers. Therefore, this study not only gives histological findings in the lung of various animal species but also strongly suggests that the air pollution in Jeonllabuk-do may be a predisposing factor to this condition (pulmonary anthracosis).
This study is the first to demonstrate anthracosis lesions in mammalian, avian, and reptilian species in South Korea. Avian species showed a higher frequency of anthracosis at 56.7% (38/67) than mammals at 41.9% (116/277). Exotic birds from the zoo were kept in open enclosures. Because of the constant exposure to the polluted city air, they were more susceptible to black lung than the birds presented from the wild. Six reptiles (iguanas and crocodiles) brought from the zoo showed no cases of anthracosis. Further investigation revealed that the environment used to house these poikilotherm species was closed and/or temperature controlled unlike the mammals and avian species habitation. This raises a concern about the consequence of exposure to smoke and dust on the animals living in open enclosures.
Studies21–23 have reported that exposure to dust is closely related to pulmonary problems, including inflammation, pulmonary neoplasia, and fibrosis of the lungs. The limitations of this study were that grades of anthracosis did not exhibit distinct correlations with pulmonary inflammation. Although infiltration of inflammatory cells around deposited dust materials was found in some cases, the possibility of other respiratory infections could not be ruled out. Thus, the association between anthracosis and pulmonary problems was not reported in this study. Also, there was no association between the presence of anthracosis and the age groups (P > .05). However, the frequency of anthracosis was highest in the age group 5 to 10 years and over 10 years. Several factors may have contributed to the high frequencies in older animals, such as continuous exposure to air pollutants, the amount of air pollution in the environment, and animals’ immunity.1 Therefore, it was difficult to conclude the relationship between the age of an animal and the presence of anthracosis in this particular study.
The significant association of anthracosis found with reference to gross and histopathological findings and the air quality in Jeollabuk-do Province strongly suggests that air pollutants may pose a health risk to both animals and humans. Special attention must be paid to minimizing dust and smoke in the province, thereby reducing risks of anthracosis in zoo, wildlife, and companion animals. Research on the constant measurement of air pollutants (particulate matter) in the province must be supported.
Supplementary Materials
Supplementary materials are posted online at the journal website: avmajournals.avma.org.
Acknowledgments
This research was supported by Basic Science Research Program through the National Research Foundation (NRF) funded by the Ministry of Education (2019R1A6A1A03033084). In addition, this subject is supported by the National Institute of Wildlife Disease Control and Prevention as “Specialized Graduate School Support Project for Wildlife Disease Specialists.”
The authors have nothing to declare.
References
- 1.↑
Mirsadraee M. Anthracosis of the lungs: etiology, clinical manifestations and diagnosis: a review. Tanaffos. 2014;13(4):1–13.
- 2.
Seaton A. Coal and the lung. Thorax. 1983;38(4):241–243. doi:10.1136/thx.38.4.241
- 3.↑
Ahasan SA, Chowdhury EH, Azam SU, Parvin R, Rahaman AZ, Bhuyan AR. Pulmonary anthracosis in Dhaka Zoo collections–a public health forecasting for city dwellers. J Threat Taxa. 2010;2(11):1303–1308. doi:10.11609/jott.o2334.1303-8
- 4.↑
Zachary JF, McGavin DM. Pathologic Basis of Veterinary Disease. 4th ed. Mosby Elsevier; 2007:49–50.
- 5.↑
Nam DH, Lee DP, Koo TH. Monitoring for lead pollution using feathers of feral pigeons (Columba Livia) from Korea. Environ Monit Assess. 2004;95(1–3):13–22. doi:10.1023/B:EMAS.0000029898.28393.30
- 6.↑
Mohamed RA, Georges K, Rajh S, Suepaul RB. A pilot study on the lung morphology of shelter dogs in relation to air pollution in Trinidad. Am J Vet Res. 2022;83(10):1–6. doi:10.2460/ajvr.22.05.0077
- 7.↑
Schilderman PAEL, Hoogewerff JA, van Schooten FJ, et al. Possible relevance of pigeons as an indicator species for monitoring air pollution. Environ Health Perspect. 1997;105(3):322–330. doi:10.1289/ehp.97105322
- 8.↑
Naccache JM, Monnet I, Nunes H, et al. Anthracofibrosis attributed to mixed mineral dust exposure: report of three cases. Thorax. 2008;63(7):655–657. doi:10.1136/thx.2006.070243
- 9.↑
Bleyer M, Kunze M, Gruber-Dujardin E, Mätz-Rensing K. Spontaneous lung pathology in a captive common marmoset colony (Callithrix jacchus). Primate Biol. 2017;4(1):17–25. doi: 10.5194/pb-4-17-2017.
- 10.↑
Calderón-Garcidueñas L, Mora-Tiscareño A, Fordham LA, et al. Canines as sentinel species for assessing chronic exposures to air pollutants: part 1. Respiratory pathology. Toxicol Sci. 2001;61(2):342–355. doi:10.1093/toxsci/61.2.342
- 11.↑
Heyder J, Takenaka S. Long-term canine exposure studies with ambient air pollutants. Eur Respir J. 1996;9(3):571–584. doi:10.1183/09031936.96.09030571
- 12.↑
Cho B, Song M. Distributions and origins of PM10 in Jeollabuk-do from 2010 to 2015. J Korean Soc Atmospher Environ. 2017;33(3):251–264. doi:10.5572/kosae.2017.33.3.251
- 13.↑
Kato A, Kagawa J. Morphological effects in rat lungs exposed to urban roadside air. Inhal Toxicol. 2003;15(8):799–818. doi:10.1080/08958370390217855
- 14.↑
Leya M, Kim WK, Cho JS, et al. Vaccination of goats with a combination Salmonella vector expressing four Brucella antigens (BLS, PrpA, Omp19, and SOD) confers protection against Brucella abortus infection. J Vet Sci. 2018;19(5):643–652. doi:10.4142/JVS.2018.19.5.643
- 15.↑
Schoning P, Abraham JL, Burnett BR. Silicate and metal dust in lungs of Greyhounds. Am J Vet Res. 1996;57(7):1006–1009.
- 16.↑
Bettini G, Morini M, Marconato L, Marcato PS, Zini E. Association between environmental dust exposure and lung cancer in dogs. Vet J. 2010;186(3):364–369. doi:10.1016/j.tvjl.2009.09.004
- 17.
Subramanian J, Govindan R. Lung cancer in never smokers: a review. J Clin Oncol. 2007;25(5):561–570. doi:10.1200/JCO.2006.06.8015
- 18.↑
Beelen R, Hoek G, van den Brandt PA, et al. Long-term exposure to traffic-related air pollution and lung cancer risk. Epidemiology. 2008;19(5):702–710. doi:10.1097/EDE.0b013e318181b3ca
- 19.↑
Lin CH, Lo PY, Wu HD, Chang C, Wang LC. Association between indoor air pollution and respiratory disease in companion dogs and cats. J Vet Intern Med. 2018;32(3):1259–1267. doi:10.1111/jvim.15143
- 20.↑
Myśliwy I, Perec-Matysiak A, Hildebrand J. Invasive raccoon (Procyon lotor) and raccoon dog (Nyctereutes procyonoides) as potential reservoirs of tick-borne pathogens: data review from native and introduced areas. Parasit Vectors. 2022;15(1):1–12. doi:10.1186/s13071-022-05245-3
- 21.↑
Kim YJ, Jung CY, Shin HW, Lee BK. Biomass smoke induced bronchial anthracofibrosis: presenting features and clinical course. Respir Med. 2009;103(5):757–765. doi:10.1016/j.rmed.2008.11.011
- 22.
Herlihy JP, Vermeulen MW, Joseph PM, Hales CA. Impaired alveolar macrophage function in smoke inhalation injury. J Cell Physiol. 1995;163(1):1–8. doi:10.1002/jcp.1041630102
- 23.↑
Takaki Y. Histological effects of long-term inhalation studies of exhaust from the diesel engine on F-344 rats. Haigan. 1991;31(1):56–61. doi:10.2482/haigan.31.25
