Assessment of respiratory and systemic toxicity of Benzalkonium chloride following a 14-day inhalation study in rats.

BACKGROUND: Although biocides at low concentrations have been used to control pests, they can be more harmful than industrial chemicals as humans are directly and frequently exposed to such biocides. Benzalkonium chloride (BAC or BKC) is a non-toxic substance used to control pests. Recently, BAC has been increasingly used as a component in humidifier disinfectants in Korea, raising a serious health concern. Moreover, it poses significant health hazards to workers handling the chemical because of direct exposure. In the present study, we aimed to evaluate the respiratory toxicity of BAC due to its inhalation at exposure concentrations of 0.8 (T1 group), 4 (T2 group) and 20 (T3 group) mg/m3. RESULTS: In our previous study on the acute inhalational toxicity of BAC, bleeding from the nasal cavity was observed in all the rats after exposure to 50 mg/m3 BAC. Therefore, in this study, 20 mg/m3 was set as the highest exposure concentration, followed by 4 and 0.8 mg/m3 as the medium and low concentrations for 6 h/day and 14 days, respectively. After exposure, recovery periods of 2 and 4 weeks were provided. Additionally, alveolar lavage fluid was analyzed in males of the BAC-exposed groups at the end of exposure and 2 weeks after exposure to evaluate oxidative damage. In the T3 group exposed to BAC, deep breathing, hoarseness, and nasal discharge were observed along with a decline in feed intake and body weight, and nasal discharge was also observed in the T1 and T2 groups. ROS/RNS, IL-1ß, IL-6, and MIP-2 levels decreased in a concentration-dependent manner in the bronchoalveolar lavage fluid. Histopathological examination showed cellular changes in the nasal cavity and the lungs of the TI, T2, and T3 groups. CONCLUSIONS: As a result, it was confirmed that the target organs in the respiratory system were the nasal cavity and the lungs. The adverse effects were evaluated as reversible responses to oxidative damage. Furthermore, the no observed adverse effect level was found to be less than 0.8 mg/m3 and the lowest benchmark dose was 0.0031 mg/m3. Accordingly, the derived no-effect level of BAC was calculated as 0.000062 mg/m3.

Immunohistochemical characterization of oxidative stress in the lungs of rats exposed to the humidifier disinfectant polyhexamethylene guanidine hydrochloride.

Polyhexamethylene guanidine hydrochloride (PHMG-HCl), an antimicrobial additive in humidifier disinfectants, was associated with the pulmonary disease outbreak in South Korea. However, PHMG-mediated oxidative stress has only been studied in vitro. Here, we evaluated PHMG-induced oxidative stress in the lungs of rats exposed to PHMG-HCl. Male F344 rats were exposed to different concentrations of PHMG-HCl for 13-weeks via whole-body inhalation. Histopathological examination of the exposed rats showed the presence of lung lesions, including alveolar/interstitial fibrosis with inflammatory cell infiltration, bronchioalveolar hyperplasia, bronchiolar/alveolar squamous metaplasia, bronchial/bronchiolar epithelial detachment, and alveolar hemorrhage. Immunohistochemical analysis showed that 4-hydroxynonenal (4-HNE) was expressed in the bronchiolar epithelium, mainly in Clara cells and macrophages of the fibrotic tissue. The number of 4-HNE-positive cells increased significantly in a dose-dependent manner. This is the first in vivo study to report PHMG-induced oxidative stress. Our study provides clues to elucidate the mechanisms underlying PHMG-induced damage in patients affected by humidifier disinfectants.

The effects of 4-week inhalation exposure to titanium nitride on lungs of Sprague-Dawley rats.

Titanium nitride (TiN) is a ceramic material with physical properties such as extreme hardness, high decomposition temperature, defect structure, and gold-yellow color. TiN is generally considered non-toxic and safe; however, hazards have not been identified, especially in workers after inhalation exposure. Here, we conducted a four-week inhalation toxicity study of TiN using a nose-only inhalation exposure system in Sprague-Dawley rats. Rats were exposed to TiN for 4 weeks (6 h a day, 5 days per week) at target concentrations of 45, 90, and 180 mg/m3. Clinical signs, mean body weight changes, hematology, blood biochemistry, necropsy, organ weight, bronchoalveolar lavage fluid analysis, and histopathological findings were observed. Analytical concentrations of the low, middle, and high-concentration groups were 45.55 ± 3.18 mg/m3, 90.69 ± 7.30 mg/m3, and 183.87 ± 15.21 mg/m3, respectively. The mass median aerodynamic diameter (MMAD) for the low, middle, and high-concentration groups were 1.44 ± 0.07 µm, 1.47 ± 0.18 µm, and 1.68 ± 0.16 µm, and the geometric standard deviation (GSD) was 2.24 ± 0.03, 2.31 ± 0.16, and 2.43 ± 0.11, respectively. No systemic adverse effects were observed after inhalation exposure to TiN; however, histopathological findings (increased phagocytic macrophages and alveolar/bronchiolar epithelial hyperplasia) and Bronchoalveolar Lavage Fluid (BALF) analysis (elevated lactate dehydrogenase and gamma-glutamyltransferase values) showed adverse effects on the lungs in the middle and high-concentration groups. Based on these results, the no observed adverse effect concentration (NOAEC) is suggested to be 45 mg/m3.

N-methylformamide induces multiple organ toxicity in Fischer 344 rats.

N-Methylformamide (NMF) is a widely used chemical (CAS No.: 123-39-7) in several industries and its usage is continuously increasing. However, studies for NMF have been focused on hepatotoxicity from now. Its toxicity profile has not yet been established owing to limited toxicity data. Therefore, we evaluated systemic toxicity via NMF inhalation. We exposed 0, 30, 100, and 300 ppm NMF to Fischer 344 rats for 6 h/day, 5 days a week for 2 weeks. Clinical signs, body weights, food consumption, hematologic parameters, serum chemistry measurements, organ weights, necropsy, and histopathology were performed. Two females exposed to 300 ppm NMF died during exposure period. Decrease of food consumption and body weight in both sexes exposed to 300 ppm in females exposed to 100 ppm were noted during exposure period. Increased RBC and HGB were noted in females exposed to 300 ppm. A decrease in the levels of ALP and K and increase in the levels of TCHO and Na were observed in both sexes exposed to 300 and 100 ppm. Increased levels of ALT, AST, BUN and decreased levels of TP, ALB, Ca were observed in females exposed to 300 and 100 ppm. The relative liver weight was elevated in both sexes exposed to 300 and 100 ppm NMF. Hypertrophy in the liver and submandibular glands and nasal cavity injuries were noted in both sexes exposed to 300 and 100 ppm NMF. Tubular basophilia of the kidneys were noted in females exposed to 300 ppm NMF. We revealed that NMF affect several organs including the kidneys not only the liver and NMF-related toxicity is predominant in female rats. These results could contribute to the development of NMF toxicity profile and may help in developing strategies for the control of occupational environmental hazards related to NMF.

Evaluation of subchronic repeated administration toxicity of ammonium nitrate in rats.

Ammonium nitrate is a chemical mostly used in agriculture and munitions to produce fertilizers and explosives, respectively. Its annual production and consumption exceed ten million tons. Despite is diverse uses, large production and consumption, and occupational risk, information on the toxicity that results from oral exposure to ammonium nitrate is limited. In this study, the safety of ammonium nitrate was therefore evaluated by observing its subchronic toxicity in rats. Ammonium nitrate (0, 100, 300 and 1000 mg/kg/day) was orally administered by gavage to rats at 5 times/week for 13 weeks. Reversibility of the effects of 1000 mg/kg/day was assessed in rats after 2 weeks. Mortality, clinical signs, body weight, and food consumption were monitored. Hematology, serum chemistry, urinalysis, organ weight, necropsy, and histopathology were performed. Salivation was intermittently observed in both sexes receiving 300 and 1000 mg/kg/day ammonium nitrate, which normalized 2 weeks post-treatment. Urine volume increased in both sexes receiving 1000 mg/kg/day ammonium nitrate. Urine pH decreased in both sexes of all dosing groups when compared with the concurrent control group. Urinary changes normalized 2 weeks post-treatment. Blood urea nitrogen levels increased in males receiving 1000 mg/kg/day, but normalized 2 weeks later. Potassium level in males and sodium and chloride levels in both sexes receiving 1000 mg/kg/day ammonium nitrate decreased, but normalized 2 weeks later. Hypertrophy of zona glomerulosa in the adrenals was observed in both sexes receiving 1000 mg/kg/day and in females receiving 300 mg/kg/day ammonium nitrate. After a 2-week recovery period, the same lesion was observed in one female receiving 1000 mg/kg/day ammonium nitrate. Our results indicate that ammonium nitrate induces reversible salivation, increases BUN levels, induces acidic diuresis with decreases in sodium, potassium, and chloride levels, and induces ZG hypertrophy. These results shed light on the toxicity profile of ammonium nitrate.