Inhalation of chlorine gas

N-acetyl cysteine mitigates lung damage and inflammation after chlorine exposure in vivo and ex vivo

The objective of this study was to explore the effects of antioxidant treatments, specifically N-acetylcysteine (NAC) and N-acetylcysteine amide (NACA), in a mouse model of chlorine (Cl2)-induced lung injury. Additionally, the study aimed to investigate the utility of pig precision-cut lung slices (PCLS) as an ex vivo alternative for studying the short-term effects of Cl2 exposure and evaluating antioxidant treatments. The toxicological responses were analyzed in Cl2-exposed mice (inflammation, airway hyperresponsiveness (AHR)) and PCLS (viability, cytotoxicity, inflammatory mediators). Airways contractions were assessed using a small ventilator for mice and electric-field stimulation (EFS) for PCLS. Antioxidant treatments were administered to evaluate their effects. In Cl2-exposed mice, NAC treatment did not alleviate AHR, but it did reduce the number of neutrophils in bronchoalveolar lavage fluid and inflammatory mediators in lung tissue. In PCLS, exposure to Cl2 resulted in concentration-dependent toxicity, impairing the lung tissue's ability to respond to EFS-stimulation. NAC treatment increased viability, mitigated the toxic responses caused by Cl2 exposure, and maintained contractility comparable to unexposed controls. Interestingly, NACA did not provide any additional treatment effect beyond NAC in both models. In conclusion, the establishment of a pig model for Cl2-induced lung damage supports further investigation of NAC as a potential treatment. However, the lack of protective effects on AHR after NAC treatment in mice suggests that NAC alone may not be sufficient as a complete treatment for Cl2 injuries. Optimization of existing medications with a polypharmacy approach may be more successful in addressing the complex sequelae of Cl2-induced lung injury.

N-acetyl cysteine protects against chlorine-induced tissue damage in an ex vivo model

High-level concentrations of chlorine (Cl₂) can cause life-threatening lung injuries and the objective in this study was to understand the pathogenesis of short-term sequelae of Cl₂-induced lung injury and to evaluate whether pre-treatment with the antioxidant N-acetyl cysteine (NAC) could counteract these injuries using Cl₂-exposed precision-cut lung slices (PCLS). The lungs of Sprague-Dawley rats were filled with agarose solution and cut into 250 μm-thick slices that were exposed to Cl₂ (20-600 ppm) and incubated for 30 min. The tissue slices were pre-treated with NAC (5-25 mM) before exposure to Cl₂. Toxicological responses were analyzed after 5 h by measurement of LDH, WST-1 and inflammatory mediators (IL-1β, IL-6 and CINC-1) in medium or lung tissue homogenate. Exposure to Cl₂ induced a concentration-dependent cytotoxicity (LDH/WST-1) and IL-1β release in medium. Similar cytokine response was detected in tissue homogenate. Contraction of larger airways was measured using electric-field-stimulation method, 200 ppm and control slices had similar contraction level (39 ± 5%) but in the 400 ppm Cl₂ group, the evoked contraction was smaller (7 ± 3%) possibly due to tissue damage. NAC-treatment improved cell viability and reduced tissue damage and the contraction was similar to control levels (50 ± 11%) in the NAC treated Cl₂-exposed slices. In conclusion, Cl₂ induced a concentration-dependent lung tissue damage that was effectively prevented with pre-treatment with NAC. There is a great need to improve the medical treatment of acute lung injury and this PCLS method offers a way to identify and to test new concepts of treatment of Cl₂-induced lung injuries.

Chlorine exposure during a biological decontamination study in a mock subway tunnel

The Underground Transport Restoration (UTR) Operational Technology Demonstration (OTD) was a full-scale field study focused on remediation of a subway system after contamination with a Bacillus anthracis (Ba) surrogate (Bacillus atrophaeus, subspecies globigii [Bg]). The study involved all aspects of subway system remediation following contamination with a biological surrogate, including characterization, clearance sampling, and waste management.^{[ 1 ]} Personal exposure to chlorine gas was also monitored throughout the decontamination portion of the study. Process-based personal monitoring for chlorine was conducted using portable single gas monitors with chlorine sensors during Level A entry into the biologically-contaminated area (exclusion zone) during spraying operations. Additional monitoring was conducted during the mixing of pH-adjusted bleach solutions and waste item decontamination (immersion dunking). An analysis of variance was performed to compare process-based time-averaged chlorine exposure among the similar exposure groups. Chlorine exposure was highest for the Decon Sprayers, which was expected based on their proximity to the spray streams. Peak exposure levels (5-sec readings) ranged from 11 to at least 50 parts per million (ppm). It is likely that exposure exceeded 50 ppm, but this was the upper limit of measurement. Oversight personnel were farther away from the spray operation but still had significant peak chlorine exposures of 13-26 ppm. The rail cart operators had peak exposures of 13-19 ppm. Statistically significant differences were observed between time-weighted average exposure levels of Decon Sprayers and the other workers. Spraying of pH-adjusted bleach solution on subway tunnel surfaces for biological decontamination produced up to 50 ppm chlorine vapor in the air that far exceeded the occupational exposure limits of 0.5-1 ppm for chlorine, as well as the Immediately Dangerous to Life or Health limit of 10 ppm. Health and safety plans and operational activities must provide appropriate worker protection during such events where potential for chlorine overexposure has been demonstrated.

Chemical pneumonitis in a 9-year-old following chlorine gas exposure

A previously fit and well 9-year-old boy developed shortness of breath and chest pain after playing with friends on a building site where bonfire materials were being collected. Firstline investigations failed to explain his symptoms, which worsened over the next 24 hours, necessitating endotracheal intubation and mechanical ventilation. When public health and the police retraced his steps, they found barrels of sodium hypochlorite and red diesel at the bonfire site, which when mixed had the potential to form chlorine gas leading to the diagnosis of a chemical pneumonitis secondary to chlorine gas inhalation. Supportive care was continued, and he was successfully extubated after 48 hours. At 6-week follow-up, he had no ongoing pulmonary symptoms.

8-Isoprostane is an early biomarker for oxidative stress in chlorine-induced acute lung injury

Inhalation of chlorine (Cl₂) may cause oxidative acute lung injury (ALI) characterized by pulmonary edema, pneumonitis, and hyperreactive airways. The aim of the study was to identify possible biomarkers for Cl₂-induced ALI. Female BALB/c mice were exposed to Cl₂ for 15min using two protocols 1) concentration-dependent response (25-200ppm) and 2) time-kinetics (2h-14days post-exposure). Exposure to 50-200ppm Cl₂ caused a concentration-dependent inflammatory response with increased expression of IL-1β, IL-6 and CXCL1/KC in bronchoalveolar lavage fluid 2-6h after exposure which was followed by increased lung permeability and a neutrophilic inflammation 12-24h post-exposure. The early inflammatory cytokine response was associated with a clear but transient increase of 8-isoprostane, a biomarker for oxidative stress, with its maximum at 2h after exposure. An increase of 8-isoprostane could also be detected in serum 2h after exposure to 200ppm Cl₂, which was followed by increased levels of IL-6 and CXCL1/KC and signs of increased fibrinogen and PAI-1. Melphalan, a non-oxidizing mustard gas analog, did not increase the 8-isoprostane levels, indicating that 8-isoprostane is induced in airways through direct oxidation by Cl₂. We conclude that 8-isoprostane represents an early biomarker for oxidative stress in airways and in the blood circulation following Cl₂-exposure.

l-α-Phosphatidylglycerol Chlorohydrins as Potential Biomarkers for Chlorine Gas Exposure

Chlorine is a widely available toxic chemical that has been repeatedly used in armed conflict globally. The Organization for the Prohibition of Chemical Weapons (OPCW) have on numerous occasions found "compelling confirmation" that chlorine gas has been used against civilians in northern Syria. However, currently, there are no analytical methods available to unambiguously prove chlorine gas exposure. In this study, we describe the screening for chlorinated biomolecules by the use of mass isotope ratio filters followed by the identification of two biomarkers present in bronchoalveolar lavage fluid (BALF) from chlorine gas exposed mice. The relevance of these markers for human exposure was verified by their presence in in vitro chlorinated human BALF. The biomarkers were detectable for 72 h after exposure and were absent in nonexposed control animals. Furthermore, the biomarkers were not detected in humans diagnosed with chronic respiratory diseases. The potential chlorine specific markers were all chlorohydrins of unsaturated pulmonary surfactant phospholipids; phosphatidylglycerols, and phosphatidylcholines. Mass spectrometry fragmentation characteristics were favorable for the phosphatidylglycerol chlorohydrins, and they were therefore proposed as the best biomarker candidates.

N-acetyl cysteine improves the effects of corticosteroids in a mouse model of chlorine-induced acute lung injury

Chlorine (Cl2) causes tissue damage and a neutrophilic inflammatory response in the airways manifested by pronounced airway hyperreactivity (AHR). The importance of early anti-inflammatory treatment has previously been addressed. In the previous study, both high-dose and low-dose of dexamethasone (DEX) decreased the risk of developing delayed effects, such as persistent lung injuries, while only high-dose treatment could significantly counteract acute-phase effects. One aim of this study was to evaluate whether a low-dose of DEX in combination with the antioxidant N-acetyl cysteine (NAC) and if different treatments (Triptolide, Reparixin and Rolipram) administered 1h after Cl2-exposure could improve protection against acute lung injury in Cl2-exposed mice. BALB/c mice were exposed to 300 ppm Cl2 during 15 min. Assessment of AHR and inflammatory cells in bronchoalveolar lavage was analyzed 24h post exposure. Neither of DEX nor NAC reduced the AHR and displayed only minor effects on inflammatory cell influx when given as separate treatments. When given in combination, a protective effect on AHR and a significant reduction in inflammatory cells (neutrophils) was observed. Neither of triptolide, Reparixin nor Rolipram had an effect on AHR but Triptolide had major effect on the inflammatory cell influx. Treatments did not reduce the concentration of either fibrinogen or plasminogen activator inhibitor-1 in serum, thereby supporting the theory that the inflammatory response is not solely limited to the lung. These results provide a foundation for future studies aimed at identifying new concepts for treatment of chemical-induced lung injury. Studies addressing combination of anti-inflammatory and antioxidant treatment are highly motivated.

Chlorine gas exposure increases susceptibility to invasive lung fungal infection

Chlorine (Cl₂) is a highly irritating and reactive gas with potential occupational and environmental hazards. Acute exposure to Cl₂ induces severe epithelial damage, airway hyperreactivity, impaired alveolar fluid clearance, and pulmonary edema in the presence of heightened inflammation and significant neutrophil accumulation in the lungs. Herein, we investigated whether Cl₂ exposure affected the lung antimicrobial immune response leading to increased susceptibility to opportunistic infections. Mice exposed to Cl₂ and challenged intratracheally 24 h thereafter with the opportunistic mold Aspergillus fumigatus demonstrated an >500-fold increase in A. fumigatus lung burden 72 h postchallenge compared with A. fumigatus mice exposed to room air. Cl₂-exposed A. fumigatus challenged mice also demonstrated significantly higher lung resistance following methacholine challenge and increased levels of plasma proteins (albumin and IgG) in the bronchoalveolar lavage fluid. Despite enhanced recruitment of inflammatory cells to the lungs of Cl₂-exposed A. fumigatus challenged mice, these cells (>60% of which were neutrophils) demonstrated a profound impairment in generating superoxide. Significantly higher A. fumigatus burden in the lungs of Cl₂ exposed mice correlated with enhanced production of IL-6, TNF-α, CXCL1, CCL2, and CCL3. Surprisingly, however, Cl₂-exposed A. fumigatus challenged mice had a specific impairment in the production of IL-17A and IL-22 in the lungs compared with mice exposed to room air and challenged with A. fumigatus. In summary, our results indicate that Cl₂ exposure markedly impairs the antimicrobial activity and inflammatory reactivity of myeloid cells in the lung leading to increased susceptibility to opportunistic pathogens.

Complications of chlorine inhalation in a pediatric chemical burn patient: a case report

The majority of burn injuries in the pediatric population occur at home, and a significant proportion are the result of exposure to household cleaning products. A common injury-causing agent is bleach, which has the potential to release chlorine gas, a potent respiratory irritant that leads to the added risk of inhalation injury. The survival of pediatric patients with chemical burns is extremely high, and the 3 strongest predictors of mortality are large burn size, age <48 months, and the presence of inhalation injury. The authors present a rare case of a pediatric fatality from a chemical bleach burn that resulted in acute respiratory distress syndrome as well as hemodynamic and pulmonary instability that required extracorporeal membrane oxygenation. The authors critically appraised the management of this patient to determine the possible effect certain events had on the unexpected and poor outcome of this patient, including fluid resuscitation, the effect of the chemical inhalation injury, sedation, and the need for invasive extracorporeal membrane oxygenation life support.

Acute accidental exposure to chlorine gas in the Southeast of Turkey: a study of 106 cases

The present study reports a thorough investigation of the sociodemographic characteristics, clinical findings, and treatment of persons affected acutely by chlorine gas exposure from a chlorine tank belonging to the municipality of Diyarbakir. One hundred six persons were assessed. In this cross-sectional study, 58 patients were male and 48 were female. Children and adolescents younger than 18 years constituted more than half of the patients (60 cases, 56.6%). The age of patients ranged between 3 months and 75 years. Among the cases evaluated in emergency rooms, 7 patients had mild poisoning and were discharged after first examinations and symptomatic treatments, 62 patients were moderately affected and were taken under observation, and the remaining 37 were severely affected and were hospitalized. In physical examinations, 29 patients had expiratory wheezing, and 1 had tachycardia and extrasystoles. There were no deaths among these patients, acute chlorine intoxication affected mostly children. Respiratory tract findings were predominant in most of the patients. Steroid and bicarbonate applications were inadequate supportive therapies. Humidified O(2) and beta-agonist applications were most useful in the therapy of acute chlorine intoxication.

The Role of the Clinical Laboratory in Managing Chemical or Biological Terrorism

Background: Domestic and international acts of terrorism using chemicals and pathogens as weapons have recently attracted much attention because of several hoaxes and real incidents. Clinical laboratories, especially those affiliated with major trauma centers, should be prepared to respond rapidly by providing diagnostic tests for the detection and identification of specific agents, so that specific therapy and victim management can be initiated in a timely manner. As first-line responders, clinical laboratory personnel should become familiar with the various chemical or biological agents and be active participants in their local defense programs.

Approach: We review the selected agents previously considered or used in chemical and biological warfare, outline their poisonous and pathogenic effects, describe techniques used in their identification, address some of the logistical and technical difficulties in maintaining such tests in clinical laboratories, and comment on some of the analytical issues, such as specimen handling and personal protective equipment.

Content: The chemical agents discussed include nerve, blistering, and pulmonary agents and cyanides. Biological agents, including anthrax and smallpox, are also discussed as examples for organisms with potential use in bioterrorism. Available therapies for each agent are outlined to assist clinical laboratory personnel in making intelligent decisions regarding implementation of diagnostic tests as a part of a comprehensive defense program.

Summary: As the civilian medical community prepares for biological and chemical terrorist attacks, improvement in the capabilities of clinical laboratories is essential in supporting counterterrorism programs designed to respond to such attacks. Accurate assessment of resources in clinical laboratories is important because it will provide local authorities with an alternative resource for immediate diagnostic analysis. It is, therefore, recommended that clinical laboratories identify their current resources and the extent of support they can provide, and inform the authorities of their state of readiness.

Chemicals and gases

This article covers the major chemicals and gases that are considered to be of the most clinical relevance to the primary care provider. The reader is referred to other comprehensive textbooks of toxicology and occupational medicine for a complete discussion of the numerous additional products found in the workplace that may result in occupational exposure.