High-resolution CT in chronic pulmonary changes after mustard gas exposure

Gaining insights into chronic obstructive pulmonary disease exacerbation through emerging biomarkers and the chronic obstructive pulmonary disease assessment test score

Chronic obstructive pulmonary disease (COPD), a leading cause of mortality and morbidity, presents significant challenges, particularly with exacerbations, which drastically impact patients' health and healthcare costs. The Global Initiative for Chronic Obstructive Lung Disease guidelines recommend comprehensive assessments beyond spirometry, with the COPD assessment test (CAT) emerging as a pivotal tool. Despite its utility, the relationship between CAT scores and specific biomarkers during exacerbations remains unclear. Hence, this study aims to assess the correlation between the CAT score and specific circulating biomarkers. A cross-sectional study from August 2023 to January 2024 included 59 COPD patients with exacerbations who underwent pulmonary function tests and completed the CAT score assessment. The CAT score cut-off point was set at 20, where a CAT score <20 indicated a low impact on health status and a CAT score ≥20 indicated a high impact on health status. On the same day, measurements of neutrophils, leukocytes, eosinophils, C-reactive protein, and procalcitonin were conducted. Patients with CAT scores ≥20 had significantly higher levels of neutrophils (p=0.001), leukocytes (p=0.006), procalcitonin (p=0.010), and forced expiratory volume in the first second/forced vital capacity (p=0.002), but lower eosinophil levels (p=0.025). A positive correlation existed between total CAT score and neutrophils (p=0.001), leukocytes (p=0.000), and procalcitonin (p=0.010), while eosinophil levels showed a negative correlation (p=0.025). The spirometry parameters showed no correlation with the total CAT score. This study highlights the link between CAT and key inflammatory biomarkers, supporting the use of blood biomarkers to identify COPD patients at risk of exacerbations.

The predictive association between radiological findings and lung cancer development in patients exposed to sulfur mustard gas: 4 decades follow up of 719 victims

BACKGROUND

Respiratory diseases are the leading cause of morbidity and mortality in the survivors exposed to Sulfur Mustard (SM). The late abnormalities can be present as chronic bronchitis, tracheobronchial stenosis, asthma, bronchiectasis, airway narrowing, lung fibrosis, and lung cancers. This study aims to investigate the association between radiological findings and lung cancer development in patients exposed to sulfur mustard gas.

METHODS

We entered 719 victims exposed to SM during the Iran-Iraq war into our follow-up study in a consensus manner. They were periodically followed with Chest HRCT scans from 2001 to an interval of 2014-2019. The mean year interval between exposure and the last follow-up was 38 years. For confirming the lung cancer in those with evidence of malignancy in their imaging, fine needle aspiration/biopsy and/or surgical intervention were done.

RESULTS

Among 719 patients, 57% were free from any pathologic findings in their HRCT scan. Among the subjects who had the abnormal radiologic findings, Air Trapping (AT), Lung Fibrosis (LF), Bronchiectasis (B), and the evidence of lung cancer were found in 265 (36.9%), 207 (28.8%), 151 (21.0%), and 42 (5.8%), respectively. Adenocarcinoma (38.1%) was the most common type of cancer. The right lung was involved more than the left one regarding LF, B, and cancer (p value < 0.05). Considering the laterality, a significant correlation was found between the side of LF and B and the tumor side. Furthermore, it was shown that the lung lobes with LF were statistically correlated to tumor-involved lobes. The relative risk of AT and B existence for tumor development was 11.73 [4.87-28.26] and 10.14 [5.12-20.090], respectively. The most predictive finding was LF which caused the risk of developing tumor 17.75 [7.35-42.86] times higher in the patient with this pathology. By each increment of the number of LF and B, the risk of developing tumors increased by 51% and 76%, respectively.

CONCLUSION

In survivors exposed to Sulfur Mustard, those with bronchiectasis and lung fibrosis have a significantly higher risk of developing lung cancers, so a close follow-up of these victims is recommended. Trial registration This study was confirmed by the institutional review board and ethics committee at Shiraz University of Medical Sciences (SUMS) with the ethical code IR.SUMS.MED.REC.1399.637.

Are Iranian Sulfur Mustard Gas-Exposed Survivors More Vulnerable to SARS-CoV-2? Some Similarity in Their Pathogenesis

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that emerged as a health problem worldwide. It seems that COVID-19 is more lethal for Iranian veterans with a history of exposure to mustard gas. There are some similarities in the pathogenesis of SARS-CoV-2 and mustard gas in immune system disruption and pulmonary infection. SARS-CoV-2 and mustard gas inducing oxidative stress, immune system dysregulation, cytokine storm, and overexpression of angiotensin-converting enzyme II (ACE2) receptor in lungs that act as functional entry receptors for SARS-CoV-2. Moreover, Iranian survivors of mustard gas exposure are more susceptible and vulnerable to COVID-19. It is suggested that the principles of COVID-19 infection prevention and control be adhered to more stringently in Iranian survivors of mustard gas exposure than others who have not been exposed to mustard gas. Therefore, in this review, we discuss the different pathologic aspects of lung injury caused by mustard gas and also the relationship between this damage and the increased susceptibility of Iranian mustard gas exposed survivors to COVID-19.

Progressive Lung Injury, Inflammation, and Fibrosis in Rats Following Inhalation of Sulfur Mustard

Sulfur mustard (SM) inhalation causes debilitating pulmonary injury in humans which progresses to fibrosis. Herein, we developed a rat model of SM toxicity which parallels pathological changes in the respiratory tract observed in humans. SM vapor inhalation caused dose (0.2-0.6 mg/kg)-related damage to the respiratory tract within 3 days of exposure. At 0.4-0.6 mg/kg, ulceration of the proximal bronchioles, edema and inflammation were observed, along with a proteinaceous exudate containing inflammatory cells in alveolar regions. Time course studies revealed that the pathologic response was biphasic. Thus, changes observed at 3 days post-SM were reduced at 7-16 days; this was followed by more robust aberrations at 28 days, including epithelial necrosis and hyperplasia in the distal bronchioles, thickened alveolar walls, enlarged vacuolated macrophages, and interstitial fibrosis. Histopathologic changes were correlated with biphasic increases in bronchoalveolar lavage (BAL) cell and protein content and proliferating cell nuclear antigen expression. Proinflammatory proteins receptor for advanced glycation end product (RAGE), high-mobility group box protein (HMGB)-1, and matrix metalloproteinase (MMP)-9 also increased in a biphasic manner following SM inhalation, along with surfactant protein-D (SP-D). Tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS), inflammatory proteins implicated in mustard lung toxicity, and the proinflammatory/profibrotic protein, galectin (Gal)-3, were upregulated in alveolar macrophages and in bronchiolar regions at 3 and 28 days post-SM. Inflammatory changes in the lung were associated with oxidative stress, as reflected by increased expression of heme oxygenase (HO)-1. These data demonstrate a similar pathologic response to inhaled SM in rats and humans suggesting that this rodent model can be used for mechanistic studies and for the identification of efficacious therapeutics for mitigating toxicity.

Progressive delayed respiratory complications of sulfur mustard poisoning in 43 Iranian veterans, three decades after exposure

The most common delayed complication of sulfur mustard (SM) poisoning has been observed in the respiratory tracts. It was thus aimed to investigate the delayed respiratory complications in SM-exposed patients around 25 years before the study. Forty-three veterans with more than 25% disability of due to SM poisoning were investigated. Clinical examinations as well as pulmonary function test (PFT) were performed. High-resolution computed tomography (HRCT) of the lungs was done as clinically indicated. Triad of chronic cough, dyspnea, and expectoration were the most common symptoms that were recorded in 88.2%, 88.2%, and 64.7% of the patients, respectively. PFT abnormalities were detected in 44.18% of the patients. Restrictive pattern was the most common (41.86%), while pure obstructive pattern did not detect at all. Mixed pattern was significantly correlated with higher disability percentages among the veterans ( p < 0.001). Significant reverse correlation between the disability percentages and forced expiratory volume in 1 s/forced vital capacity ratio was obtained ( p = 0.010, r = −0.389). Air trapping was the most common abnormality in HRCTs (50%). Bronchiectasis (25%), pulmonary fibrosis (25%), and ground-glass attenuation (16.66%) were other common HRCT findings. Comparing with the previous studies on these patients, more restrictive and mixed pattern were observed. Moreover, bronchiolitis, bronchiectasis, and lung fibrosis were the main pathological findings in these patients.

NMR spectroscopy-based metabolomic study of serum in sulfur mustard exposed patients with lung disease

Sulfur mustard (SM) is a vesication chemical warfare agent for which there is currently no antidote. Despite years of research, there is no common consensus about the pathophysiological basis of chronic pulmonary disease caused by this chemical warfare agent. In this study, we combined chemometric techniques with nuclear magnetic resonance (NMR) spectroscopy to explore the metabolic profile of sera from SM-exposed patients. A total of 29 serum samples obtained from 17 SM-injured patients, and 12 healthy controls were analyzed by Random Forest. Increased concentrations of seven amino acids, glycerol, dimethylamine, ketone bodies, lactate, acetate, citrulline and creatine together with the decreased very low-density lipoproteins (VLDL) levels were observed in patients compared with control subjects. Our study reveals the metabolic profile of sera from SM-injured patients and indicates that NMR-based methods can distinguish these patients from healthy controls.

Long-term pulmonary complications of chemical weapons exposure in former poison gas factory workers

CONTEXT

Sulfur mustard (SM) and lewisite are vesicant chemical warfare agents that can cause skin blistering and chronic lung complications. During 1929-1945, a Japanese factory produced poisonous gases, which included SM, lewisite and other chemical weapons. The aim of this study was to investigate the chest computed tomography (CT) findings among long-term survivors who worked at this factory.

METHODS

During 2009-2012, we evaluated chest CT findings from 346 long-term survivors who worked at the poison gas factory. Skin lesions were used as an indicator of significant exposure to vesicant agents.

RESULTS

Among the 346 individuals, 53 (15%) individuals experienced skin lesions while working at the factory, and chest CT revealed abnormal findings in 179 individuals (52%). Emphysema was the most common CT finding and was observed in 75 individuals (22%), while honeycombing was observed in 8 individuals (2%). Emphysema and honeycombing were more prevalent among individuals with skin lesions, compared to individuals without skin lesions. Multivariate analyses revealed significant associations between the presence of emphysema and skin lesions (p = 0.008). Among individuals who never smoked, individuals with skin lesions (n = 26) exhibited a significantly higher rate of emphysema, compared to individuals without skin lesions (n = 200) (35% versus 7%, respectively; p < 0.001).

CONCLUSION

Among the long-term survivors who worked at the poison gas factory, a history of skin lesions was associated with the presence of emphysema, even among never smokers, which suggests that emphysema might be a long-term complication of exposure to chemical warfare agents.

A review on delayed toxic effects of sulfur mustard in Iranian veterans

Iranian soldiers were attacked with chemical bombs, rockets and artillery shells 387 times during the 8-years war by Iraq (1980-1988). More than 1,000 tons of sulfur mustard gas was used in the battlefields by the Iraqis against Iranian people. A high rate of morbidities occurred as the result of these attacks. This study aimed to evaluate the delayed toxic effects of sulfur mustard gas on Iranian victims. During a systematic search, a total of 193 (109 more relevant to the main aim) articles on sulfur mustard gas were reviewed using known international and national databases. No special evaluation was conducted on the quality of the articles and their publication in accredited journals was considered sufficient. High rate of morbidities as the result of chemical attacks by sulfur mustard among Iranian people occurred. Iranian researchers found a numerous late complications among the victims which we be listed as wide range of respiratory, ocular, dermatological, psychological, hematological, immunological, gastrointestinal and endocrine complications, all influenced the quality of life of exposed victims. The mortality rate due to this agent was 3%. Although, mortality rate induced by sulfur mustard among Iranian people was low, variety and chronicity of toxic effects and complications of this chemical agent were dramatic.

Mustard gas toxicity: the acute and chronic pathological effects

Ever since it was first used in armed conflict, mustard gas (sulfur mustard, MG) has been known to cause a wide range of acute and chronic injuries to exposure victims. The earliest descriptions of these injuries were published during and in the immediate aftermath of the First World War, and a further series of accounts followed the Second World War. More recently, MG has been deployed in warfare in the Middle East and this resulted in large numbers of victims, whose conditions have been studied in detail at hospitals in the region. In this review, we bring together the older and more recent clinical studies on MG toxicity and summarize what is now known about the acute and chronic effects of the agent on the eyes, skin, respiratory tract and other physiological systems. In the majority of patients, the most clinically serious long-term consequences of MG poisoning are on the respiratory system, but the effects on the skin and other systems also have a significant impact on quality of life. Aspects of the management of these patients are discussed.

Noninvasive diagnosis of bronchiolitis obliterans due to sulfur mustard exposure: could high-resolution computed tomography give us a clue?

PURPOSE

Previous pathological investigations have reported bronchiolitis obliterans (BO) as the major long-term sequela of exposure to sulfur mustard. In this study, we investigated whether high-resolution computed tomography (HRCT) could be used as a noninvasive imaging modality to differentiate between mustard lung (as a subtype of BO) and other respiratory disorders.

MATERIALS AND METHODS

Three groups of patients with sulfur-mustard-induced lung injury (BO), severe chronic asthma (resistant asthma) and smoking habit, respectively, were recruited. Also 30 nonsmoking participants were recruited randomly as the control group. Pulmonary function tests (PFT) and HRCT were performed. Images were viewed with a window level of -450 and window width of 1,400 HU. All images were evaluated by an expert radiologist who was blinded regarding the patients' diagnoses and clinical situations.

RESULTS

Airway involvement was higher and more frequent than parenchymal involvement in the groups with chemical-induced injury and asthma in comparison with smokers. On the other hand, parenchymal involvement was more frequent than airway involvement in the smokers' group in comparison with the other groups.

CONCLUSIONS

HRCT can be a very useful method for differentiating between mustard lung, resistant asthma and lung injuries due to cigarette smoking.

Development and validation of automated 2D-3D bronchial airway matching to track changes in regional bronchial morphology using serial low-dose chest CT scans in children with chronic lung disease

To address potential concern for cumulative radiation exposure with serial spiral chest computed tomography (CT) scans in children with chronic lung disease, we developed an approach to match bronchial airways on low-dose spiral and low-dose high-resolution CT (HRCT) chest images to allow serial comparisons. An automated algorithm matches the position and orientation of bronchial airways obtained from HRCT slices with those in the spiral CT scan. To validate this algorithm, we compared manual matching vs automatic matching of bronchial airways in three pediatric patients. The mean absolute percentage difference between the manually matched spiral CT airway and the index HRCT airways were 9.4 ± 8.5% for the internal diameter measurements, 6.0 ± 4.1% for the outer diameter measurements, and 10.1 ± 9.3% for the wall thickness measurements. The mean absolute percentage difference between the automatically matched spiral CT airway measurements and index HRCT airway measurements were 9.2 ± 8.6% for the inner diameter, 5.8 ± 4.5% for the outer diameter, and 9.9 ± 9.5% for the wall thickness. The overall difference between manual and automated methods was 2.1 ± 1.2%, which was significantly less than the interuser variability of 5.1 ± 4.6% (p<0.05). Tests of equivalence had p<0.05, demonstrating no significant difference between the two methods. The time required for matching was significantly reduced in the automated method (p<0.01) and was as accurate as manual matching, allowing efficient comparison of airways obtained on low-dose spiral CT imaging with low-dose HRCT scans.

Exercise intolerance and chronotropic impairment-The long-term cardiovascular sequelae of mustard gas exposure: A paired-comparative study

BACKGROUND

Although there are some data regarding the pulmonary manifestations of mustard gas exposure, little is known about its cardiovascular sequelae.

METHODS

The spirometric and exercise tolerance test results of two groups of patients with chronic bronchitis one with (group A) and one without (group B) previous exposure to mustard gas and a group of veterans with no bronchitis (group C) were compared.

RESULTS

The exercise capacity was similar in groups "A" and "B" patients. Both groups, showed a remarkable impairment of exercise capacity (p<0.001) compared to the group "C" individuals. Although the mean resting heart rate was significantly higher in group "A" patients than group "B" individuals (p=0.01), their mean peak exercise heart rate was significantly lower (p=0.01). Both groups, however, achieved a significant lower peak exercise heart rates, compared to the group "C" subjects (p<0.001).

CONCLUSION

Mustard gas exposure can limit the exercise capacity and abolish the normally expected chronotropic response to exercise.

Inspiratory and expiratory high-resolution computed tomography (HRCT) in patients with chemical warfare agents exposure

Chemical warfare agents (CWA) including sulfur mustard (SM) were commonly used in Iran-Iraq war. Respiratory problems are the greatest cause of long-term disability among people who had combat exposure to SM. High-resolution computed tomography (HRCT) has been accepted as the imaging modality of choice in these patients. We used expiratory HRCT findings in comparison to inspiratory HRCT for demonstration of pulmonary damage in these patients. HRCT in deep inspiration as well as full expiration was performed in 473 patients with a history of chemical gas exposure during the war and the results were compared. The study was prospective during 1 yr. Of 473 patients, 366 (77.38%) showed normal HRCT in deep inspiration; however, on corresponding expiratory cuts, 263 (71.86%) had abnormalities. The most frequent abnormal finding in expiration was patchy air trapping (77.77%). We conclude that exposure to SM causes pulmonary complications resulting in disability in the affected patients; however, HRCT in inspiration is normal in most of the affected patients. Expiratory HRCT showed patchy air trapping as the most common finding, which is suggestive of small air way diseases such as bronchiolitis obliterans; therefore it is recommended to do HRCT both in deep inspiration and full expiration in patients with a history of CWA exposure.

Late respiratory effects of sulfur mustard: how is the early symptoms severity involved?

The association between severity of exposure to sulfur mustard (SM) and late respiratory complications is not clear. The aim of this study was to determine the presence of late pulmonary complications in patients with mild, moderate, and severe initial symptoms of sulfur mustard exposure. This was a retrospective cohort study on patients with mild, moderate, and severe initial symptoms of sulfur mustard exposure (during 1983–1988) in Baqyatallah University of medical sciences (2004–2005). The ‘mild’ group ( n = 115) had no early symptom at the time of exposure. The ‘moderate’ group ( n = 273) had early symptoms after exposure and were not hospitalized for that reason. The ‘severe’ group ( n = 215) had early symptoms and had been hospitalized accordingly. Pulmonary function tests and high-resolution computed tomography of the chest were performed. The chi-square test was used for data analysis. The severe and moderate groups had a similar frequency of obstructive pattern (21%), whereas only one patient in the mild group showed this pattern. Air trapping did not significantly differ between groups. In the mild group, 74.8% ( n = 86) showed significant air trapping, whereas it was 62.3% ( n = 170) in moderate and 67.0% ( n = 144) in severe groups ( P = 0.057). Moderate and severe exposure to sulfur mustard causes an equal risk of late pulmonary complications, while mild exposure has lesser risk. Bronchiolitis obliterans is the main underlying respiratory consequence of sulfur mustard exposures and may relate to host factors rather than to severity of early symptoms.

Long term consequences from exposure to sulfur mustard: a review

Mustard gas (HD) was a widely used chemical warfare agent during World War I and more recently in the Iraq-Iran war (1980-1988). To date, dramatically, 45,000 Iranians are suffering from late respiratory complications due to MG exposure. This review covers two decades of researches on latent pulmonary effects of MG. Findings from clinical manifestations, pathologic examinations, laboratory data, lung function tests, and radiological evaluations are reviewed. From this review we are able to provide a suitable practical plan for workup and management of patients in this setting.

Mustard lung secrets: long term clinicopathological study following mustard gas exposure

Considering the undefinite nature of lung pathology in patients exposed to sulfur mustard (SM) many years after exposure, we conducted this study to document and quantify lung disease in this setting. In a cross sectional study, we selected 23 patients exposed to SM gas approximately 14 years ago during the Iran-Iraq war (1980-1988). We studied their clinical history, physical examination, pulmonary function test (PFT), high-resolution computed tomography scan (HRCT) of the chest, bronchoscopy, and bronchoalveolar lavage (BAL) sampling, and transbronchial lung biopsies. Other potential causes of lung disease, including smoking of cigarettes, were excluded. All 23 patients were symptomatic with cough, dyspnea, and/or felt tight in the chest. All of them had significant air trapping in HRCT and a marked increase of residual volume in PFT. The most common inflammatory cell in BAL fluid was neutrophil (88%). Of the 23 cases, there was sufficient tissue for detailed evaluation in 22. Histologically, 11 cases showed airway epithelial injury, and nine of the 14 lung biopsies with alveoli had histopathological changes diagnosable as organizing pneumonia (OP) or bronchiolitis obliterans OP (BOOP). Two out of 14 cases showed changes suggestive of OP. Inhalation of SM can lead to persistant and clinically significant lung disease, including bronchial mucosal injury and OP, many years after exposure.

Tracheobronchomalacia and Air Trapping after Mustard Gas Exposure

RATIONALE

Mustard gas primarily affects the eyes, skin, and particularly the respiratory tract. Tracheobronchomalacia (TBM) and air trapping are often observed in high-resolution computerized tomography (HRCT) scans of the chest of mustard gas-exposed patients.

OBJECTIVES

To examine the frequency and severity of TBM in a group of Iranian wartime mustard gas-exposed victims, and to investigate the correlation between TBM and air trapping in these cases.

MATERIALS AND METHODS

Chest HRCT films obtained from 300 randomly selected subjects who had been exposed to mustard gas 15.5 yr previously were reviewed to determine the existence of TBM and air trapping. The HRCT films of a healthy control group were also analyzed for comparison.

RESULTS

Out of 300 reviewed cases, 13 had TBM. From these 13 TBM cases, 11 (85%) showed air trapping with mean score of 5.5. In the control group, 5 (25%) of 20 subjects showed air trapping, with mean score of 0.6. The total air trapping was significantly higher in the TBM group (p < 0.001). There was an association between the severity of tracheomalacia and air trapping in the TBM group (p = 0.01, r = 0.69), but no association was observed between severity of bronchomalacia and air trapping.

CONCLUSION

The results show that air trapping and TBM are correlated, both as long-term sequelae in mustard gas-exposed cases. Because air trapping is highly suggestive of bronchiolitis obliterans, we conclude that both bronchiolitis obliterans and TBM are caused by a single underlying process affecting small and large airways, respectively, in this group of patients.

Bronchiolitis obliterans following exposure to sulfur mustard: chest high resolution computed tomography

BACKGROUND

Pulmonary complications are known to occur in over half of the patients exposed to sulfur mustard (SM). Chemical weapons of mass destruction (WMD) including SM were used by Iraq during Iran-Iraq war between 1983 and 1989. We undertook this study to evaluate the chest high resolution computerized tomography (HRCT) as a diagnostic tool in patients with documented exposure to SM and chronic respiratory symptoms.

METHOD

The medical records of 155 patients exposed to SM during Iran-Iraq war and suffered respiratory complications were reviewed. Chest HRCTs of these patients were examined. Ten healthy controls with no history of exposure to HD were matched for age, gender, and chest HRCT protocol applied.

RESULTS

Fifty chest HRCTs of these patients were randomly selected for this study. The most frequent findings were; air trapping 38 (76%), bronchiectasis 37 (74%), mosaic parenchymal attenuation (MPA) 36 (72%), irregular and dilated major airways 33 (66%) bronchial wall thickening (BWT) 45 (90%), and interlobular septal wall thickening (SWT) 13 (26%), respectively. Air trapping in one patient (10%) was the only positive finding in the control group.

CONCLUSIONS

Chest HRCT findings of bronchiectasis, air trapping, MPA, SWT, and BWT were seen in our patients 15 years after exposure to HD. These findings suggest the diagnosis of bronchiolitis obliterans (BO). We did not encounter chest HRCT features consistent with pulmonary fibrosis.

Incidence of Lung, Eye, and Skin Lesions as Late Complications in 34,000 Iranians With Wartime Exposure to Mustard Agent

Approximately 34,000 Iranians known to have sustained mustard agent exposure during the Iran-Iraq war of 1980-1988 and survived over a decade afterwards were screened for distribution of the most commonly occurring medical problems. In order of greatest incidence, these include lesions of the lungs (42.5%), eyes (39.3%), and skin (24.5%). Within each subpopulation, patients were ranked according to severity of lesions. Twenty-three percent to 37% of patients exhibited at least mild coverage, with 1.5% to 4.5% classed as moderate, and a much smaller population (0.023-1.0%) of the 34,000 patients exhibiting extensive (severe) lesional coverage. These results provide a comprehensive overview of the medical problem most common among mustard victims and could serve as a predictor of the likely impact of these weapons on health status of populations exposed to them during ongoing military conflicts.