Risk Assessment Of Occupational Exposure Research Articles

221 Risk assessment of occupational exposure to graphene nanoforms - Where are we?

221 Risk assessment of occupational exposure to graphene nanoforms - Where are we?

Exposure and Early Effect Biomarkers for Risk Assessment of Occupational Exposure to Formaldehyde: A Systematic Review

The aim of the present review was to identify all the biomarkers used for assessing the internal dose and the related early effects determined by the occupational exposure to formaldehyde. For this purpose, a systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The protocol was registered in PROSPERO (ID: CRD42023416960). An electronic search of Pubmed, Scopus, and Web of Science was performed to collect all the papers concerning the focus of the review and published from the inception of each database until 18 September 2023. Articles were considered eligible if they reported data from observational studies, semi-experimental, and experimental studies on adult workers who were occupationally exposed to formaldehyde, regardless of gender or age. The quality assessment was performed using the adapted Newcastle–Ottawa Quality Assessment Scale. From 1524 articles, 52 were included. Few studies assessed the exposure to formaldehyde in occupational settings through biomarkers, especially by measuring formic acid in urine. The most common approach for evaluating the effects derived from occupational exposure to formaldehyde was the use of the cytogenetic biomarker micronucleus assay in peripheral blood lymphocytes and/or epithelial buccal cells.

Health risk assessment of occupational exposure to heavy metals among green space workers in Iran.

Exposure to heavy metals can result in various adverse health effects. Tehran is rated as one of the world's most polluted cities. Green space workers are continuously exposed to such pollutants in this city. Thus, this study aimed to estimate the health risks caused by exposure to heavy metals among green space workers. Eighty-eight workers and office personnel in two regions with different air quality levels were chosen for sampling. Air samples were collected using the NIOSH-7300 method and analyzed using an Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) instrument. The hazard quotient (HQ) and the lifetime cancer risk (LTCR) were calculated to assess carcinogenic and non-carcinogenic risk levels. The results revealed that the rank order of heavy metals was determined as Zn, Pb, Mn, Ni, Co, and Cd. Workers were subjected to higher concentrations of Ni, Pb, Zn, and Co than office personnel. Furthermore, the Cd, Co, and Zn exposure levels stood significantly higher in region 6 than in region 14. Non-carcinogenic risk levels for all participants fell within the acceptable range. Moreover, no employee had a carcinogenic risk level within the acceptable range when exposed to Cd. Also, 2.3% of individuals demonstrated Ni's acceptable carcinogenic risk level. Owing unacceptable risk levels, proper interventions are required to minimize occupational exposure to heavy metals. These interventions include optimizing shift schedules, using personal protective equipment, and conducting regular health assessments.

Risk assessment of occupational exposure to engineered and incidental nanomaterials: differences and challenges

Risk assessment of occupational exposure to engineered and incidental nanomaterials: differences and challenges

Health Risk Assessment of Occupational Exposure to Chemical Materials in a Combined-Cycle Power Plant

Background: This study aimed to evaluate the occupational exposure of workers at a combined-cycle power plant located in the southwestern region of Iran. The assessment focuses on the inhalation exposure route to workplace emissions. Methods: The primary locations for potential pollutant emissions were identified in close proximity to the areas where chemicals were introduced and utilized within the production process. Sulfuric acid, sodium hydroxide, ammonia, oil mist, toluene, hydrogen sulfide, hydrazine, and tetrachloromethane were measured and analyzed using the NIOSH standard. Dose-response assessment was estimated using inhalation unit risk (IUR) for cancer risks and reference concentration (RFC) and reference exposure levels (REL) for non-cancer risks. Risk assessment was performed based on the Environmental Health Hazard Assessment guideline. Results: The results showed that ammonia and toluene had the highest and lowest concentration of pollutants emitted in workplace, respectively. The inhalation of ammonia and sulfuric acid and their daily absorption were at high risk level (HQ>1). Other noncancerous compounds had HQ<1. While the hazard index (HI) for total non-cancer risks was 5.34E+01 (HI>1), it was likely to have non-cancerous risks. For carcinogenic risks, they were calculated to be 9.58E-03 and 5.47E-04 for hydrazine and tetrachloromethane, respectively. The total carcinogenic risk of the emissions was calculated at 1.01E-02, which was in the significant range (more than 10-4) (i.e. in the range of hazardous cancer effects). Conclusion: This study confirmed the presence of non-carcinogenic risks, while the quantity of cancer risks fell within the Significant range, indicating a potential for carcinogenic risks.

Occupational risk factors associated with Covid-19 among Health Workers in a tertiary referral Hospital, Nairobi Kenya: A case control study

Background: Covid-19 disease disproportionately affected health workers (HWs) by worsening the preexisting shortage of HWs in developing countries , thus overwhelming health systems and disrupting health delivery. However, evidence on the predominant sources of Covid-19 exposure among HWs in sub-Saharan Africa remains scarce. This study sought to identify the occupational risk factors associated with Covid-19 disease among HWs in a tertiary hospital in Kenya. Methods: An unmatched case-control study design was used to assess exposure differences between 39 randomly sampled PCR Covid-19 positive HWs (cases) and 108 conveniently sampled PCR Covid-19 negative and asymptomatic HWs(controls). An adapted WHO risk assessment questionnaire was administered via phone interviews to measure occupational exposure in the last two weeks before each participant’s PCR Covid-19 test between November 2021 and December 2021. Multivariable logistic regression was applied to identify the statistically significant risk factors and the results on adjusted Odds Ratio (aOR) were reported at 95% Confidence Intervals (P<0.05). Results: Controlling for the sex and the clinical status, sub-optimal adherence to face shields ((aOR 4,p<0.05), suboptimal infection prevention control (IPC) adherence in common staff dining rooms (aOR 8,p<0.05), working in medium risk departments (aOR 7,p<0.05) in the last 2 weeks before PCR Covid-19 testing were the significant occupational risk factors to Covid-19 disease among HWs. Conclusions: Reinforcing adherence to facial protective gears together with other personal protective equipment and promoting adherence to infection prevention protocols among HWs in occupational areas with perceived lower risk of infectious disease such as common hospital rooms can reduce the spread of Covid-19 among HWs. Future validation of occupational exposure risk assessment tool across different hospital and health delivery settings can improve comparability and generalizability of findings to inform policies for optimal protection of HWs during SARSCoV2 and similar infectious disease pandemics.

Occupational exposure to inhalable pathogenic microorganisms in waste sorting

This study assessed microorganisms in personal inhalable work air samples aiming to identify potential human pathogens, and correlate exposure to adverse health outcomes in waste workers. Full-shift personal exposure was measured in six different waste sorting plants. Microbial concentrations in inhalable air samples were analysed using MALDI-TOF MS for cultivable, and next generation sequencing (NGS) for non-cultivable microorganisms. Concentrations of bacterial and fungal CFUs varied substantially within and between waste sorting plants, ranging from no identifiable organisms to a maximum concentration in the order of 105 CFU/m3. Bacillus and Staphylococcus were among the most abundant bacterial genera, whilst fungal genera were dominated by Aspergillus and Penicillium. Approximately 15% of all identified species were human pathogens classified in risk group 2, whereas 7% belonged to risk group 1. Furthermore, significant correlations between concentrations of fungi in risk group 1 and self-reported adverse symptoms, such as wheezing were identified in exposed workers. The combination of culture-based methods and NGS facilitated the investigation of infectious microbial species with potential pathophysiological properties as well as non-infectious biological agents in inhalable work air samples and thereby contributed to the risk assessment of occupational exposure in waste sorting.

Probabilistic health risk assessment of occupational exposure to BTEX in a paint manufacturing plant using Monte-Carlo simulation

This study assessed the health risks of paint industry workers exposed to benzene, toluene, ethylbenzene, and xylene (BTEX) compounds using a probabilistic approach. Air samples were collected using charcoal tubes according to the NIOSH 1501 method and analyzed by a GC-FID. The EPA risk assessment model was used to assess the lifetime carcinogenic and non-carcinogenic risks posed by BTEX. A sensitivity analysis was performed to clarify the influence of input parameters on the health risks. In the paint production, paint packing, and thinner packing workshops, the concentration of at least two aromatic compounds exceeded the occupational exposure limit. Ethylbenzene posed greater carcinogenic risks than benzene. The individual and total cancer risk of benzene and ethylbenzene exceeded the 1E–4 level, indicating a definite cancer risk in all workshops of the factory. The mean of total non-cancer risk exceeded the standard (hazard index = 1) in all workshops with xylene as the most contributing aromatics in non-cancer risk. Putty production (428.5), thinner packing (340.79), and spray paint packing (148.45) were the workshops with the greatest hazard index. Sensitivity analysis indicated that the concentration of ethylbenzene and xylene contributed the most to cancer (73.0%) and non-cancer (87.8%) risks. These findings can help managers better understand BTEX-related risks faced by paint manufacturing workers and the need to control BTEX contamination to reduce health risks below the standard in paint industry.

Quantitative risk assessment of occupational exposure to PCDD/Fs in the waste incineration industry

Objective: To analyze the level of PCDD/Fs exposure of occupational workers in the waste incineration industry and explore the risk of occupational exposure. Methods: In September 2021, literature on environmental PCDD/Fs exposure in waste incineration plants published from the establishment of the database to February 10, 2021 was retrieved from CNKI database. A total of 1365 literatures were retrieved, and 7 met the criteria for inclusion. The US Environmental Protection Agency (EPA) inhalation risk model was used to assess and analyze carcinogenic and non-carcinogenic risks of PCDD/Fs exposure among occupational workers in the waste incineration industry. Results: A total of 86 sampling sites were included in incineration plants in 7 regions. The study of Wuhan area showed that the concentration of working environment near the waste incinerator in the same factory was the highest, followed by the rest and office area in the factory. The concentration of PCDD/Fs in waste incinerators was the highest in Southwest China (4880.00-24880.00 pg TEQ/m(3)), and the lowest in Shenzhen (0.02-0.44 pg TEQ/m(3)). According to the cancer risk assessment, with the increase of exposure years, the risk of cancer increased. The highest risk of cancer was found in the waste incineration plants in Southwest China. When the exposure period was 1 year, the risk was moderate (22.40×10(-6)-114.20×10(-6)). When the exposure time was more than 5 years, the risk of cancer was high. In Jinan, workers working near the incinerator had a moderate risk of cancer after five years of exposure. In Zhejiang, workers were at medium risk of cancer after exposure for more than 20 years. Workers in Wuhan, Shanghai, Zhejiang Province, Shenzhen and the Pearl River Delta were still at low risk of cancer after 40 years of occupational exposure. HQ>1 of workers working near the waste incinerators in Jinan, Zhejiang Province and Southwest China, and the qualitative evaluation results showed that the non-carcinogenic risk was unacceptable. Conclusion: There are great differences in PCDD/Fs of occupational exposure in waste incineration industry, and the occupational exposure exceeding the occupational exposure limit has higher carcinogenic and non carcinogenic risks.

Molecular mechanism of two functional protein structure changes under 2,3-butanedione-induced oxidative stress and apoptosis effects in the hepatocytes

Food security has become closely watched with the occurrence of a series of food safety incidents in recent years. The widespread adoption of 2,3-butanedione (BUT), as a food additive, is an unpreventable significant risk factor to food security. Based on this, mouse hepatocyte AML-12 cells and two functional proteins (bovine serum albumin and lysozyme) were utilized as targeted receptors to study the adverse effects of BUT at the cellular and molecular levels. Results suggested that BUT could disrupt the redox balance of AML-12 cells, reducing glutathione (GSH) activity fell to 87.18 %, which cannot offset the production of reactive oxygen species (ROS). Meanwhile, the increasement of lipid peroxidation and malondialdehyde (MDA) levels were observed. The mitochondrial membrane function was also abnormal due to the excessive accumulation of ROS and eventually leads to cell apoptosis and death. At the molecular level, the exposure of BUT could alter the skeleton and secondary structure of bovine serum albumin (BSA) and lysozyme (LYZ), and it could statically quench the intrinsic fluorescence of proteins. The combined experiments confirmed proved the potentially toxic effects of BUT accumulation on the detoxification organ, providing theoretical support for the liver diseases caused by BUT exposure, and a reference for the risk assessment of occupational exposure of BUT.

Probabilistic health risk assessment of occupational exposure to crystalline silica in an iron foundry in Urmia, Iran.

This study aimed to quantify the exposure of foundry workers to crystalline silica and associated cancer and non-cancer health risks using a probabilistic approach. Breathing zone air samples were collected according to the NIOSH 7602 method and analyzed using Fourier transform infrared spectroscopy. The health risks posed by crystalline silica were then assessed using the EPA-developed inhalation risk assessment model and Monte Carlo simulation. The sensitivity analysis was also conducted to determine the contribution of input parameters to the health risks. The mean concentration of crystalline silica in six foundry stations ranged from 0.029 to 0.064mgm-3, exceeding the occupational exposure limits. The average values of cancer risks were greater than the USEPA level, i.e., 1E - 6 in all workstations of the foundry. Workers in sand preparation and molding stations suffered the greatest cancer risks, with the mean value of 2.35E - 5 and 2.10E - 5, respectively. Non-cancer hazard quotient exceeded 1 in all foundry stations ranging from 1.56 (in melting and pouring) to 3.37 (in sand preparation). The 95% upper-bound values of the health risks decreased by 77.52% and 56.77%, assuming the use of engineering controls and wearing respirators by workers, respectively. Sensitivity analyses indicate that concentration was the most sensitive factor contributing to the carcinogenic (46.13%) and non-carcinogenic (67.08%) risks. These findings can aid managers in gaining a better understanding of the silica risks faced by foundry workers and the role of engineering controls and respirators in protecting workers' health.

A Qualitative and Quantitative Occupational Exposure Risk Assessment to Hazardous Substances during Powder-Bed Fusion Processes in Metal-Additive Manufacturing

Metal-additive manufacturing (AM), particularly the powder-bed fusion (PBF) technique, is undergoing a transition from the short-run production of components to higher-volume manufacturing. The industry’s increased production efficiency is paired with a growing awareness of the risks related to the inhalation of very fine metal powders during PBF and AM processes, and there is a pressing need for a ready-to-use approach to assess the risks and the occupational exposure to these very final metal powders. This article presents a study conducted in an AM facility, which was conducted with the aim to propose a solution to monitor incidental airborne particle emissions during metal AM by setting up an analytical network for a tailored approach to risk assessment. Quantitative data about the respirable and inhalable particle and metal content were obtained by gravimetric and ICP-MS analyses. In addition, the concentrations of airborne particles (10–300 nm) were investigated using a direct reading instrument. A qualitative approach for risk assessment was fulfilled using control banding Nanotool v2.0. The results show that the operations in the AM facility are in line with exposure limit levels for both micron-sized and nano-sized particles. The particulate observed in the working area contains metals, such as chromium, cobalt, and nickel; thus, biological monitoring is recommended. To manage the risk level observed for all of the tasks during the AM process, containment and the supervision of an occupational safety expert are recommended to manage the risk. This study represents a useful tool that can be used to carry out a static evaluation of the risk and exposure to potentially harmful very fine metal powders in AM; however, due to the continuous innovations in this field, a dynamic approach could represent an interesting future perspective for occupational safety.

Health Risk Assessment of Occupational Exposure of Refinery Unit Site Workers to BTEX in an Oil Refinery Company

Health Risk Assessment of Occupational Exposure of Refinery Unit Site Workers to BTEX in an Oil Refinery Company

The exposures and health effects of benzene, toluene and naphthalene for Chinese chefs in multiple cooking styles of kitchens.

Commercial cooking has higher intensity and more severe instantaneous cooking pollution from volatile organic chemicals compared to home cooking, making health risk assessment of occupational exposure for chefs a priority. In this study, chefs from three cooking styles of kitchens, including steaming, frying, and grilling, were selected to investigate the external and internal exposures, health risks and effects of several typical aromatic hydrocarbons (benzene, toluene and naphthalene). Naphthalene was found to be the most concentrated contaminant in air samples among the different kitchens, while benzene had the lowest concentration. The concentration of toluene in frying kitchens was significantly higher than that in steaming kitchens. Air concentrations of toluene in frying kitchens, as well as benzene concentrations in grilling kitchens exceeded the standard level according to indoor air quality standard (GB/T18883-2002). Regarding the metabolites of pollutants in urine, the content of S-benzylmercapturic acids (S-BMA) for frying chefs was significantly higher than that for other cooking styles of chefs, which was consistent with the relatively higher air concentrations of toluene. There was a good correlation between internal and external exposure of the pollutants. The level of oxidative stress was influenced by 2-hydroxynaphthalene (2-OHN) and S-BMA, indicating the potential health risks of these occupational exposed chefs. This study indicates the need to improve the monitoring of typical aromatic hydrocarbons, as well as to investigate their potential health effects in large-scale groups, and improve the ventilation in kitchens.

Health Risk Assessment of Occupational Exposure to Hexavalent Chromium in Iranian Workplaces: a Meta-analysis Study.

Occupational exposure to hexavalent chromium (Cr+6) has reported in different industries. The Cr6+ has the carcinogenic and non-carcinogenic effects. The aim of this study was to provide a meta-analysis and health risk assessment of occupational exposure to Cr6+ in Iranian workplaces. Databases including Scopus, Web of Sciences (WOS), and Scientific Information Database (SID), as a national database, were searched from 2000 to February 2021. The related studies to occupational exposure to Cr6+ were selected by Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. Lung cancer and non-cancer risk (nasal mucosal irritation, atrophy, and perforation) of Cr6+ were estimated by Environmental Protection Agency (EPA) method, based on the Monte Carlo simulation (MCS). Also, the results of spirometry and biomonitoring of previous studies were reviewed. We found 14 articles based on inclusion criteria. Pooled concentration of Cr6+ was estimated 0.037 ± 0.002mg/m3 which was higher than the recommended exposure limit by the ACGIH (0.002mg/m3). The mean lung cancer risk was estimated to be 5.49E-2, which was considerable risk. In the Cr6+-exposed workers, all parameters of pulmonary function had decreased. The level of Cr6+ in urinary and blood samples was higher than threshold limit. Results indicated that exposure to Cr6+ and its health risk were more than recommended exposure limit. The results of present study could be helpful for health policy maker to control exposure to Cr6+ in workplaces.

Characteristics and risk assessment of occupational exposure to ultrafine particles generated from cooking in the Chinese restaurant

Ultrafine particles have been increasingly linked to adverse health effects in restaurant workers. This study aimed to clarify the exposure characteristics and risks of ultrafine particles during the cooking process, and to provide a reasonable standard for protecting the workers in the Chinese restaurant. The temporal variations in particle concentrations (number concentration (NC), mass concentration (MC), surface area concentration (SAC), and personal NC), and size distributions by number were measured by real-time system. The hazard, exposure, and risk levels of ultrafine particles were analyzed using the control banding tools. The NC, MC, and SAC increased during the cooking period and decreased gradually to background levels post-operation. The concentration ratios of MC, total NC, SAC, and personal NC ranged from 3.82 to 9.35. The ultrafine particles were mainly gathered at 10.4 and 100 nm during cooking. The exposure, hazard and risk levels of the ultrafine particles were high. These findings indicated that the workers during cooking were at high risk due to exposure to high levels of ultrafine particles associated with working activity and with a bimodal size distribution. The existing control strategies, including engineering control, management control, and personal protection equipment need to be improved to reduce the risk.

Health risk assessment of occupational exposure to heavy metals in a steel casting unit of a steelmaking plant using Monte-Carlo simulation technique.

The present work aimed to evaluate the health risks of occupational exposure to heavy metals in a steel casting unit of a steel plant. To determine occupational exposure to heavy metals, personal air samples were taken from the workers' breathing zones using the National Institute for Occupational Safety and Health method. Noncancer and cancer risks due to the measured metals were calculated according to the United States Environmental Protection Agency procedures. The results indicated that the noncancer risks owing to occupational exposure to lead (Pb) and manganese were higher than the recommended value in most of the workstations. The estimated cancer risk of Pb was also higher than the allowable value. Moreover, the results of sensitivity analysis indicated that the concentration, inhalation rate, and exposure duration were the most influencing variables contributing to the calculated risks. It was thus concluded that the present control measures were not adequate and further improvements were required for reducing the exposure levels.

Risk assessment of occupational exposure to anesthesia Isoflurane in the hospital and veterinary settings

Despite the modern ventilation and waste anesthetic gas (WAG) scavenging systems, occupational exposure to common volatile anesthesia, isoflurane, can occur in the hospital and veterinary settings, but limited information exists on potential exposure and health risk of isoflurane. We assessed exposure dose rates and risks among clinicians and veterinary professionals from occupational exposure to isoflurane. Through a critical review of open literature (1965 to 2020), we summarized potential adverse effects and exposure scenarios of isoflurane among the professional groups, including anesthetists, nurses, operating room personnel, researchers, and/or veterinarians. Deterministic United States National Research Council/Environmental Protection Agency's risk assessment framework (hazard identification, dose-response relationship, exposure assessment and risk characterization) was used to compute inhalation Reference Doses (RfDs), Average Daily Doses (ADDs), and Hazard Quotient (HQ) values—an established measure of non-carcinogenic (systemic) risks—from exposure to isoflurane to workers in hospital and veterinary settings. We identified the central nervous system as the main target for isoflurane, and that isoflurane has dose-dependent effects on cardiac hemodynamics, can impair pulmonary functions and potentially cross the utero-placental barrier leading to congenital malformation in fetus. Based on the modelled RfDs (range 0.8003–7.55 mg/kg-day) and ADDs (range 0.071–1.9617 mg/kg-day), we estimated 56 different HQ values, of which 5 HQs were higher than 1 (range 1.099–2.4512) under high exposure scenarios. Our results suggest a significant non-carcinogenic risk from isoflurane exposures among workers in the occupational settings. The findings underscore the need to significantly minimize isoflurane release to protect workers' health in the hospital and veterinary environments.

Inhalation health risk assessment of occupational exposure to cypermethrin in farmers

ABSTRACT Exposure to cypermethrin is common and can lead to acute and chronic health effects. This study aimed to determine the quantitative inhalation risk ofcypermethrinamong the farmers. This cross-sectional study was conducted in nine areas of Shiraz, Iran. Sampling of the respiratory zone was performed by OSHA PV-2063 method using XAD-2 adsorbent andquestionnaire was used to collect the required demographic characteristics and occupational information. Finally, the inhalation risk assessment for exposure to cypermethrin was performed by the Environmental Protection Agency (EPA) method.The mean time-weighted average (TWA) and hazard quotients (HQ) ranged from 0.21 ± 0.1 to 1.68 ± 0.65 and 0.58 ± 0.11 to 1.68 ± 0.46, respectively. 55.6% and 15.2% of the tree spraying and field spraying of the exposed group had HQ more than 1, respectively. Investigation shows that there is no significant relationship between demographic characteristics and HQ values (except height). Exposure frequency (EF), TWA and exposure hour per day had the strongest relationship with HQ.This study showed that the kind of spraying is effective in the amount of risk exposure. The most focus to reduce the health effects associated with inhalation exposure to cypermethrin should be on lowering TWA and exposure hour per day.Due to the high risk of exposure in farmers, it is necessary to identify other effective factors by conducting further studies and presenting their related practical plans.

Quantitative and Semiquantitative Health Risk Assessment of Occupational Exposure to Styrene in a Petrochemical Industry

BackgroundStyrene is one of the aromatic compounds used in acetonitrile–butadiene–styrene (ABS) producing petrochemicals, which has an impact on health of workers. Therefore, this study aimed to investigate the health risks of styrene emitted from the petrochemical industry in Iran.MethodsAir samples were collected based on NIOSH 1501 method. The samples were analyzed by the Varian-cp3800 gas chromatograph. Finally, risk levels of styrene's health effects on employees were assessed by the quantitative method of the U.S. Environmental Protection Agency (U.S. EPA) and the semiquantitative way by the Singapore Occupational Safety and Health Association.ResultsBased on the results, the employees had the highest average exposure to styrene vapors (4.06) in the polybutadiene latex (PBL) unit. Therefore, the most top predictors of cancer and non-cancer risk were 2.3 and 7.26, respectively. Given that the lowest average exposure (1.5) was in the dryer unit, the prediction showed a moderate risk of cancer (0.8) and non-cancer (2.3) for the employees. The EPA method also predicted that there would be a definite cancer risk in 16% and a probable risk in 76% of exposures. However, according to the semiquantitative approach, the rate of risk was at the “low” level for all staff. The results showed that there was a significant difference (p < 0.05) between the units in exposure and health risk of styrene (p < 0.05).ConclusionGiven the high risk of styrene's health effects, appropriate control measures are required to reduce the exposure level.