Fine particulate matter (PM2.5) in a compost facility: heavy metal contaminations and health risk assessment, Tehran, Iran

Biomonitoring of metals in the blood and urine of waste recyclers from exposure to airborne fine particulate matter (PM2.5)

This is the first systematic investigation of occupational exposure to toxic metals among waste recyclers in municipal waste recycling facilities. Concentrations of heavy metals (HMs) in the blood and urine of exposed recyclers in different jobs were compared to control groups (administrative department), identifying possible work-related and socio-demographic exposure factors. The potential relationship between HMs levels in PM2.5 and HM concentrations in the blood and urine of recyclers was studied for ten elements. Mean concentrations of HMs of recyclers were significantly higher than for the control group. Over 50% of the waste recyclers had HM levels higher than the recommended limits. The study revealed that most of the waste recyclers engaged in a minimum of three tasks, posing a challenge in establishing a correlation between specific tasks and the levels of elements monitored through biomonitoring. Co levels in blood and Fe levels in the urine of waste recyclers have a significant relationship with the increase in daily working hours. Among the variables related to the participant's demographic information, the level of education and monthly income were significantly different compared to the control group. Also, a significant correlation was found between HM levels in PM2.5 personal exposure and recyclers' urine and blood. Management controls include workflow or, in other words, alternate relocation of workers exposed to severe risks. Engineering controls such as ventilation systems, applying appropriate personal protective equipment (PPE), and risk management methods are the implementation cases to reduce exposure.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40201-024-00924-y.

Health risk and toxicity assessment of exhaust air from non-incineration devices for hospital waste treatment in Tehran, Iran

this study investigates the health risks and cytotoxicity associated with volatile organic compounds (VOCs) emitted from non-incineration devices used in hospital waste management. The research focuses on the levels of BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) across four hospitals in Tehran, Iran, during the period from October 2022 to March 2023. BTEX concentrations were measured using Gas Chromatography (GC), and cytotoxicity was evaluated through the MTT assay on A549 cells.Results revealed that toluene was the most abundant BTEX compound, with concentrations ranging from 69.30 to 136.68 µg/m2, followed by m- and p-xylene. Benzene concentrations were notably lower, ranging from 7.32 to 34.80 µg/m2. Hazard quotient (HQ) assessments indicated a lower health risk in hospitals A and D, while hospitals B and C showed HQ values exceeding one, signifying higher potential risks. The study also demonstrated significant cytotoxicity across all hospital waste treatment devices, with the highest cytotoxicity observed in samples from autoclaves equipped with shredders, likely due to the presence of pharmaceutical waste.The findings highlight the necessity for stringent monitoring and regulation of VOC emissions from non-incineration devices to mitigate potential health risks, emphasizing the importance of effective waste management practices in healthcare facilities. This study contributes valuable insights for developing new policies and strategies to reduce the negative environmental and health impacts of hospital waste management.

Development of a comprehensive air risk index and its application to high spatial-temporal health risk assessment in a large industrial city

Particulate matter (PM) contains various hazardous air pollutants (HAPs) that can adversely affect human health, highlighting the need for an integrated index to represent the associated health risks. In response, this study developed a novel index, the comprehensive air-risk index (CARI), for Ulsan, the largest industrial city in South Korea. This index integrates toxicity-weighted concentrations of polycyclic aromatic hydrocarbons (PAHs) and heavy metals using their inhalation unit risks. CARI was categorized into four risk levels based on probabilistic health risks. Over eight years (2013-2020) in Ulsan, the risk from PAH exposure showed a decreasing trend, whereas the risk from heavy metals remained stable, reflecting different emission patterns and major source types. PAHs and heavy metals contributed 38.1% and 61.9% to CARI, respectively, highlighting the greater impact of heavy metals on human health. Unlike the monthly variations in PM2.5 concentrations, CARI values tended to increase in the summer and decrease in the spring and fall, indicating the impact of local emissions, particularly from petrochemical and non-ferrous industrial facilities. Moreover, a machine learning model enhanced the spatio-temporal resolution of CARI, showing that 'unhealthy' days were 2.4 times more frequent in industrial areas than in urban areas. In conclusion, CARI is a promising tool for assessing health risks in industrial cities and for developing risk-based management plans. Furthermore, we propose the development of a national-scale real-time CARI system by enhancing the spatio-temporal resolution of HAP data through the use of machine learning.

Pollution characteristics and health risk assessment of heavy metals in PM2.5 in Fuxin, China

Fuxin is located in the atmospheric channel around Bohai Bay, and its geographical location is very special. Few existing studies have investigated the pollution characteristics and health risk assessment of heavy metals in atmospheric PM2.5 during the four seasons in Fuxin, so a total of 180 PM2.5 samples were collected from four sampling sites in Fuxin from December 2021 to November 2022. The seasonal distribution characteristics of V, Cr, Mn, Co, Ni, Cu, Zn, Pb, As, Sb, Cd and Ba were analysed via inductively coupled plasma-mass spectrometry (ICP‒MS), and the source of the heavy metals was analysed via the enrichment factor (EF) and principal component analysis (PCA). A health risk model was used to assess the health risk of respiratory exposure in men, women and children in Fuxin. The results revealed that the annual average mass order of heavy metals in Fuxin PM2.5 was Zn (0.2947 μg·m-3) > Pb (0.0664 μg·m-3) > As (0.0225 μg·m-3) > Ba (0.0205 μg·m-3) > Mn (0.0187 μg·m-3) > Cu (0.0140 μg·m-3) > Cr (0.0095 μg·m-3) > V (0.0067 μg·m-3) > Ni (0.0061 μg·m-3) > Sb (0.0024 μg·m-3) > Cd (0.0019 μg·m-3) > Co (0.0007 μg·m-3). The annual average concentration of As was 3.75 times the GB3095-2012 (China) secondary standard limit, and the concentration of hazard quotient (HQ) in PM2.5 was lower than 1, but the concentration of incremental lifetime cancer risk (ILCR) in As was higher than the cancer risk threshold (10-4). These findings indicate a certain risk of cancer in the urban population of Fuxin. Therefore, it is necessary to control the emissions created from coal burning to minimize the health risks to the people of Fuxin.

Chemical Characterization and Assessment of Public Health Risk due to Inhalation of PM2.5 in the City of Salamanca, Guanajuato

In this study, we conducted an analysis of health risks faced by residents of Salamanca, Mexico, who were exposed to fine particulate matter with a diameter of 2.5 μm (PM2.5) through inhalation. The characterization and analysis of these particulate matter samples were undertaken. A total of 131 samples were collected from two different sites: 65 from the Red Cross site (RC) and 66 from the Integral Family Development site (DIF) in 2014-2015. These samples were analyzed for a set of chemical components, including metals and ions. Non-cancerous health risk levels associated with PM2.5 exposure through the human respiratory system, as per the WHO benchmark (assigned a value of 1), revealed notable risk values for two elements: Manganese (Mn) with a range of 1.19-2.12 in the adult population and 1.59-2.84 in the child population, and Nickel (Ni) with a uniform risk value of 1.39 for both evaluated population groups. However, concerns arose regarding potential non-cancerous effects as the cumulative risk levels for various assessed elements showed elevated indices. These ranged from 3.81 to 4.4 in adults and 4.48-5.24 in children. This study provided comprehensive data on composition and its potential impact on human health, offering valuable insights for the implementation of mitigation measures aimed at reducing inhalation-related exposure.

Size-classified aerosol-bound heavy metals and their effects on human health risks in industrial and remote areas in Japan

Airborne aerosols were collected in six size classes (PM<0.1, PM0.1-0.5, PM0.5-1, PM1-2.5, PM2.5-10 and PM>10) to investigate aerosol health risks in remote and industrial areas in Japan. We focused on heavy metals and their water-dispersed fractions. The average concentration of heavy metals was 18 ± 25-86 ± 48 ngm-3 for PM<0.1, 46 ± 19-154 ± 80 for PM0.5-1 ngm-3, 98 ± 49-422 ± 186 ngm-3 for PM1-2.5, 321 ± 305-1288 ± 727 ngm-3 for PM2.5-10 and 65 ± 52-914 ± 339 ngm-3 or PM>10, and these concentrations were higher in industrial areas. Heavy metals emitted from domestic anthropogenic sources were added to the long-range transport component of the aerosols. The water-dispersed fraction of heavy metals contained 3.3-40.1% of the total heavy metals in each size class. The relative contribution of Zn and other species (As, Cd, Cr, Ni, Pb, Mn, V and Cu) increased in the water-dispersed fraction. Smaller particles contained greater proportions of the water-dispersed heavy metal fraction. Carcinogenic risk (CR) and the hazard index (HI) were estimated for each size class. The CR of carcinogens was at acceptable levels (<1 ×10-6) for five particle size fractions. The HI values for carcinogens and noncarcinogens were also below acceptable levels (<1) for the same five size fractions. The estimated CR and HI values were dominated by contributions from the inhalation process.

Health risk assessment of heavy metals in exposed workers of municipal waste recycling facility in Iran

Exposure to heavy metals (HMs) present in the particulate matter from municipal solid waste during pretreatment and recycling processes may pose a serious health risk to workers. This was the first study on the exposure of municipal solid waste (MSW) recycling workers to toxic metals. The concentrations of HMs (Cd, Pb, As, Co, Cr, Ni, Cu, Fe, Mn, and Zn) during personal exposure to PM2.5 among municipal waste recycling facility workers in Kashan City, Iran, were investigated from January 15 to March 15, 2023. The research was performed in the three main stages of the waste recycling process: dismantling, sorting, and collecting. PM2.5 samples were collected using a personal environmental monitor (PEM) attached to a sampling pump. The non-carcinogenic and carcinogenic health risk values and related uncertainty for waste recyclers from HMs inhalational exposure were calculated using USEPA methodology and Monte Carlo simulations. The results showed that the dismantlers exhibited the highest exposure concentrations of PM2.5 (mean 2148 ± 1257 μg m-3), followed by sorters (mean 1864 ± 965 μg m-3), and collectors (mean 1782 ± 876 μg m-3). Health risk assessment indicated that 95th percentile contents of Ni, As, Co, and Zn were responsible for the non-carcinogenic risk (HQ) values exceeding the acceptable level of 1. The contents of As, Ni, and Cr in PM2.5 caused a non-acceptable carcinogenic risk for waste recyclers due to inhalational exposure, as the carcinogenic risk (CR) values exceeded the acceptable threshold of 1 × 10-6. Monte Carlo simulation results revealed that the mean and median CR values from inhalational exposure to carcinogenic HMs exceeded the acceptable level of 1 × 10-6 for municipal waste recyclers. As results of this study indicated the high-risk to hazardous metals for waste recyclers due to occupational exposure in the MSW recycling sites, it is suggested to consider workers' exposure as the public health concern.

Characteristics and health effects of particulate matter emitted from a waste sorting plant

Solid waste components can be recycled in waste paper and cardboard sorting plants (WPCSP) through a multistep process. This work collected 15 samples every six days from each of the 9 points selected to study the processes taking place in a WPCSP (135 particulate matter samples total). Examining the concentration and size fraction of particulate matter (i.e., PM₁, PM_2.5 and PM₁₀) in WPCSP is an essential issue to notify policy makers about the health impacts on exposed workers. The major activities for increasing of the concentration of PM in various processing units in the WPCSP, especially in hand-picking routes I and II were related to manual dismantling, mechanical grinding, mechanical agitation, and separation and movement of waste. The results of this work showed that a negative correlation between temperature and particulate matter size followed the order PM₁₀ > PM_2.5 > PM₁. Exposure to PM_2.5 and PM₁₀ in the WPCSP lead to possible risk (HI = 5.561 and LTCRs = 3.41 × 10^-6 to 9.43 × 10^-5 for PM_2.5 and HI = 7.454 for PM₁₀). The exposure duration and the previous concentrations had the most effect on the ILCRs and HQs for PM_2.5 and PM₁₀ in all sampling sites. Hence, because WPCSP are infected indoor environments (I/O ratio > 1), the use of control methods such as isolation of units, misting systems, blower systems equipped with bag houses, protective equipment, a mechanical ventilation system, and additional natural ventilation can reduce the amount of suspended PM, enhance worker safety, and increase the recycling rate.

Exploring sources and health risks of metals in Beijing PM2.5: Insights from long-term online measurements

To gain a comprehensive understanding of sources, health risks, and regional transport of PM_2.5-bound metals in Beijing, one-year continuous measurement (K, Fe, Ca, Zn, Pb, Mn, Ba, Cu, As, Se, Cr, and Ni) was conducted from December 2016 to November 2017 and Positive Matrix Factorization analysis (PMF) was applied for source apportionment. It was found that the seasonal variation of sources could vary significantly among metals. Sources of Ca, Ba, As, Se, and Cr did not show much seasonal variations, with the contribution of its predominant source higher than 35% in each season. However, the major sources of K, Fe, Zn, Pb, Mn, Cu, and Ni exhibited obvious seasonal variations. In addition, the characteristics of metals in haze episodes were comprehensively investigated. Haze episodes in Beijing were characterized by higher metal concentrations and health risks, which were about 2- 6 times higher than non-haze periods. Moreover, the types of haze episode were different in winter and spring. Haze episodes in winter were mostly influenced by coal combustion, the contribution of which increased greatly and accounted for about 30% of PM_2.5. The metals such as K, Zn, Pb, As, and Se significantly increased, which were mainly transported from south of Beijing. During haze episodes in spring, dust was an important source, which contributed to higher concentrations of crustal metals that transported from northwest of Beijing. To quickly and effectively identify source regions of metals in Beijing during haze episodes, a new diagnostic ratio method using Ca as a reference was developed. The ratios of some anthropogenic metals to Ca significantly increased when air mass was mainly from south of Beijing during haze episodes while the ratios remained constantly low in non-haze periods, when local emissions dominated. This method could be useful for rapid identification and control of metal pollution in Beijing.

Human health risk assessment for toxic elements in the extreme ambient dust conditions observed in Sistan, Iran

This study evaluates the bioaccessibility and health risks related to heavy metals (Cd, Cr, Co, Cu, Mn, Ni, Pb, Zn and metalloid As) in airborne dust samples (TSP and PM_2.5) in Zabol, Iran during the summer dust period, when peak concentration levels of PM are typically observed. High bioaccessibilities of carcinogenic metals in PM_2.5 (i.e. 53.3%, 48.6% and 47.6% for Ni, Cr and As, respectively) were calculated. The carcinogenic and non-carcinogenic health risks were assessed for three exposure pathways (inhalation, ingestion and dermal contact), separately for children and adults. Non-carcinogenic inhalation risks were very high (Hazard Index: HI > 1) both for children and adults, while the carcinogenic risks were above the upper acceptable threshold of 10^-4 for adults and marginally close (5.0-8.4 × 10^-5) for children. High carcinogenic risks (>10^-4) were found for the ingestion pathway both for children and adults, while HI values > 1 (8.2) were estimated for children. Carcinogenic and non-carcinogenic risk estimates for dermal contact were also above the limits considered acceptable, except for the carcinogenic risk for children (7.6 × 10^-5). Higher non-carcinogenic and carcinogenic risks (integrated for all elements) were associated with the inhalation pathway in adults and children with the exception of carcinogenic risk for children, where the ingestion route remains the most important, while As was linked with the highest risks for nearly all exposure pathways. A comparative evaluation shows that health risks related with toxic elements in airborne particles in Sistan are among the highest reported in the world.

Assessment of airborne particles and bioaerosols concentrations in a waste recycling environment in Brazil

This study aims to assess the concentrations of size-fractioned particle mass (PM_1.0, PM_2.5, PM_4.0, PM₁₀) and number (PNC_0.3, PNC_0.5, PNC_1.0, PNC_2.5), bacteria, and fungi in a Materials Recycling Facility (MRF) in Brazil. The measurements were performed inside the waste processing shed (P1) and in the outdoor environment (P2) during working days in winter and spring of 2017, and summer of 2019. A total of 2,400 min of PM, 1,440 min of PNC, and 216 samples of bioaerosols were collected in the morning and afternoon. P1 has the strongest air contamination with mean values of 475.5 ± 563.7 µg m⁻³ for PM₁₀, 58.6 ± 36.0 cm⁻³ for PNC_0.3, 1,088.8 ± 825.2 colony-forming units per cubic meter (CFU m⁻³) for bacteria, and 2,738.3 ± 1,381.3 CFU m⁻³ for fungi. The indoor/outdoor ratios indicated the large influence of indoor sources due to the activities performed inside P1 that promote the generation and resuspension of pollutants. Gram-positive bacteria dominated with 58.6% of indoor samples. Overall, our results show a critical indoor air quality situation in a Brazilian MRF, which may cause several health risks for waste pickers. Finally, we call attention to the lack of occupational exposure limits for bioaerosols in industrial workplaces and mainly in MRFs.

Source identification and pollution degree of deposited dust on green space in Tehran

The information about concentration, sources, and pollution degree of heavy metals belong to deposited dust (DS) can be used for decision-making in air quality control, removal role of green space, and urban forest management. The objectives of the study were to identify and evaluate DS pollution degree with the introduction of a new index. DS samples were collected from five tree species. The concentration of heavy metals and pollution degree of DS were evaluated by enrichment factors (EF), geoaccumulation index (I_geo), modified degrees of contamination (mC_d), and a new comprehensive index as weighted degree of contamination factor (wC_d). The values of EF showed that all samples were significant to extremely high enrichment and DS samples were emitted from anthropogenic activities. I_geo values indicated that DS samples were polluted by Cd (80-97%) and Pb (100%). In addition, mC_d results showed more than 67% of samples were unpolluted. There was a clear fact that I_geo results showed high pollution levels for Pb, Cd, and low for Ni, and the mCd results were incompatible with them. When all heavy metals were used without their importance to mC_d, calculation can cause bias from reality. For this reason, the new index was suggested as wC_d for all heavy metals that its results showed high to very high degree of pollution and that it was compatible with other indices results.

A follow-up study on the characterization and health risk assessment of heavy metals in ambient air particles emitted from a municipal waste incinerator in Zhejiang, China

To confirm our hypothesis that inhalation might be the primary exposure route of heavy metals for children living in proximity to a municipal waste incinerator (MWI), we conducted a one-year follow up study to characterize the distributions of heavy metals featured in different types of ambient air particles, including PM₁, PM_2.5 and PM₁₀, at two exposure sites near the MWI (E1 and E2) and one control site (C) in Zhejiang, China. Particle samples were collected by a mid-volume sampler and heavy metals were determined by the inductively coupled plasma mass spectrometry method. The mass concentrations of PM₁, PM_2.5 and PM₁₀ were 52.0, 85.8 and 100.3 μg/m³ at E1 site, while the concentrations were 40.2, 92.1 and 106.6 μg/m³ at E2 site and 33.4, 55.6 and 66.1 μg/m³ at C site, respectively. Both E1 and E2 had higher PM₁, PM_2.5 and PM₁₀ levels than C site. The levels of pollution were season dependent, with autumn having the highest levels of PM₁, PM_2.5 and PM₁₀ across all three sampling sites. Regarding the distributions of heavy metals, Pb accounted for the majority of the seven metals in all groups, ranging from 43.2% to 51.3%, followed by Mn that ranged from 22.0% to 32.0%. The Pb levels of PM₁, PM_2.5 and PM₁₀ in the MWI area were 22.6, 34.2 and 36.2 ng/m³, respectively, while Mn levels were 10.1, 20.0 and 23.5 ng/m³, respectively. The health risk assessment results suggested that residents were suffering high non-carcinogenic risk posed by MWI-emitted particle-bound toxic metals, as well as the high lifetime carcinogenic risk. This study revealed that ambient air, no matter whether near or far away from an MWI, bore more PM₁, PM_2.5 and PM₁₀ particles than general, non-polluted ambient air, especially in autumn.

Concentration, sources and human health risk of heavy metals and polycyclic aromatic hydrocarbons bound PM2.5 ambient air, Tehran, Iran

The exposure to heavy metals and polycyclic aromatic hydrocarbons (PAHs) bound to particulate matter 2.5 (PM_2.5) ambient air can result in some adverse health effect. In the current study, PM_2.5 ambient air of Tehran metropolitan, Iran, was characterized by the aid of scanning electron microscope and energy-dispersive X-ray techniques. Also, the human health risk of heavy metals and PAHs bound PM_2.5 for adults and children was assessed using the Monte Carlo simulation method. According to our findings, a size range of 0.97-2.46 μm with an average diameter of 1.56 μm for PM_2.5 was noted. The average concentration of PM_2.5 in ambient air (8.29E+04 ± 2.94E+04 ng m^-3) significantly (p < 0.05) was suppressed the national (2.50E+04 ng m^-3), World Health Organization (2.50E+04 ng m^-3) and Environmental Protection Agency (3.50E+04 ng m^-3) standard limits. The rank order of heavy metals bound PM_2.5 was determined as Al > Cu > Cd > Cr > Pb > Ni > Fe > Mn. The maximum concentration among 16 PAHs compounds investigated was correlated with Phenanthrene. Considering the principal component analysis, the main source of heavy metals (Ni, Pb and Cr) is vehicle combustion. Moreover, the rank order of exposure pathways based on their health risk was ingestion > inhalation > dermal contact. Moreover, the significant health risks for Tehran residents due to heavy metals bound PM_2.5 [target hazard quotient > 1; carcinogenic risk > 1.00E-06)] were noted based on the health risk assessment. Excessive carcinogenic risk (ECR) of PAHs bound PM_2.5 was 4.16E-07 that demonstrated that there is no considerable risk (ECR < 1.00E-06).

High-temperature chlorination of PbO and CdO induced by interaction with NaCl and Si/Al matrix

Municipal solid-waste incineration leads to emission of lead (Pb) and cadmium (Cd), which vaporize in furnace and condense in flue. NaCl in waste has been proven to enhance volatilization of Pb and Cd at high temperatures via chlorination of oxides to chlorides; however, this process was not well-understood so far due to its complexity. This study decoupled the indirect chlorination process and direct chlorination process so that these two processes were investigated separately. A horizontal tube furnace was used to heat the mixtures of NaCl and Si/Al matrix for indirect chlorination and the mixtures of NaCl, PbO/CdO and Si/Al matrix for direct chlorination. A set of dynamic sampling devices was designed and used to obtain dynamic data during temperature rising. The indirect chlorination process was initiated above 800 °C in O₂ + H₂O atmosphere and O₂ atmosphere and above 1000 °C in N₂ atmosphere. Al₂O₃ exhibited higher activity than SiO₂ to react with NaCl, releasing HCl or Cl₂. In the Cl release reaction, NaCl was in the gas phase. The direct chlorination process was initiated at 650–700 °C when the Si/Al matrix contained SiO₂ only and at around 800 °C when the Si/Al matrix contained Al₂O₃ only or both SiO₂ and Al₂O₃. SiO₂ exhibited higher activity than Al₂O₃ in direct chlorination. The pre-reaction between PbO/CdO and Si/Al matrices was considered as the necessary condition for direct chlorination. During chlorination in O₂ + H₂O atmosphere, indirect chlorination and direct chlorination occurred simultaneously, and the latter dominated the volatilization of Pb and Cd.

The chlorination process by NaCl was decoupled as indirect chlorination and direct chlorination, which were investigated separately.