hamze sharifi

During military operations, residual metals and weapons residue, including lead, copper, depleted uranium (DU), zinc, nickel, chromium, cadmium, etc., are released into the environment. These activities can result in human exposure to metal by inhalation or ingestion of released particles, as well as injury from embedded fragments. This study was conducted to investigate potential sources of metal emissions during military operations, pathways of metal exposure, and associated health risks.

This study is a review study conducted in the spring of 2023 by searching the PubMed, Web of Science, and Scopus databases and searching using the Google Scholar search engine using the keywords "Health effects", "health", "Metal", "Embedded Pieces", "Weapon" "Military" and related articles were selected and reviewed.

Residues of war weapons can directly cause exposure and contamination of plants, animals, and humans with metals through soil, air, underground, and surface water. Biomonitoring studies have shown an increase in the accumulation of these metals in plants, vertebrates and invertebrates. Exposure to these metals leads to adverse cardiovascular, neurological, etc. consequences in military personnel and negative consequences for the development of the nervous system in children living in military areas. Also, experimental studies in vivo and in vitro have shown the toxic effects of specific metals as well as widely used metal alloys.

Evidence shows that exposure to metals during military activities can be associated with metal toxicity and contribute significantly to adverse health effects. An increased metal load in the body may lead to latent and long-term effects in exposed people. The major effects of toxicity depend on various factors such as the type of weapon, chemical composition, routes of exposure, and environmental characteristics, which are currently poorly understood. Therefore, further studies in biological, epidemiological, and laboratory surveillance are needed to better characterize metal exposure associated with military operations.

Microplastics (MPs) are nowadays found in the air and in various terrestrial and aquatic environments and have become emerging pollutants. These particles can absorb other chemicals and microbial contaminants and release them into the environment and food chain. Despite the high efficiency of wastewater treatment plants (WWTPs) in removing MPs, WWTPs are still one of the major sources of MPs discharge to the environment. This study was conducted to evaluate the efficiency of MPs removal in a municipal WWTP with conventional activated sludge in Iran.

MPs particles were counted using a stereomicroscope after the initial preparation steps (sieving, chemical digestion with the catalytic wet peroxidation-oxidation and density separation with NaCl) and then analyzed for particle composition using a Raman micro-spectrometer.

MPs concentration in the influent, grit chamber, primary sedimentation tank, and effluent were 843.2 ± 147.5, 315.5 ± 54.7, 80.2 ± 19.1, and 11.13 ± 3.14 items/L, respectively. The overall MPs removal efficiency of the WWTP was 98.7%, with the grit chamber, primary sedimentation tank, and secondary sedimentation tank removed 62.6%, 27.9%, and 8.2% of the total MPs, respectively. The most abundant polymers were polypropylene (PP) and polyethylene (PE).

Despite the effective removal of MPs in WWTP, on average 4.47 × 1011 ± 1.03 × 1011 MPs are discharged into the receiving waters through the effluent of this WWTP annually. This means that WWTPs can be one of the major sources of MPs in the environment and efforts should be made to increase the efficiency of WWTPs and equip them with advanced technologies.

Recently, microplastics (MPs) have been found in the aquatic and terrestrial environments, air, and food. Other pollutants can be transported by MPs and pose a threat to the human, animal, and environment. Measurement and evaluation of microplastics can either increase knowledge about them or boost understanding of their possible harmful effects. However, no standard method has been established to measure microplastics and the measurement of microplastics has been done by various methods in different published studies. The aim of current study was to investigate different methods of measuring microplastics in water and wastewater environment and identifying the strengths and weaknesses of these methods.

The present review study was conducted during the winter 2021, by searching the papers cited in PubMed, Google Scholar, Web of Science, and Scopus databases using the keywords "Microplastic", "Water", "Drinking-water", "Wastewater", "Surface", "Bottled-water" and "Marine" and selecting articles published between 2015 and 2021 in reputable journals.

The main stages of MPs measuring in various studies included sampling and sieving, pretreatment and digestion, density separation, counting and Identification of MPs by their chemical composition.

Digestion using H2O2, density separation using NaCl, counting by stereomicroscope, and Spectroscopy using FTIR and micro-RAMAN are the most widely used methods in the studies related to detecting MPs in water and wastewater environment. However, different methods of measuring and identifying microplastics have made comparing the results of studies difficult and it seems that efforts should be made to standardize these methods.

 In this study, the microplastic (MP) concentration in several brands of salts was investigated. 

 Fifteen samples of crystallized salt, refined sea salt, unrefined sea salt, and rock salt were purchased from local markets and analyzed for MPs concentration. The salts were digested with the Catalytic Wet Peroxide Oxidation method first, and the MPs were floated based on density difference. Then, MPs were counted by scanning electron microscopy and nature was confirmed by using micro-Raman spectroscopy. 

 The MP concentrations in crystallized salt, refined sea salt, unrefined sea salt, and rock salt were 151.4 ± 48.8, 406.7 ± 93.3, 1417.4 ± 203.3, and 283.4 ± 97.0 MPs/kg, respectively. The most abundant polymers were polyethylene, polypropylene, and polyethylene terephthalate. The fiber was the dominant shape of MPs in all salt samples. 

 This study reveals the presence of MPs in crystallized salt, refined sea salt, unrefined sea salt, and rock salt. Therefore, the consumption of salts can expose humans to MPs.