Los disparos con armas de fuego, producen residuos de la combustión de los materiales energéticos empleados como propulsantes, así como metales pesados en partículas de diferentes tamaños. En el caso particular de la práctica de tiro que se desarrolla en polígonos cerrados, dependiendo de la eficiencia de los sistemas de ventilación, las dimensiones de la instalación, el número de disparos que se realizan, el tipo de munición y propulsante, el aire contiene diversos metales y componentes gaseosos que generan variados niveles de toxicidad.
Among the studied metals, Pb concentrations were highest; however, OSHA limit values were only exceeded in one case, when also the highest numbers of gun shots were made. The majority of Pb particles were in fractions >120 nm. Although concentrations of Cu, Ni, and Zn were significantly lower than Pb, they were more often present as nanoparticles (<120 nm). This increases their harmfulness, as nanoparticles can easily penetrate the cardiovascular and nervous systems. To decrease the potential health risks of heavy metals at shooting ranges, more efficient ventilation, optimization of the number of gunshots, and the use of lead‐free ammunition should be implemented.
1 Introduction
Small firearm shooting practice is regularly conducted at indoor shooting ranges. Depending on the efficiency of the ventilation, number of fired gunshots, ammunition type and propellant, and other factors, air can contain various metals, such as Cu, Pb, Zn, and Sb, and gaseous components such as CO, CO2, NO, NO, NH3, HCN, and CH4 1–9. Although lead‐free ammunition does not produce Pb, various metals (e. g. Cu, Zn, B, K, Fe), as well as organic compounds such as polyaromatic hydrocarbons and aldehydes, are present 8, 10, 11. Organic compounds in ammunition are found in the propellant powder and primer mixture. Inorganic compounds derive mostly from the primer mixture, case, and bullet 9. Altogether those energetic materials with metal fumes can be significant source of particles at shooting ranges 12.
Metals occur in ambient air as particulate matter (PM) in different size fractions and their health effects have been studied widely. PM has been associated with cardiovascular and respiratory morbidity and mortality due to both short‐ and long‐term exposure 13, 14. Many epidemiological studies have analysed the health effects of PM from traffic and residential heating 15. Few studies have investigated heavy metals at indoor shooting ranges in relation to potential adverse health effects and most focused on lead (Pb). They found lead‐containing ammunition can produce elevated levels of lead in the blood 16–21. Exposure to lead may produce several health symptoms, such as hypertension, hyper‐reflexia, tremors, and upper extremity weakness 22. People may also develop problems with cognition, memory, attention, language, and motor skills 23. It has also been shown that using lead‐free ammunition and/or more efficient ventilation can reduce exposure to lead 24.
Particulate matter (PM) differs in size and nano‐sized ultrafine particles (<100 nm) are considered most harmful, because of their high penetrability to the lungs 25, 26. When interacting with cells, PM nanoparticles can induce lipid peroxidation, cause intracellular oxidative stress, increase cytosolic calcium ion concentration, activate EGF receptors, and disrupt normal electron transport leading to oxidative stress 27. Metal oxide nanoparticles (MeONPs) have been known to cause cytotoxicity; the most harmful MeONPs are Tl2O/Tl2, Ag2O, and Au2O/Au2O3 [28]. When airborne metals at indoor shooting ranges 9 form oxides, the most toxic to human health could be PbO/PbO2, MgO, NiO, ZnO, and CuO 28. NiO is known to induce apoptosis by repressing SIRT1 29. Lung inflammation and cytotoxicity were observed in rats exposed to Cu2O3 30. ZnO nanoparticles cause cytotoxicity, apoptosis, cell cycle alternations, and genetic damage 31. One study revealed that CuO is more hazardous than PbO or ZnO, but because the heterogeneity of PbO suspensions does not allow (eco)toxicity assessments, its hazard score was low and it could actually be a higher risk 32. Thus, hazardousness seems to depend on the model and parameters used.
The aim of this study was to assess lead (Pb), copper (Cu), nickel (Ni), and zinc (Zn) concentrations in particulate matter at indoor military shooting ranges.
2 Experimental Section
2.1 Sample Collection
Measurements of particulate matter (PM) were done with ELPI+ (Electrical Low Pressure Impactor) (Dekati Ltd.). It classifies particles according to their aerodynamic diameter and enables real‐time measurement of particle size distribution and concentration in the size range 6 nm–10 μm. Particles that enter the impactor unit are separated using 14 different stages (filters) according to their aerodynamic size and behaviour. Particle samples were collected – over two hours – at three shooting ranges (SR) (Figure 1), and lead (Pb), copper (Cu), nickel (Ni), and zinc (Zn) concentrations analysed later in a laboratory. Background measurements were done at SR1 at night with no gunfire (Figure 2). In SR1 and SR2, samples were collected on two separate days; at SR3, measurements were conducted on a single day. During shooting training, Heckler & Koch USP (9×19 mm) pistols were used at SR1 and SR2, and Makarovs (9×18 mm) at SR3. Details of the ammunition are given in Table 1. Temperature, humidity, and air pressure were monitored during sample collection, and ventilation systems were working at normal settings.
The shooting ranges (photos are distorted for security purposes).
Particulate matter (PM) concentrations (μg/m3) in different fractions at the shooting ranges. A and B indicate different shooting days.
| Shooting range | Shooting day | Firearm type | Ammunition type | Number of gunshots |
|---|---|---|---|---|
| 1 | A | Heckler & Koch, 9×19 mm | m/39B, 6.75 g | 720 |
| 1 | B | Heckler & Koch, 9×19 mm | m/39B, 6.75 g | 480 |
| 2 | A | Heckler & Koch, 9×19 mm | Magtech Luger FMJ, 8 g | 510 |
| 2 | B | Heckler & Koch, 9×19 mm | Unknown | 270 |
| 3 | Makarov, 9×18 mm | Barnaul, 6 g | 875 |
2.2 Laboratory Methods
ELPI+ filters were analysed using an Agilent 7500 Series ICP‐MS instrument and Vista‐MPX CCD Simultaneous ICP‐OES (Agilent Technologies). The samples were dissolved in J.T. Baker nitric acid and diluted in Simplicity UV Millipore purified water. Internal Standard Stock Solution (100 mg/ml of Li, Sc, Ge, Rh, In, Tb, Lu, and Bi in 10 % HNO3) was used for IPC‐MS. ICP‐OS was calibrated using the Environmental Calibration Standard. Calibration graphs were made according to the Cot #QCCS‐26 “Quality Control Standard 26” solvent. Argon (Ar) gas was used for calibration.
Samples were dissolved from the filters using 5 ml concentrated nitric acid while being microwaved (1600 W, 200 °C, 3447.38 kPa, 10 minutes duration). The Teflon containers were left to cool‐down to room temperature. The solution was filtered through a paper filter into a 25 ml volumetric flask and filled with water to the mark.
Regarding the calibration charts, the squared correlation coefficient r2 of ICP‐OES was 0.99995 and ICP‐MS 0.9995. Spectral interferences were minimized and only less interfered isotopes were measured. Cu and Pb were measured with ICP‐OES, and Ni and Zn with ICP‐MS.
3 Results
Background particulate matter (PM) concentrations at shooting range 1 (SR1) were highest in fractions of 0.76 and 8.10 μm (coarse particle mode), and lowest in fraction 0.01 μm (Aitken mode). Average background PM concentration across fractions was 5.4 μg/m3 (maximum 10.5 μg/m3). Compared to concentrations during shooting, background levels were up to two orders of magnitude lower.
During shooting training at SR1, PM concentrations were highest on the first measurement day (A) when more shots were fired (Figure 2, Table 1). Among the fractions, the highest proportion of PM was 0.20 μm in diameter. On the second day (B), the 0.20 μm fraction remained highest, but differences between fractions 0.48–8.10 μm were non‐significant. Average PM concentration during shooting at SR1 on the first day (A) was 271.4 μg/m3(maximum 1161.4 μg/m3); the second day (B) average was 90.7 μg/m3 (maximum 126.4 μg/m3). At SR2, PM concentration was highest in fraction 0.31 μm on the first day (A) and 0.48 μm on the second day (B). On the first day (A), the average PM concentration was 19.6 μg/m3 (maximum 65.7 μg/m3) and on the second day 28.9 μg/m3 (maximum 151.9 μg/m3). At SR3, PM concentrations differed somewhat from SR1 and SR2, with coarser particles – PM in fractions of 1.22 μm and 1.94 μm – highest. The average concentration was 26.8 μg/m3(maximum 70.9 μg/m3).
Lead (Pb), Copper (Cu), Nickel (Ni), and Zinc (Zn) concentrations were analysed from ELPI+ impactor PM samples. The highest concentration of Pb was found at SR1 on the first day (A) and the lowest at SR3, with average concentrations of 54.3 and 6.1 μg/m3, respectively (Figure 3). Maximum concentration of Pb (150.0 μg/m3) was in the PM fraction 1.95 μm. Average concentration of Cu was highest at SR2 on the first day (2.7 μg/m3) and lowest at SR1 on the first day (0.8 μg/m3). Maximum concentration of Cu (4.0 μg/m3) was collected in the smallest analysed fraction (0.01 μm) at SR2 on the first day. Average concentration of Ni was highest at SR2 on the first day (0.3 μg/m3) and lowest at SR1 on the second day (0.1 μg/m3). Maximum concentration of Ni was 0.6 μg/m3 in the fraction 1.22 μm at SR1 on the first day. Average concentration of Zn was highest (0.7 μg/m3) at SR2 on the first day and lowest (0.3 μg/m3) at SR2 on the second day. Maximum concentration of Zn was 2.0 μg/m3 in the larger fraction 8.10 μg at SR2 on the first day.
Lead (Pb), copper (Cu), nickel (Ni), and zinc (Zn) concentrations (μg/m3) at the shooting ranges. A and B indicate different shooting days.
4 Discussion
In the current study, particulate matter (PM) concentrations and its proportions of lead (Pb), copper (Cu), nickel (Ni), and zinc (Zn) were analysed at indoor military shooting ranges during small firearms shooting training. As all ammunition contained Pb, high levels of lead in the air were expected. Earlier studies have shown that lead‐containing ammunition can result in high levels of lead in blood 33 and cause various health problems among shooters 19. To decrease these problems, ventilation settings should be set to get the most efficient air pollution removal possible, and lead‐free ammunition used. The higher number of gunshots fired at SR1 during the first day produced significantly higher levels of lead in the air.
Our analysis also showed gunfire produced in nano‐size fractions (<120 nm) more Ni, Cu, and Zn particles compared to Pb; though, lead had the highest concentrations in larger PM fractions. Among the shooting ranges, SR1 had most nano‐size particles produced during shootings, followed by SR2 on the second measurement day. In general, concentrations were highest at SR1 and lowest at SR3, despite the highest number of gunshots having been fired at the latter range. The main explanation of this counterintuitive result could be the different firearm and or ammunition used as well as differences in the ventilation.
The problem of high heavy metal levels military personnel can be exposed to has been noted before 20. Current knowledge is mostly limited to the toxicity of lead, because most ammunition contains it 16, 21, 34. According to Occupational Safety and Health Administration (OSHA) standards, employees should not be exposed to over 50 μg/m3 of airborne lead averaged over an eight hour period, and action must be taken if the concentration is 30 μg/m3 or more 35. Our study involved military personnel and their exposure time was two hours during our measurements. If we recalculate this on an eight hour basis, only at SR1 on one day were OSHA Pb standards exceeded.
We also found Ni, Cu, and Zn in significant concentrations, and the potential adverse health effects of exposure to these metals have been shown in vitro 28, 29, 36. Moreover, it has been noted that occupationally exposed people have a higher risk of respiratory tract cancer due to inhalation of nickel and copper 37. Recently, there has been an increase in the use of systemic serum amyloid A as a biomarker of inflammation in relation to exposure to zinc and especially copper‐containing metal fumes and particles 38. In study animals, exposure to occupational levels of air‐borne ZnO nanoparticles has resulted in inflammation of lung tissue, myocardial and DNA damage, and inflammation and apoptosis have been recognized 39.
This is the first large‐scale study conducted at multiple indoor military shooting ranges that has concentrated on nano‐sized particles. As the replacement of micrometer‐sized metal fuel powders in gas‐generating solid propellants with nanosized metal powders has become a common trend in the design of new types of propellants in recent decades, that could decrease the average size of the particles 40. As we did not change any indoor parameters during the measurements, and shooters used the same ammunition types as during normal training, our results reflect the situation on a usual shooting day. A limitation of the study could be that only four metals were analysed due to the very small concentrations in the smallest PM fractions, nor did we measure ventilation parameters. Our measurements at the different shooting ranges are not fully comparable, because of differences in the speed of air exchange, guns and ammunation. In addition, we could not influence the number of gunshots fired at each SR, or collect any information about the shooters due to security reasons.
Future studies should measure ventilation parameters, such as ventilation rates, and could analyse a larger number of compounds if a high enough number of shots are made. New studies could also compare different ammunition types, i. e. Pb‐containing to Pb‐free, and how their use could affect human health. Another important aspect could be biomonitoring of Ni, Cu, and Zn – to compliment the already widely implemented Pb biomonitoring – among personnel to study the health effects of heavy metals.
5 Conclusions
Among the studied metals, Pb concentrations were highest and on one day at shooting range 1 exceeded the standards set by the OSHA. More efficient ventilation, minimizing the number of gunshots, and the use of lead‐free ammunition could help to fulfil the OSHA requirements. Cu, Ni, and Zn were relatively more often present as nanoparticles (<120 nm), which increases the health risks.
Fuente: https://onlinelibrary.wiley.com
