EVALUATION OF EXPOSURE TO AIRBORNE HEAVY METALS AT GUN SHOOTING RANGES
It is well known that the environment of shooting ranges and their near surroundings is contaminated by lead and other heavy metals. Soil contaminated by lead represents a serious danger due to weathering reactions of Pb bullets and fine lead particles. Some organizations and authorities have issued recommendations to protect safety and health of persons employed at shooting ranges. A crucial issue is reproducible and reliable size dependent sampling of fine and ultrafine aerosols for observation by scanning electron microscopy (SEM) and chemical analysis.
Aerosols formed during shooting events were studied with various techniques including the wide range size resolving sampling system, Aero Select, followed by inductively coupled plasma mass spectrometry chemical analysis, scanning electron microscopy, and fast mobility particle sizing. The total lead mass aerosol concentration ranged from 2.2 to 72 μg m−3. It was shown that the mass concentration of the most toxic compound lead is much lower than the total mass concentration.
Measurement and Sampling:
Samplings and measurements were done in two places: an indoor shooting range (ISR) and an open air shooting range (OSR). Two types of ammunition were tested, classic ammunition [TOX], and so called ‘green’ ammunition [NON-TOX]. Samples were collected by the Aero Select, under varied conditions, with sessions performed in different locations, always using the same weapon (Luger, 9 mm). Lead containing primer ammunition [TOX] was used both outdoors and indoors while a ‘green’ ammunition [NON-TOX], where the lead is replaced by other metals and substances, was only used indoors (with ventilation). For the evaluation of the health risk related to nanoparticles, the mass concentrations of lead, manganese, antimony, and boron were measured.
Results and Discussion of the Size Distribution and Toxicity:
The diagram (Fig. 1) shows the spatial arrangement of both the OSR and ISR along with the positions of the sampling and measurement equipment. In the case of the ISR the equipment was immediately behind the people firing. In the open air shooting range the equipment was situated approximately 3 m behind the firing staff.
The total aerosol mass concentration of lead in the indoor environment was 72 μg m−3 and in the OSR was 10 μg m−3. These levels of lead are much higher than the background concentration taken in the open air (0.21 μg m−3). Some 30–50% of these inhaled particles are retained in the respiratory system and all of this retained lead is absorbed into the body. All lead particles that are cleared by the lung can be swallowed and result in further lead absorption from the gastrointestinal tract. The particular chemical form of lead is not considered an important factor for respiratory absorption. The background mass distribution of lead was taken in the Ostrava-Radvanice district which is known as a heavy polluted area of an industrial town. Nevertheless, the concentrations of lead at shooting ranges are still much higher than the background concentration measured in this polluted industrial area.
Summary statistics for the total concentration of particles are reported in Table 1. It is evident that in the case of OSR very sharp peaks arising during firings do not significantly affect the median. The background reading in this case even shows a higher median due to how short the firing bursts are compared to the total measurement time. By comparison, the firings have a more significant impact in the ISR environment. The median values are at least one order of magnitude higher than the background reading. This suggests that despite the ventilation, particles are still better contained within the ISR than in the case of the OSR. Therefore, the total concentration of aerosols in the shooting ranges was typical of a polluted area.
|Type of measuring stage:||MED (cm−3)||MAD||GM (cm−3)||GSD||Maximum (cm−3)|
|OSR TOX, shooting period (b)||1.88E+04||7.50E+03||2.67E+04||2.75||3.64E+06|
|OSR, background (b)||2.71E+04||1.70E+03||2.72E+04||1.10||3.66E+04|
|OSR TOX, shooting period (c)||2.63E+04||4.10E+03||3.92E+04||2.68||6.07E+06|
|OSR, background (c)||2.62E+04||5.00E+02||2.63E+04||1.03||3.04E+04|
|ISR NON-TOX, shooting period||3.56E+05||2.66E+05||3.79E+05||3.83||1.78E+07|
|ISR NON-TOX, background||6.43E+03||3.20E+02||6.47E+03||1.08||9.54E+03|
|ISR TOX, shooting period||7.98E+04||5.65E+04||1.01E+05||4.60||4.51E+06|
|ISR TOX, background||5.85E+03||6.85E+02||5.83E+03||1.15||7.82E+03|
Table 1. Summary of airborne exposures. MAD, median absolute deviation; MAX, maximum measured value; MED, median; GM, geometric mean; GSD, geometric standard deviation. (a) The background level was measured just before shooting started. All statistical calculations are based on total concentration data from FMPS with 1s averaging interval. (b) Measured 15 June 2011. (c) Measured 29 June 2011.
Aerosols formed during shooting events have been studied with various techniques including the wide range sampling system Aero Select and an FMPS. Mass size distributions from the Aero Select and number size distributions from the FMPS were compared and both methods were found to be consistent with each other. The airborne lead mass concentration was in the range from 2.2 to 72 μg m−3. It is shown that the mass concentration of the most toxic compound, lead, is much lower than the total mass concentration. This highlights the need for chemical analysis of aerosol particles in health risk evaluation.
A very important finding of this study is the confirmation of the occurrence of high nanoparticle concentrations which represent an increased risk of penetration into the human body. There was a confirmed significant lowering of concentrations of lead and other toxic metals like antimony in the atmosphere of ISRs using ‘green’ ammunition. On the other hand, higher concentrations of manganese and boron were measured. These metals might be the constituents of new types of primers and are occurring predominantly in the nano-range. Thus it was not confirmed that this new type of ammunition does not pose any health risk, rather it minimizes it in comparison to conventional ammunition.
Karel Lach, Brian Steer, Boris Gorbunov, Vladimír Mička and Robert B. Muir. Evaluation of Exposure to Airborne Heavy Metals at Gun Shooting Ranges. Ann. Occup. Hyg., (2014), 1–17 doi:10.1093/annhyg/meu097