Lead
Contamination from Shooting Sports
Performed
by Dean Moore
Chemistry
4181, University of Colorado, Spring 2004
Experiment
performed April 3 through April 9, 2004
Most
gun ammunition is made of lead or lead alloys, and the purpose of this research
was to determine levels of lead contamination resulting from shooting sports.
The paper uses terminology pertaining to guns without definition; see [1], [2]
and [3] for explanations. Flame atomic absorbance spectroscopy at 283.3 nm was
used to determine the lead content of samples. After the right-handed firing of
about fifty rounds of .38 Special half-jacketed ammunition from a Smith &
Wesson double-action .357 magnum revolver at a Boulder-area indoor range, for a
single right-hand sample, 880±119 mg of lead was found on the
right hand; assuming a hand area of exactly 12 square inches and scaling to a
square foot, this corresponds to 10600±1430 mg of lead per square foot. The
left hand yielded 443±152 mg of lead; this scales to 5320±1820 mg
of lead per square foot. Wall and soil samples varied widely, and the standard
deviation of the average was calculated by using the largest RSD of all samples
and the average. Two samples were taken from the wall of the same indoor
Boulder-area target range as the hand samples, and yielded an average of
16700±1620 mg of lead per square foot. Of soil samples, five samples
from the middle of an outdoor Boulder county trap range gave negative values,
and are taken as indeterminate. Two
samples taken by the firing line of a Boulder county trap range gave meaningful
numbers of high standard deviation and an average of 239±215 ppm. Six soil
samples taken from the impact zone of an outdoor target range in Boulder county
had values ranging from 57800 ±11400 ppm of lead to 106000±20600 ppm of lead,
and an average of 84600±16670 ppm lead was derived. No conclusions may be drawn
of wall and hand samples, as there were too few data points. It may be
concluded that soil lead concentrations far above EPA limits were found for the
impact zone of the Boulder-area target range, but it may have been a
concentrated sample and more investigation is needed.
The
objective of this research was to measure the lead contamination from shooting
sports by using flame atomic absorbance spectroscopy. Two types of samples were analyzed: soil
samples from outdoor target ranges, and swipes from hands used in shooting and
swipes from walls.
Lead is toxic to
nearly all life, and has been part of the environment for thousands of years
([4]); it is mentioned in the Book of Exodus (15:10)
in the Old Testament. LeadÕs toxicity is well-documented [5]; it has been implicated
in reducing IQ scores of children, in kidney disease,
high blood pressure, anemia, and many forms of damage to the reproductive
systems of both sexes, including impotence, miscarriage, and stillbirth [6].
Lead is and has been introduced to the environment in many
ways: from discarded lead-acid batteries, from the computer industry, from
power plants, leaded gasoline (banned in the United States since 1986, [7]),
natural sources, and others, including target shooting. Shooting ranges are
almost entirely unregulated, and the EPA does not consider the firing of
bullets and/or shot to be ÒdiscardingÓ lead, hence the EPA does not regulate
shooting sports [8]. A
Colorado study [9] found that after a three-month period of firearms
instruction at an indoor range, some police trainees had blood lead levels
above OSHA limits. Lead slowly oxidizes [10] when exposed to air, and
dissolves in acid water or soil, polluting soil and groundwater. It has been
estimated [11] that in soil of pH 5.5 that a shotgun pellet will dissolve
completely in 100-300 years.
Shooting
contributes lead to the environment in two ways: bullets and shot, and also primers,
which are often made with lead styphnate
[12].
Shooters may inhale lead, and lead may be absorbed through pores on the skin [13]. Spent ammunition and lead from primers may affect humans, and may kill birds including waterfowl [14] that mistake shotgun pellets for seeds, and predator/scavengers such as eagles [15], [16].
Outdoor
shooting sportsÕ contribution of lead to the environment is highlighted in the
next graph [17]:
Figure 1: Outdoor target ranges put more lead into the environment than nearly any other major industrial sector in the U.S., yet they remain almost entirely unregulated.
Published
EPA levels [5] of lead follow:
Table 1: EPA lead limits
Floors |
40 mg
of lead in dust / square foot |
Interior window sills |
250 mg
lead / square foot |
Bare soil in children's play areas |
400 parts per million (ppm) of
lead |
Bare soil in the rest of the yard |
1200 ppm average |
Flame
atomic absorbance spectroscopy was used due the methodÕs simplicity,
familiarity, and lead's strong response to the technique; leadÕs strong line at
283.3 nm was used.
This
research was adapted from the Lead in
Soil experiment [4]. Target
ranges from which samples were taken are not identified by name.
Lab Procedure: Due
to the use of concentrated acid, safety measures were taken. Gloves and lab
glasses were used throughout, and waste was properly disposed of. Water used
was 18 MW, and all
glassware was rinsed with 1% nitric acid before use.
Standard Preparation: A stock solution
of 103±0.631 ppm lead was
prepared by dissolving 0.0165±0.0001 g of lead nitrate to the mark in a 100 mL
volumetric flask with 1% nitric acid. Eight dilutions in 50 mL volumetric
flasks were prepared by adding 1% nitric acid to stock solution: 0.516±0.021
ppm, 1.03±0.022 ppm, 2.06±0.024 ppm, 5.16±0.061 ppm, 10.3 ±0.076 ppm,
25.8±0.180 ppm, 51.6±0.330 ppm, and 103±0.631 ppm of lead, the last being
undiluted stock solution.
Sample Gathering: Soil
samples were collected in sandwich bags from outdoor target ranges. Surface
samples of walls were collected by taking a picture frame, holding it on the
wall, and swiping the area with a baby wipe [18]. Hand swipes were taken in the
bathroom immediately after shooting, putting a lab glove on one hand, and
swiping the other with a baby wipe. A new glove was put on for the other hand,
storing both in plastic sandwich bags.
Samples Ran: These consisted of one
swipe from the right hand after the right-handed firing of about 50 rounds of
.38 Special half-jacketed ammunition from a Smith & Wesson .357 magnum
double-action revolver at an indoor range, one from the left hand. Unfortunately,
in the rush the type of ammunition was not collected. Two swipes were taken
perhaps a foot apart from the wall by the firing line of the same range; the
range obviously had poor ventilation and had dirty walls. Five samples of soil
were ran from the middle of a Boulder-area outdoor trap range, and three
samples were taken from by the firing line of the same Boulder-area trap range;
the area has been a trap range for Òover forty yearsÓ according to a bystander.
Six samples were ran from soil taken where bullets and shot impact the side
hill at a Boulder-area outdoor range; one of the previous six samples was found
to have two shotgun pellets in it, and the area has been a target range Òa long
time,Ó according to a University of Colorado student familiar with the area.
Sample
Preparation Samples were prepared in two ways, due to the use of both
soil samples from outdoor ranges and baby wipes for surfaces in indoor ranges:
soil samples were first ground with a mortar and pestle, and weighed to close
to 0.5 g. Both soil samples and baby wipes were placed in 100 mL beakers and
digested in 20 mL of concentrated nitric acid, and were heated on a hot plate
for an hour, swirling with a glass rod at the midpoint. The samples were cooled
in an ice bath and filtered into 100 mL volumetric flasks through Whatman-41
filter paper. The filter paper was washed with 18 MW water, and the volumetric flask was diluted to the mark
with 1% nitric acid. A soil blank was prepared with about 0.5 g of Ottawa sand,
and given the same treatment as other soil samples. The soil spike was prepared
by adding 5 mL of lead stock to ~0.5 g of Ottawa sand. A baby wipe blank was
prepared with an unused baby wipe; a baby wipe blank spike was prepared as the
soil blank spike, minus the weighing. Samples were slowly collected over
several days, and calibration standards and samples were all read the same
afternoon so as to have only one calibration curve.
Atomic Absorbance: Standards and samples
were measured on the University of ColoradoÕs Thermo Jarrell Ash Video 12
Spectrophotometer at 283.3 nm using a lead hallow cathode lamp and a bandwidth
of 0.5 nm. The standards were measured, and dynamic linear range was determined
to be from 0.516 to 51.6 ppm lead. All samples were then measured, and several
samples were diluted with 1% nitric acid to bring them into dynamic linear
range, and read a second time.
All calculations were done on Excel, at
95% confidence where applicable.
Lead
Calibration Curve: The dynamic linear range of the eight standards was 0.516 to 51.6 ppm lead; the highest concentration of 103 ppm, that
of the stock solution, was not used, as the correlation coefficient dropped
dramatically when it was included. Denoting absorbance A and concentration C,
the calibration curve was
A = (5920 ± 160)(mL/g)C +
(0.008±0.004) (unitless)
See Figure 2. The correlation coefficient was r = 0.998. The concentration error bars were nearly invisible. Of
note, the intercept was large.
Limit
of Detection: This was
problematic, owing to the calibration curveÕs large intercept, and the blankÕs
absorbance had a standard deviation of zero. The calibration standardÕs
absorbance reading at 0.516 ppm lead yielded negative lead concentration, while
that at 1.03 ppm yielded positive lead concentration, and 1.03 ppm lead may be
taken as a realistic limit of detection.
Calculations of
Extraction Efficiencies: For baby wipes, this
came in at 69.7±0.056%,
and for soil samples, it was 66.4±0.126%.
Calculations of Lead
Concentrations: Refer to tables 2 and 3
below for results. Note results are divided into areas and soil samples,
and it is important not to compare the two. For Lead per Square Foot calculations of hands, a hand area of exactly
12 square inches is assumed. Note Lead in
Grams is meaningless for wall samples. The two wall readings varied by a
factor of about 1.79, and the standard deviation was derived by using the
largest RSD of samples and average. For soil samples, results varied widely,
and low, high, and average values are given; standard deviations are calculated
by using the largest RSD of all samples and the average. See also Figure 1
above for EPA lead limits.
Table 2: Areas
Sample |
Lead in
Grams |
Lead per
Square Foot |
Right hand, one sample |
880 ± 119 mg of lead |
10600 ± 1430 mg
/sq. ft |
Left hand, one sample |
443 ± 152 mg of lead |
5320 ± 1823 mg
of lead/ sq. ft |
Indoor range walls, two samples |
-- |
16700±1620 mg of lead/ sq. ft |
Table 3: Soil Samples
Sample |
Lead
concentrations in ppm, low value |
Lead
concentrations in ppm, high value |
Average |
Middle of outdoor Boulder-area
trap range, five samples |
Negative |
Negative |
Meaningless |
By the firing line, same outdoor
Boulder-area trap range as above, two samples |
217±194 ppm |
262±214 ppm |
239±215 ppm |
From where the shots impact the side
hill, Boulder-area outdoor target range |
57800±11400 ppm |
10600±20600 ppm |
84600±16700 ppm |
Conclusions: For the hand samples, only
one data point was gathered for each hand, and one data point is meaningless.
The fact that the left handÕs lead reading was roughly half the rightÕs reading
is a Òred flag,Ó but more research is needed before drawing any conclusions.
Searches on the web as well as the University of ColoradoÕs Chinook system
yielded discussions of lead contamination and shooting, but nothing on levels
of lead on hands.
Five samples from the middle of a
Boulder-area trap range came in negative, and are taken as indeterminate.
Perhaps the solutions should have been concentrated.
The samples from where the shots impact
the side hill at a Boulder-area range cannot be easily dismissed. As six
samples were run, this has significance. These values are within the order of
magnitude of the figures 4700 to 57000 ppm as one source [11]] reports. The
presence of two shotgun pellets in the highest-reading sample is a Òred flag,Ó
and perhaps the sample was drawn from an area of very high lead content. More
research and samples from a broader area are needed.
The large intercept of the calibration
curve could have come from many sources. Perhaps the instrument was not zeroed
properly, or perhaps the nitric acid or the 18 MW water was contaminated. Of note, the nitric acid had a
guaranteed lead level below 0.05 ppm.
A number of improvements and enhancements
to this research suggest themselves, in no particular order:
Figure 2: The calibration curve.
Note concentration error bars are nearly invisible.
1.
http://www.freep.com/jobspage/academy/guns.htm
2.
http://www.dyerlabs.com/glossary/gun_terms.html
3.
http://www.recguns.com/Sources/IE.html
4. Rowlen K , Chemistry 4181
Laboratory Manual , University of Colorado, 2004, pp. 26-29.
5. http://www.epa.gov/lead/leadhaz.htm
6. http://www.vpc.org/studies/leadone.htm
7.
http://en.wikipedia.org/wiki/Lead
8. www.ewg.org/reports/poisonouspastime/leadpoll.pdf
9. "Gun buffs risk loading lungs with lead," Science News, August 19, 1989, p. 126
10.
www.epa.gov/region02/waste/leadshot/epa_bmp.pdf
11.
http://www.cws-scf.ec.gc.ca/publications/papers/88/chap2_e.cfm
12.
http://www.utexas.edu/safety/ehs/msds/lead.html
13. http://www.co.ba.md.us/Agencies/police/academy/lead_poisoning.html
14. http://www.cws-scf.ec.gc.ca/publications/papers/88/chap3_e.cfm
15. http://www.cws-scf.ec.gc.ca/publications/papers/88/icons/fig11.gif
16. http://www.cws-scf.ec.gc.ca/publications/papers/88/tabl4_e.cfm
17. http://www.ewg.org/reports/poisonouspastime/leadpoll.pdf
18. www.epa.gov/lead/leadtest.pdf
19. http://reason.com/9811/col.lynch.shtml