Page 90 - JSOM Spring 2018

with those with BLL less than 5μg/dL. Independent evalua- symptoms; however, it reflects recent exogenous exposure
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tion of the people age 17 years or older in the same cohort (n (i.e., the past 30 days) more than endogenous equilibration
= 13,946) found that BLL of at least 3.62μg/dL compared with from bone stores. Therefore, BLL is not a reliable indica-
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BLL less than 1.94μg/dL was associated with a hazard ratio of tor of cumulative dose, temporality of exposure, or end-organ
1.55 for cardiovascular mortality and 1.25 for all-cause mor- toxicity. BLL is superior to lead levels measured using urine,
tality. Thorough evaluation of these data has been determined hair, or other sources, and capillary samples should be avoided
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sufficient to ascribe causal association of lead exposure with because of skin surface contamination. Periodic testing or
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several specific cardiovascular health effects and that the rela- biologic monitoring of BLL demonstrates temporality of ex-
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tionship develops at a BLL less than 10μg/dL. 30 posure and may be used to monitor for continued exposure or
response to treatment.
Central and peripheral nervous system dysfunction is another
proven health effect of lead toxicity and may be one of the Other Tests
most concerning for SOF. Lead has been shown to affect cog- A patient diagnosed with lead poisoning may require further
nitive and psychomotor performance, mood, and the auditory, testing, such as CBC count, blood smear, urinalysis, and blood
visual, and balance systems dose dependently. Increasing con- urea nitrogen, serum creatinine, hepatic aminotransferases,
3
centrations of blood lead and patella bone lead (a biomarker and free erythrocyte protoporphyrin or zinc protoporphyrin
for cumulative lead exposure) have been correlated with cog- (ZPP) levels. The Occupational Safety and Health Administra-
nitive decline and neurologic deficits. A cross-sectional analy- tion (OSHA) lead surveillance program requires ZPP moni-
sis of lead-exposed workers (n = 803) and unexposed control toring. CBC count with smear morphology may demonstrate
subjects (n = 135) found that a BLL increase of 5μg/dL was hemolytic anemia in the context of acute exposure, basophilic
equivalent to 1.05 years of cognitive age–related decline, us- stippling with subacute exposure, and hypochromic, normo-
ing eight separate measures of the World Health Organization cytic, or microcytic anemia with chronic poising. Free eryth-
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Neurobehavioral Core Test Battery. A longitudinal analysis rocyte protoporphyrin and ZPP measure the effect of lead on
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of men (n = 1,089) in the Normative Aging Study demon- hemoglobin synthesis. ZPP positivity may lag BLL elevation
strated that bone lead increases were predictive of worsening by several weeks and may remain elevated for the life cycle of
reaction-time scores on visuospatial and visuomotor tests. red blood cells (approximately 120 days). K-shell X-ray fluo-
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Thorough review of current data has shown that lead-related rescence (KXRF), dual-energy x-ray absorptiometry scans, or
symptoms can be detected at BLLs as low as 12μg/dL and that other markers of bone lead are not recommended for clinical
cognitive effects of lead exposure may be present years after diagnosis and treatment. KXRF is used for research purposes
cessation of occupational lead exposure. only.

Low-level lead toxicity increasingly has been associated with Providers who suspect lead poisoning, especially in the pres-
a host of other maladies, including reproductive dysfunction. ence of diminished cognitive function and elevated BLL, should
The fetus and neonate are exposed to lead when it crosses the include neurobehavioral testing as part of their examination.
placental barrier or is present in breast milk. A case-control Neurobehavioral testing can elucidate deficits characteristic
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study of pregnant women (n = 668) found BLLs of 5–9, 10–14, of lead toxicity in manual dexterity, perceptual motor speed,
and greater than 15μg/dL to have odds ratios for spontaneous mood, and memory. 44,45 Specifically, cognitive performance
abortions of 2.3, 5.4, and 12.2, respectively, after matching for may be measured via simple reaction time, by the Mini-Mental
age, gestational age, education, and other covariates. Mater- State Examination, and by neurobehavioral tests. Signs of pe-
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nal lead exposure has been found to affect children’s physical ripheral neuropathies may be revealed by measuring the effects
development prenatally, and multiple prospective studies have of vibrational perception in the hand and foot. In addition,
46
elucidated deleterious effects on neurobehavioral development changes in the auditory, visual, and balance systems can be
throughout early childhood. Lead has also been associated correlated with lead toxicity and may require thorough evalu-
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with abnormal sperm morphology and decreased sperm count ation and testing.
in men. 40
Treatment
Diagnosis of Lead Poisoning
Treatment for lead toxicity begins with cessation of exposure.
Medical practitioners should take a thorough exposure history The patient should be removed from any work or training
from any patient presenting with signs or symptoms of lead that entails lead exposure, and the necessary decontamination
poisoning. History should include employment, hobbies, use should be performed. In the case of acute ingestion, whole-
of personal protective equipment, hygiene practices, smoking bowel irrigation and mechanical removal should be consid-
and eating environments, and previous exposures to lead. An ered. Retained bullets should also be considered for surgical
14
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appropriate expectation is that anyone within the Special Op- removal. Once the patient is no longer exposed and supportive
erations community is potentially exposed, especially given the care is provided, chelation therapy may be considered.
poorly regulated environments found during foreign deploy-
ments. A thorough physical examination should be conducted Chelation therapy may accelerate urinary lead excretion and
to assess for signs that correlate with lead exposure. Indeed, a reduce blood lead concentrations but will have limited effect
detailed neurologic examination can reveal the manifestations on bone and total-body lead levels. Although anecdotal evi-
of lead toxicity. dence suggests that chelation may treat symptoms and reduce
mortality risk, there are no data from randomized trials of
BLL is the most common test for monitoring lead exposure chelation therapy on long-term health outcomes. Further-
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and toxicity, and can be used to guide clinical management. more, BLL may equilibrate after chelation, causing a rebound
At levels above 40–80μg/dL, BLL may correlate with clinical of blood concentration.

84 | JSOM Volume 18, Edition 1/Spring 2018