Comparison of blood lead levels in three groups of Sardinian children.

This paper reports blood lead levels in children from three Sardinian municipalities: Portoscuso, Iglesias, and Sestu. Portoscuso, chosen as the control area, is located about 2 km from one of the most important industrial complexes of the island. Iglesias was once an important zinc-lead mining centre. Sestu is a semi-urban centre located about 10 km from Cagliari (the islands's capital), and may be considered unexposed to lead pollution. Blood lead concentration was evaluated in heparinized venous blood samples by graphite furnace atomic absorption spectrophotometry. Children living in Portoscuso show a higher mean of blood lead levels (8.43 micrograms/dl) as compared to that of children of the same age living in Iglesias (6.92 micrograms/dl) and Sestu (5.71 micrograms/dl). By the Bonferroni t-tests procedure these mean differences appear to be statistically significant. The mean of PbB levels obtained in this investigation for children from Portoscuso showed a decrease of 33.62% with respect to that reported in a previous investigation carried out in 1987 (12.7 micrograms/dl).     

Effects of iron therapy on blood lead concentrations in infants

To determine whether blood lead concentration is elevated in iron-deficient infants, blood lead and serum ferritin concentrations, serum iron/transferring iron-binding capacity (Fe/TIBC) and complete blood counts were measured in 30 iron deficient and 35 control infants, aged 6–24 months. All 30 iron-deficient infants received iron supplementation (ferric hydroxide-polymaltose complex, 6 mg/kg Fe³⁺/day) for 1–6 months. Blood lead concentrations were measured in 18 of the iron deficient infants after their ferritin levels returned to the normal range. The geometric mean blood lead concentration was higher in iron deficient than in control infants (1.846 vs. 1.416 μg/dL). After iron therapy, the blood lead levels of iron-deficient infants decreased significantly compared with pre-treatment levels (1.785 vs. 2.386 μg/dL), and the hemoglobin and ferritin concentrations increased significantly. These findings indicate that iron deficiency increases blood lead concentrations in infants with very low blood lead concentrations.     

Dietary calcium and blood lead levels in women

Nutritional factors are known to influence metabolism and toxicity of several metals in animal experiments, but relevant human data are scarce and inconclusive. In this work, we tested the hypothesis that dietary calcium influences lead metabolism in humans. Blood lead concentrations were used as indicators of lead exposure and metabolism. Two groups of peasant women living in similar conditions in two different regions in Yugoslavia (100 in each) were chosen as subjects for this purpose. In region A, the dietary calcium intake was about 940 mg, and in region B about two times lower, i.e., 450 mg/day. The average blood lead concentration was significantly lower in women from region A (69 micrograms/L) than from region B (83 micrograms/L). Our results support the assumption that adequate calcium intake might be one of the preventive measures for decreasing lead absorption. This new evidence, sought for some time by nutritionists and toxicologists, needs further international confirmation.     

Blood lead concentration,blood pressure,and renal function.

Blood lead concentrations were related to blood pressure and indicators of renal function in a clinical survey of 7735 middle aged men from 24 British towns. There was no overall evidence that blood lead concentrations were associated with systolic or diastolic blood pressure (r = +0.03 and +0.01, respectively). In the 74 men with a blood lead concentration of 1.8 mumol/l (37.3 micrograms/100 ml) or more there was some suggestion of increased hypertension, but this did not reach significance. Blood lead concentration did not have any relation with serum creatinine concentration. Moderate increases in blood lead concentration were associated with small increases in mean serum urate concentration and small decreases in mean serum urea concentration; these associations were both reduced when alcohol consumption was taken into account. There is no indication that exposure to lead at concentrations commonly encountered in British men is responsible for impaired renal function or increased blood pressure.     

Comparison of blood lead concentrations in patients with acute ischemic stroke and healthy subjects

Background and ObjectivesStroke is the main cause of mortality and long-term disability in the general population. With the increased application of metals in industries and human environment, lead has become a health hazard. In this study, we aimed to evaluate the relationship between the blood concentration of lead and the incidence of acute stroke.Materials and MethodsWe performed this study during 2016−17 at Vali-e-Asr Hospital in Birjand, Iran, among 80 ischemic stroke patients visiting the hospital and 80 healthy gender- and age-matched controls. Blood lead concentration (BLC) was measured using graphite furnace atomic absorption spectrometry.ResultsBLC medians in the case and control groups were 20.65 [5.37−34.87] μg/dL and 2.65 [1.75−13.85] μg/dL, respectively (p < 0.05). The case group had significantly lower mean levels of HDL and phosphors, whereas the mean levels of white blood cells and uric acid were higher in this group. After adjusting for lipid profile and fasting blood sugar, multiple logistic regression indicated that the serum levels of uric acid and BLC were significant for predicting ischemic stroke. It is estimated that the odds ratio of ischemic stroke increases by 1.04 per 1 μg/dl increase in BLC.ConclusionThis study showed that lead can be a risk factor for ischemic stroke. Since it does not have any beneficial effects on the health of individuals, screening serum concentrations of lead can be considered as a preventive strategy for those at risk of stroke.     

Low level environmental lead exposure--a continuing challenge

The current threshold for lead toxicity, defined as a blood lead level of 10 mug/dL, was adopted by the United States (US) Centers for Disease Control and Prevention (CDC) in 1991 and the World Health Organization in 1995. Since that time, adverse health outcomes at blood lead levels below this threshold have been well demonstrated. Most concern probably relates to children of pre-school age; an international pooled analysis has demonstrated lead-associated intellectual deficits at blood lead levels well below 10 mug/dL. In the case of adults, several convincing population studies have shown a positive association between blood lead and risk of death. The largest such study compared mortality information from participants with blood lead levels in the highest third of the blood lead distribution (3.6 mug/dL or greater) with those in the lowest third (less than 1.9 mug/dL). After adjustment for potential confounders, estimates of the excess risk were 25% for all cause mortality and 55% for cardiovascular mortality. The adverse consequences of lead exposure have no discernible blood lead threshold, implying there is no safety margin at existing exposure levels. Despite marked declines in population mean blood lead levels since 1980, low level environmental lead exposure remains a significant public health concern.     

Blood lead in children and associations with trace elements and sociodemographic factors

BackgroundNo safe blood lead concentration in children has been identified. Lead can affect nearly every system in the body and is especially harmful to the developing central nervous system of children.The aim of this study is to analyze blood lead in a population of children and its association with sociodemographic variables, biochemical parameters, copper, iron, selenium and zinc.MethodsWe recruited 155 children (86 boys and 69 girls) with a mean age of 7.3 (SD:4.1). Blood lead and serum selenium concentrations were measured by electrothermal atomic absorption spectrometry. Serum copper and zinc concentrations were measured by flame atomic absorption spectrometry. Serum iron levels were determined by colorimetric assay. A risk exposure questionnaire for lead was administered to the participants.ResultsThe median blood lead level was 1.1 (IQR 0.7–1.6) μg/dL. Regarding risk exposure factors, the youngest children (<2 years) who played outdoors presented a median blood lead concentration of 1.1 μg/dL IQR: 0.48–1.48, compared to the median of 0.3 μg/dL IQR:0.2-0.48 in the children who stated they played at home (p = 0.024). Significant differences were also found when taking into account those parents who smoked (median 1.3 IQR 0.8–1.9 μg/dL vs 0.9 IQR 0.5–1.4 μg/dL of non-smokers, p = 0.002). Children who drank tap water had higher blood lead levels (median 1.2 IQR 0.7–1.6 μg/dL) than those who drank bottled water (median 0.7 IQR 0.2–1.3 μg/dL p = 0.014). In addition, children whose mothers had not finished school had higher blood lead levels (median 1.7 IQR 1.2–2.3 μg/dL) than those whose mothers had finished school (median 1.2 IQR 0.7–1.7 μg/dL) and those whose mothers had gone to university (median 0.9 IQR 0.5–1.4 μg/dL) p = 0.034. In the multivariate lineal regression analysis we continue to observe the association between mother’s higher level of education and lower blood levels (p = 0.04) and the interaction between age and outdoor play (p = 0.0145).ConclusionsIn spite of the decline in blood lead concentrations, associated risk factors continue to exist in vulnerable populations such as children.     

Association of newborn blood lead concentration with neurodevelopment outcome in early infancy

BackgroundIn utero exposure to toxic metal substances can cause severe neurodevelopmental deficits in developing fetus and infant.MethodsWe evaluated the association of newborn umbilical cord blood lead concentration with early neurodevelopmental performance (cognitive, receptive language, expressive language, fine motor, gross motor and social-emotional development). The Bayley Scale of Infants Developments-III (BSID-III) was used to perform neurodevelopment outcomes at an average age of 6.5 months. In this prospective study, total of 167 mother-child pairs were enrolled from Western Rajasthan, India. Association between risk factors of lead contamination and newborn umbilical cord blood lead levels was observed. Multivariate regression was performed to see the association of cord blood lead level with infant neurodevelopment outcome.ResultsThe obtained newborn umbilical cord blood lead concentration 5.0–10.5 μg/dL was negatively associated with the sub-scale score of gross motor development (β-coefficient with 95 % CI; −0.29 (−5.0–0.11), p = 0.04). However, no associations were found with the score of cognitive, language, gross motor, and social-emotional development. The umbilical cord blood lead concentration <5.0 μg/dL was also not associated with the BSID-III scores. The mother's regular intake of calcium supplements during the antenatal period was significantly associated with a lower umbilical cord blood lead level (p-value 0.031).ConclusionThe data suggest that newborn umbilical cord blood lead concentration 0.5–10.5 μg/dL has a negative association with early gross motor development during infancy.     

Association of blood lead levels with neurobehavior and BDNF expression in school going children

BackgroundChildhood Lead (Pb) toxicity has been an ongoing concern for decades; however, its underlying pathogenesis remains unclear. Although its prevalence has come down in developed countries (USA, Europe); it is relatively high in low to middle-income countries of South-East Asia. The current study aimed to evaluate the association of blood lead levels (BLLs) with neurobehavioral alterations and changes in Brain-Derived Neurotropic Factor (BDNF) expression in Indian school children.MethodologySchool going children in age group of 9–15 years (N = 72) were included in the study. Neurobehavioral changes were assessed using Childhood Psychopathological Measurement Schedule (CPMS) and BLL were measured by Graphite Furnace Atomic Absorption Spectrophotometry (GFAAS). BDNF mRNA expression and serum BDNF levels were assessed by Real-Time PCR and ELISA, respectively.ResultsMedian BLL was 4.95 μg/dL (IQR = 4.47), very close to the recommended toxic cut off levels (<5 μg/dL). BLLs had a direct correlation with both CPMS scores and BDNF expression. Depression was found to be significantly higher in boys than in girls with high BLLs. BDNF mRNA expression and serum BDNF levels were higher among children with high BLL, although not to significant levels.ConclusionWe report a significant association of neurobehavioral changes with the prevalence of high Pb levels in Indian children. Additionally significant correlation of BDNF with BLL in these children suggests a causal role of BDNF in Pb induced neurological damage.     

Is lead in tap water still a public health problem? An observational study in Glasgow.

OBJECTIVE: To assess the relation between tap water lead and maternal blood lead concentrations and assess the exposure of infants to lead in tap water in a water supply area subjected to maximal water treatment to reduce plumbosolvency. DESIGN: Postal questionnaire survey and collection of kettle water from a representative sample of mothers; blood and further water samples were collected in a random sample of households and households with raised water lead concentrations. SETTING: Loch Katrine water supply area, Glasgow. SUBJECTS: 1812 mothers with a live infant born between October 1991 and September 1992. Blood lead concentrations were measured in 342 mothers. MAIN OUTCOME MEASURES: Mean geometric blood lead concentrations and the prevalence of raised tap water lead concentration. RESULTS: 17% of households had water lead concentration of 10 micrograms/l (48.3 nmol/l) or more in 1993 compared with 49% of households in 1981. Tap water lead remained the main correlate or raised maternal blood lead concentrations and accounted for 62% and 76% of cases of maternal blood lead concentrations above 5 and 10 micrograms/dl (0.24 and 0.48 mumol/l) respectively. The geometric mean maternal blood lead concentration was 3.65 micrograms/dl (0.18 mumol/l) in a random sample of mothers and 3.16 micrograms/dl (0.15 mumol/l) in mothers whose tap water lead concentrations were consistently below 2 micrograms/l (9.7 nmol/l). No mother in the study had a blood lead concentration above 25 micrograms/dl (1.21 mumol/l). An estimated 13% of infants were exposed via bottle feeds to tap water lead concentrations exceeding the World Health Organisation''s guideline of 10 micrograms/l (48.3 nmol/l). CONCLUSIONS: Tap water lead and maternal blood led concentrations in the Loch Katrine water supply area have fallen substantially since the early 1980s. Maternal blood lead concentrations are well within limits currently considered safe for human health. Tap water lead is still a public health problem in relation to the lead exposure of bottle fed infants.     

Hormonal effects of lead acetate in the male rat: mechanism of action

Environmental exposure to toxic levels of lead occurs in a number of industries with potential adverse effects on the reproductive capacity of exposed men. Using a rat model, we previously reported that dietary exposure to lead resulted in suppressed spermatogenesis and testosterone levels without significant changes in luteinizing hormone (LH). In this study, to identify more specifically the site of lead's toxic actions on the hypothalamic-pituitary-testicular axis, the response of lead-treated male rats as compared to control animals to naloxone, gonadotropin-releasing hormone (GnRH), and LH stimulation was studied. Three groups of 52-day-old Wistar rats were allowed access to either deionized distilled water containing no lead acetate or a 0.3% lead acetate solution for 30 days. In each study group, 10 control and 10 lead-treated animals were anesthetized prior to cardiac puncture and collection of serum for the measurement of lead level and baseline LH (Groups I and II) or testosterone levels (Group III). In Group I, 20 min after an i.p. injection of naloxone (1.5 mg/kg/BW), the animals were killed by decapitation, and serum was collected for LH measurement. Thirty minutes after an i.p. injection of GnRH (100 ng/100 gm BW), Group II animals were killed by decapitation, and serum was collected for LH. Sixty minutes after an injection of LH (100 mg/100 mg BW), serum was collected from Group III animals for testosterone measurement. All control animals and lead-treated animals consumed similar volumes of water. Control animals had undetectable levels of lead in their blood. Lead-treated animals had mean blood lead values of 30 micrograms/dl +/- 5 micrograms/dl.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma and erythrocyte lipid peroxide levels in workers with occupational exposure to lead

The plasma and erythrocyte lipid peroxide levels were measured in a group of male subjects occupationally exposed to lead for an average period of 17 yr, and compared to those from an age-matched control group living in the same city in a similar socioeconomical environment. The blood lead and plasma zinc levels were measured by atomic absorption spectroscopy. The plasma and erythrocyte lipid peroxide levels were established by the malondialdehyde determination method. Significant differences were found in the blood lead levels in lead-exposed workers, 15.00±10.15 μg/dL as compared to controls, 2.37±0.89 μg/dL. The plasma (2.67±0.69 μM) and erythrocyte (27.53±6.28 nmol/g Hb) lipid peroxide levels in workers with occupational exposure to lead were significantly higher than controls, 1.23±0.61 μM and 14.35±2.08 nmol/g Hb, respectively. There were no significant differences of the zinc levels in both groups. The blood lead levels had a statistically significant positive correlation with age and with duration of exposure in both groups, but showed no relationship to the corresponding blood zinc levels. The results presented in this study indicate that the increase of plasma and erythrocyte lipid peroxide levels in workers exposed to lead may be related to the lead concentration, age and duration of exposure.     

Effects of lead on luteal function in rhesus monkeys

Exposure to lead in the workplace or home environment has been implicated as a cause of decreased fertility in women. In a previous study, as part of our effort to determine effects of lead in primates, female rhesus monkeys were exposed to lead acetate in drinking water (n = 10) or provided water with no added lead (n = 7) for 33 mo. Lead was administered at levels between 2 and 8 mg/kg/day, with doses adjusted to keep blood lead values near a target of 70 micrograms/dl (observed mean +/- SEM = 68.9 +/- 6.54 micrograms/dl). Blood lead concentrations in control animals were less than 10 micrograms/dl. No significant differences were detected between control and experimental animals in body weight, hematocrit, or general health. Female monkeys receiving lead exhibited longer and more variable menstrual cycles and shorter menstrual flow. In the present study, circulating amounts of progesterone (P4) were determined to evaluate luteal function during the final 7 mo of treatment with lead. Several characteristics were altered as a result of lead treatment: circulating amounts of P4 were reduced as indicated by relative units of area under the concentration-time curve, maximal amounts of P4 were reduced, and P4 levels were greater than 1 ng/ml on fewer days. There were no significant differences between groups in mean percent of anovulatory cycles. Therefore, although chronic treatment with the levels of lead used in this study did not prevent ovulation, luteal function was suppressed. These results extend previous observations of adverse effects of lead on ovarian activity and fertility in monkeys.     

Activity of glutathione peroxidase, glutathione reductase, and lipid peroxidation in erythrocytes in workers exposed to lead

The aim of this study was to estimate the activity of glutathione peroxidase (GPx), glutathione reductase (GR), and malondialdehyde (MDA) in erythrocytes in healthy male employees of zinc and lead steelworks who were occupationally exposed to lead over a long period of time (about 15 yr). Workers were divided into two subgroups: the first included employees with low exposure to lead (LL) (n=75) with blood lead level PbB=25–40 μg/dL and the second with high exposure to lead (HL) (n=62) with PbB over 40 μg/dL. Administration workers (n=35) with normal levels of PbB and zinc protoporphyrin in blood (ZPP) in blood were the control group. The activity of GPx significantly increased in LL when compared to the control group (p<0.001) and decreased when compared to the HL group (p=0.036). There were no significant changes in activity of GR in the study population. MDA erythrocyte concentration significantly increased in the HL group compared to the control (p=0.014) and to the LL group (p=0.024). For the people with low exposure to lead (PbB=25–40 μg/dL), the increase of activity of GPx by about 79% in erythrocytes prevented lipid peroxidation and it appears to be the adaptive mechanism against the toxic effect of lead. People with high exposure to lead (with PbB over 40 μg/dL) have shown an increase in MDA concentration in erythrocytes by about 91%, which seems to have resulted from reduced activity of GPx and the lack of increase in activity of GR in blood red cells.     

Factors associated with blood zinc,chromium, and lead concentrations in residents of the Nam Pong River in Thailand

This cross-sectional analytical study aimed to determine the blood levels of zinc (B-Zn), chromium (B-Cr), and lead (B-Pb) and to identify the factors influencing these levels in the blood of residents of the Nam Pong River. Quantitative data collection was utilized, and systematic random sampling was conducted to obtain 420 samples for measuring serum heavy metals, including B-Zn, B-Cr, and B-Pb. Multiple regression analysis was used to identify factors influencing the accumulation of heavy metals in the population, reported mean differences, 95% confidence intervals, and p values. The average levels of heavy metals were 74.38 ± 14.00 µg/dL (95% confidence interval [CI]: 73.03–75.72) for zinc, 0.28 ± 0.23 µg/L (95% CI: 0.26–0.30) for chromium, and 2.80 ± 1.60 µg/dL (95% CI: 2.64–2.95) for lead, which all were within normal limits. Factors influencing zinc levels included occupational exposure (batteries) (mean diff = 11.56; 95% CI: 1.81–21.32, p value = 0.02) and consumption of fish from the river exceeding 300 grams/meal or three times/week (mean diff = 4.68; 95% CI: 0.09–9.45, p value = 0.05). Factors influencing chromium levels included a history of past illness (mean diff = 0.19; 95% CI: 0.05–0.34, p value = 0.01) and dust/chemical exposure from industry (mean diff = 0.05; 95% CI: 0.00–0.11, p value = 0.05). Factors influencing lead concentrations included gender (mean diff = 1.82; 95% CI: 0.26–1.98, p value = 0.001), smoking (mean diff = 1.03; 95% CI: 0.60–1.45, p value < 0.001), and occupational exposure (garage) (mean diff = 1.11; 95% CI: 0.27–1.94, p value = 0.01).     

Blood lead level and nutritional status indicators in preadolescent Polish schoolchildren

BackgroundEnvironmental pollutions with heavy metals may have toxic effects on human health and development. One of the most detrimental is lead exposure, which may disturb neurodevelopment and linear growth in children. However, data on the effect of lead exposure on nutritional and weight status in children are limited, thus this study aimed to assess the effect of blood lead (Pb) level on nutritional and weight status in preadolescent schoolchildren from the industrialized, mining region in southwestern Poland.MethodsOur study sample involved N = 709 schoolchildren (402 boys and 307 girls) in the preadolescent developmental period (7–11 years of age for boys and 7–10 years of age for girls). Anthropometric measurements were used to assess nutritional and weight status: body mass index (BMI), mid-upper arm circumference (MUAC) and skinfolds thicknesses (triceps, subscapular, abdominal and the sum of skinfolds). Blood Pb level was evaluated and divided into two groups: above (>3.7 μg/dL) and below median value (≤3.7 μg/dL).ResultsAnalysis of covariance (with children’s age controlled as a covariate) revealed that children with blood Pb level above median value had significantly lower values of BMI, MUAC and all skinfolds (at least p < 0.01). However, this effect was significant only in boys, whereas in girls differences were non-significant (p > 0.05). The highest effect size of blood Pb level was noted for skinfolds thicknesses (partial η²: 0.015 for the sum of skinfolds).ConclusionsNutritional status in children with higher blood Pb level is significantly impaired in preadolescent boys, who appear to be more sensitive to this environmental factor. Our findings indicate a particular need for nutritional and environmental interventions among preadolescent children in regions with higher lead exposure.     

Daily rhythms in blood and milk lead toxicokinetics following intravenous administration of lead acetate to dairy cows in summer

The objective of this study was to investigate circadian variations of blood and milk lead toxicokinetics in dairy cows in summer. Twenty lactating Holstein animals were randomly assigned to four treatments corresponding to different hours after onset of light (HALO): 2, 8, 14, and 20. Cows received a single intravenous administration of 2.5 mg/kg lead as lead acetate. Blood and milk samples were taken and analyzed by atomic absorption spectrophotometry. For each toxicokinetic parameter, a one-way analysis of variance (ANOVA) was performed to outline the existence of daily variations. Significant blood differences as a function of HALO were found for the hybrid constant of distribution (α), hybrid constant of elimination (β), elimination half-life (), area under the curve (AUC), volume of distribution at steady state (V_ss) and clearance (Cl_B) (p<0.05). Half-life of elimination presented two peaks at 2 and 14 HALO. Milk data showed significant differences for maximum concentration and AUC (p<0.05). The ratio AUC_milk/AUC_blood was utilized to estimate penetration of lead in milk. It differed significantly throughout the day (p<0.05). Milk data for the significant parameters could be fitted to circadian rhythms. No circadian rhythms were detected in blood parameters or in the ratio AUC_milk/AUC_blood.     

A preliminary clinical investigation into the potential of blood lead levels to measure bone resorption in patients with skeletal metastases, using ICP-MS.

A simple, accurate and precise method to measure lead levels in whole blood by inductively coupled plasma-mass spectrometry (ICP-MS) has been developed. Blood samples were diluted (1 + 9) with 0.1% v/v Triton X-100 and 0.1% v/v nitric acid, and gave a limit of detection of 0.06 microgram/l (3sn). Spiking experiments demonstrated recoveries of 100 +/- 10% and verification against Seronorm reference and BCR certified reference materials gave experimental values in close agreement to the reference values. The methodology was used to conduct a feasibility study, involving a preliminary clinical investigation to assess the potential of whole blood lead levels as biochemical markers to measure bone resorption in patients with skeletal metastases and receiving treatment. The results from this feasibility study showed that the method remained under analytical control, giving inter and intra assay coefficients of variation of < 5%. This feasibility study also showed that the changes in the blood lead levels within individual patients were measurable and in many cases the patient's observed clinical performance demonstrated similar trends to the blood lead levels measured over time. Overall the results were encouraging and showed promise. Further and more detailed investigations into the use of lead and other trace metals as biomarkers of bone resorption is warranted.     

Effect of lead on blood protoporphyrin levels of a group of ring teal ducks (Callonetta leucophrys)

This research determined the relationships between blood lead level and zinc protoporphyrin (ZnPROTO), protoporphyrin IX (PROTO), and free erythrocyte protoporphyrin (FEP) levels in a group of 18 ring teal ducks. Blood samples were drawn from two groups of ring teal ducks as part of the routine health maintenance program of the New York Zoological Park. One group of six teals had been exposed to what is believed to be lead-contaminated dust, while the second group of twelve teals was unexposed. Blood samples were analyzed for lead by flameless atomic absorption and for protoporphyrins by fluorescence. Blood lead level and log blood lead level had positive correlations with each of the protoporphyrins: the logarithmic correlations were better than the nonlogarithmic correlations, and PROTO correlated better than ZnPROTO. With one exception, PROTO levels were higher than ZnPROTO levels. The results suggest that PROTO, FEP, or ZnPROTO could serve as a biological indicator of lead poisoning in ring teal ducks.