Urinary Delta-aminolevulinic Acid Research Articles

Evaluation of calcium excretion in Brazilian infantile and young population environmentally exposed to lead

Lead exposure is an important issue in the research of several toxic effects resulting from the biochemical interaction between this metal and the organism. Calcium is a fundamental mineral for the maintenance of the organism homeostasis where there is interaction between lead and calcium in metabolic pathways. Environmental lead exposure by verifying the usefulness and applicability of urinary calcium/creatinine ratio (UCa/Cr) in this context was evaluated. This was an extensive socio-demographic study of the nutritional profile, lead exposure biomarkers in blood and the urine and UCa/Cr ratio. The children studied were from a low socio-economic group characterized by unsatisfactory nutritional diet. Lead environmental exposure was shown by biomarkers, with UCa/Cr ratio having positive and significant correlations with both lead and delta-aminolevulinic acid in urine (ALA-U), without colinearity diagnosis. There was a strong association between calcium excretion and lead exposure as a result of linear regression construction models. In children, lead increases calcium excretion which is an additional risk to infantile health. Urinary calcium/creatinine ratio may be a useful tool in the biological monitoring of lead exposure and health promotion programs.

Lead Exposure and Indicators of Biological Effect

ISEE-193 Objective: The medical literature shows that both occupational and environmental exposure to lead affect the human health. Clinical manifestations appear when the absorbed lead is higher than the eliminated lead, generating the acute or chronic intoxication. The aim of this study was to analyze comparatively, using some specific and precocious affected biological indicators, 2 groups of people occupationally and environmentally exposed to lead. Material and Methods: We investigated 195 workers from a nonferrous metallurgical plant (mean = 31.81 ± 8.19 years and meantime of exposure = 9.03 ± 6.67 years), and 255 people who live in the proximity (mean = 35.66 ± 8.49 years and meantime of exposure = 7.73 ± 6.16 years). We carried out clinical, neurological, and psychological examinations, biotoxicologic investigations, urinary delta amino levulinic acid (ALA-u), zinc protoporphyrin (ZPP), and standard questionnaires regarding the effects of lead on the human organism. The air lead exceeded 71.3 times the maximum accepted values. Results: We found high values of ZPP (over 10 μg/L) in 78.6% of exposed workers and 28.2% of people from the environmental group. In the environmental group, aged 20 to 35 years and length of service under 5 years, 19.1% had ZPP over 10 μg/L. High values of ALA-u (over 10 mg/L) were found in 68.1% of exposed workers and 27.4% from the environmental group. In the group aged 20 to 35 years and had length of service under 5 years, 62.9% workers and 16.6% controls had values over 10 mg/L. There were concordance between ZPP and ALA-u values (r = 0.567, P < 0.001). Conclusions: There were significant differences between the exposed and environmental group regarding the values of the intoxication marker ZPP (P < 0.001) and the values of ALA-u, which is specific for the lead intoxication (P < 0.001). There were also significant differences regarding ZPP and ALA-u values between the 2 groups (aged 20–35 years and working length under 5 years) (P < 0.001). The most affected were the younger people. The general and professional morbidity correspond with the clinical and toxicologic data.

Environmental lead exposure and its relationship to traffic density among Senegalese children: a cross-sectional study

Leaded-gasoline is probably the primary source of lead (Pb) exposure in Dakar (Senegal). The present cross-sectional study was undertaken to investigate the levels of Pb in Senegalese children and to present helpful data on the relationship between Pb levels and changes in biological markers of heme biosynthesis and oxidative stress. A total of 330 children, living since birth either in rural or urban areas (ie, Khombole (n = 162) and Dakar (n = 168), respectively) were included. During this cross-sectional study, the mean blood (B)-Pb level in all children was 7.32 +/- 5.33 microg/dL, and was influenced by the area of residence and gender. In rural children, 27 subjects (16.7%), 18 boys (19.6%) and nine girls (12.9%), had a B-Pb level > 10 microg Pb/dL, whereas 99 urban children (58.9%), respectively, 66 boys (71.8%) and 33 girls (43.4%), had alarmingly high B-Pb levels. Accordingly, urine delta-aminolevulinic acid levels were higher in children living in the urban area than in the rural areas (P < 0.001), and closely correlated with the B-Pb levels (P < 0.01). Moreover, glutathione peroxidase (GPx) activity, selenium (Se) level, glutathione reductase (GR) activity, and glutathione status were significantly influenced by area of residence and/or by gender. GPx activity and Se level were not only negatively correlated with B-Pb levels, but also positively correlated together (P < 0.01). Taken together, the present results allow us to conclude that urban children have higher B-Pb levels than rural children, and that of these children, boys have higher B-Pb levels than girls, leading thereby to alterations of heme biosynthesis and pro-oxidant/antioxidant balance. We also suggest that exposure to Pb and the Pb-induced adverse effects merits attention and that the development of preventive actions are of increasing importance in Senegal.

Comparison of Colorimetric and HPLC Methods for Determination of .DELTA.-Aminolevulinic Acid in Urine with Reference to Dose-Response Relationship in Occupational Exposure to Lead

Both traditional colorimetry and recently developed HPLC-fluorometry have been in use for determination of delta-aminolevulinic acid in urine (ALA-U), an effect marker of occupational exposure to lead (Pb). The present study was initiated to compare the values by the two methods on an epidemiology basis among workers occupationally exposed to lead (Pb), to estimate quantitatively the colorimetry-associated increment over the values by the HPLC method, to evaluate ALA-U determination in occupational health service for Pb-exposed workers, and to identify a critical Pb-B to induce an elevation in ALA-U. For this purpose, blood and urine samples were collected from three groups of Pb-exposed workers (both men and women in combination, including smokers) and analyzed for Pb in blood (Pb-B; measured in all subjects) and ALA-U (by colorimetry or HPLC), i.e., Group 1 (164 subjects with urinalysis by the two methods), Group 2 (2,923 subjects by colorimetry), and Group 3 (2,540 subjects by HPLC). ALA-U when measured by colorimetry was higher than the values by HPLC, and that the mean difference on a group basis was 1.4 mg/l (in a range of 1.1 to 1.8 mg/l), irrespective of Pb-B levels. It was also found that the increase in ALA-U was small when Pb-B was relatively low (e.g., < or = 40 microg/100 ml), and that the increase on a group basis in response to an increase in Pb-B from 5 to 40 microg/100 ml was as small as < or = 0.6 mg/l. Thus, ALA-U appeared to be not a sensitive marker of Pb effects at low Pb-B levels. ALA-U however increased substantially with a point of inflection at the Pb-B level of about 17-34 microg/100 ml. Thus it was concluded that ALA-U as measured by colorimetry is greater than ALA-U by HPLC by 1.4 mg/l on average irrespective of intensity of Pb-exposure, which may induce bias in evaluation of health effect, and that ALA-U levels will increase when Pb-B is in excess of 17-34 microg/100 ml.

Environmental lead exposure and its relationship to traffic density among Senegalese children: a pilot study.

In Senegal, as in many developing countries, traffic density is increasing in urban areas; in Dakar more than 50% of vehicles use gasoline. Yet the extent and real magnitude of the problem has neither been recognized nor assessed in these countries. Systemic data assessment of lead pollution and people's exposure are not well known in Senegal. This study was also designed to determine the impregnation levels of the lead released by the exhaust of cars and the changes of some early biological markers in Senegalese children. Blood lead (BPb) levels showed that all the children enrolled were exposed. However, lead exposure levels (from 34.7 to 145.8 microg/L) were less important for children living in rural areas (60.9+/-18.3 microg/L) than for those living in urban areas (106.7+/-16.9 microg/L). These changes could be correlated to the difference in the automobile traffic between both these regions (P < 0.001). BPb mean levels found in boys were higher than those in girls (P < 0.05). Despite elevated BPb levels, all values for blood zinc protoporphyrin and urine delta-aminolevulinic acid were within physiological ranges. In addition, variations in some biological markers of oxidative stress and renal disorders were seen; however, they must be confirmed by a future epidemiological study.

Measurement of urinary porphyrins and porphyrin precursors in Dutch hospital laboratories: a review of quality control over 5 years.

We evaluated a quality control scheme for the measurement of urinary uroporphyrin, coproporphyrin, total urinary porphyrins and precursors of urinary porphyrins, delta-aminolevulinic acid and porphobilinogen that was performed in The Netherlands during a period of 5 years. Six quality control samples were distributed each year to the participating laboratories. Mean concentrations and the corresponding coefficients of variation were calculated. Coefficients of variation varied widely and were very high in the concentration ranges that can be found in patients with low-grade porphyria. Commutable calibrators are needed to improve the laboratory diagnosis of porphyria.

Correlation between lead exposure indicators and sister chromatid exchange (SCE) frequencies in lymphocytes from inorganic lead exposed workers.

Inorganic lead exposure was studied in 31 volunteers employed in storage battery plant. The genotoxicity of lead was measured in terms of sister chromatid exchange (SCE). Erythrocyte delta-aminolevulinic acid dehydrogenase (ALAD) activity, urinary delta-aminolevulinic acid (U-ALA), and blood lead levels (PbBs) were also determined to evaluate some possible relations between these lead exposure indicators and the observed SCE frequencies. Blood lead concentration of 36.31 microg/dl was determined as an average level in the workers. Consequently decreased ALAD activity in erythrocytes and increased U-ALA excretion was observed in statistically higher PbBs when compared with the control group. A statistically significant correlation was observed between the PbBs and SCE frequencies (p < 0.05). Moreover, the correlation between U-ALA excretion and SCE frequencies (p < 0.01) was relatively higher than the correlation between PbBs and SCE frequencies. These results might indicate a possible mechanism of ALA mediation in the genotoxic effects of lead.

Toxic effects of arsenic (III) on some hematopoietic and central nervous system variables in rats and guinea pigs.

To evaluate the effects of arsenic (III) exposure on porphyrin metabolism and the central nervous system supplemented with data on the effect of hepatic and renal tissues of rats and guinea pigs. Rats and guinea pigs were exposed to 10 or 25 ppm arsenic in drinking water for 16 weeks. Following chronic arsenic (III) exposure, delta-aminolevulinic acid dehydratase activity in blood showed a significant reduction as did the total cell counts (RBC and WBC) and reduced glutathione with increased urinary delta-aminolevulinic acid. Zinc protoporphyrin, a sensitive indicator of iron deficiency and impairment of heme biosynthesis, showed a significant increase in arsenic exposure. The hepatic delta-aminolevulinic acid dehydratase and delta-aminolevulinic acid synthetase activity increased in chronic arsenic (III) exposure in rats and guinea pigs. Significant changes in the steady-state level of three major neurotransmitters, dopamine, norepinephrine, and 5-hydroxytryptamine, and monoamine oxidase were observed following chronic arsenic (III) exposure. At low doses (10 and 25 ppm in drinking water), the effects of arsenic on hematopoietic indices and whole-brain neurotransmitter concentrations were more prominent in guinea pigs than in rats with some variability in the dose response.

Biomarkers of lead exposure.

Biomarkers of exposure, effect, and susceptibility are reviewed in relation to lead exposure. Of the biomarkers of lead exposure, blood lead (Pb-B), mainly red cell lead, is a representative of soft tissue lead, and most widely used as measures of body burden and absorbed (internal) doses of lead. Urine lead (Pb-U) as well as plasma lead (Pb-P) increases exponentially with increasing Pb-B under a steady-state situation and is a reflection of recent exposure. The amount of lead in plasma and urine (MPb-P and MPb-U) after administration of a chelating agent (e.g. CaEDTA) can be useful for biomarkers of internal exposure of lead, reflecting the mobilizable pool of lead which consists of mainly blood and soft tissue lead with only a small fraction derived from bones. The critical effects in bone marrow arise mainly from the interaction of lead with some enzymatic process responsible for heme synthesis. The effects can be used for the biomarkers of effects. They are the inhibition of delta-aminolevulinic acid dehydratase (ALAD) and the variation in some metabolite concentrations (e.g. delta-aminolevulinic acid in urine (ALA-U), blood (ALA-B) or plasma (ALA-P), coproporphyrin in urine (CP), zinc protoporphyrin (ZP) in blood). The activities of pyrimidine nucleotidase (P5'N) and nicotinamide adenine dinucleotide synthetase (NADS) in blood are also decreased in lead exposure, and nucleotide contents in blood is altered in lead exposure. These effects of lead on human can be also useful biomarkers of effect. The differences in levels of heme precursors between two types of ALAD genotypes might be attributable to those in the affinity of different ALAD isozymes to lead. ALAD1 homozygotes have higher levels of ZP and ALA in comparison with ALAD2 carriers at the high lead exposure, suggesting that ALAD1 homozygotes might be more susceptible for disturbance in heme biosynthesis by lead than ALAD2 carriers.

Blood lead level to induce significant increase in urinary delta-aminolevulinic acid level among lead-exposed workers: a statistical approach.

The present study was initiated to examine the quantitative relationship between blood lead (Pb-B) and urinary delta-aminolevulinic acid (ALA-U) among Pb-exposed workers, and to find a threshold Pb-B level to induce an increase in ALA-U. For this purpose, pairs of venous blood and spot urine samples were collected from 8,274 men and 5,856 women (14,130 workers in total) who were occupationally exposed to inorganic lead. The blood and urine samples were analyzed for Pb-B and ALA-U by atomic absorption spectrometry and colorimetry, respectively, and the correlation between pairs of measures were subjected to statistical analysis. The assumption of the 3rd degree regression for correlation gave a substantially greater correlation coefficient (0.645 for men and 0.619 for women) than 1st or 2nd degree regression, whereas only very small improvement in the coefficient was achieved with 4th to 6th degree ones. Logarithmic conversion of the parameters was not effective in improving the correlation. The assumption of the 3rd degree regression followed by calculation of the local minimum gave 22, 29 and 23 micrograms/100 ml Pb-B for men, women, and men + women, respectively, as the threshold Pb-B to induce ALA-U increase. Pb-B to elevate ALA-U to the 95% upper normal limit (8 mg/l, common to men and women) was 62, 50 and 58 micrograms/100 ml for men, women and men + women, respectively. The validity of the 3rd degree regression assumption as a tool to calculate a threshold from experimental or epidemiological data is discussed.

Relationship between blood lead level and urinary ALA level in workers exposed to very low levels of lead.

The relationship between blood lead (PbB) level and urinary delta-aminolevulinic acid (ALAU) level was examined in a total of 3,636 lead-exposed workers in a periodic medical examination in 1992, in accordance with the Ordinance on Prevention of Lead Poisoning. The results were consistent with previously reported results in that ALAU level was found to increase with an increase in PbB level above 22.4 micrograms/dl (1.35 as a logarithmic value) and to rise markedly above 35.5 micrograms/dl (1.55). On the contrary, the geometric means of ALAU levels appeared to decrease with an increase in PbB levels within a range between a logarithmic value of 0.15 (1.4 micrograms/dl) and 1.25 (17.8 micrograms/dl). Because the earliest sign of the adverse health effects of lead is reported to occur at a PbB level of of 20 micrograms/dl, the relationship between PbB level and ALAU level was examined at PbB levels below 20 micrograms/dl. A regression formula was obtained, Y (log ALAU (mg/l)) = -0.0570X (log PbB (microgram/dl) + 0.4099. This result indicates that ALAU level decreases with a concomitant increase in PbB level lower than 20 micrograms/dl.

Biochemical differentiation of the porphyrias

Objectives: To differentiate the porphyrias by clinical and biochemical methods. Design and methods: We describe levels of blood, urine, and fecal porphyrins and their precursors in the porphyrias and present an algorithm for their biochemical differentiation. Diagnoses were established using clinical and biochemical data. Porphyrin analyses were performed by high performance liquid chromatography. Results and conclusions: Plasma and urine porphyrin patterns were useful for diagnosis of porphyria cutanea tarda, but not the acute porphyrias. Erythropoietic protoporphyria was confirmed by erythrocyte protoporphyrin assay and erythrocyte fluorescence. Acute intermittent porphyria was diagnosed by increases in urine delta-aminolevulinic acid and porphobilinogen and confirmed by reduced erythrocyte porphobilinogen deaminase activity and normal or near-normal stool porphyrins. Variegate porphyria and hereditary coproporphyria were diagnosed by their characteristic stool porphyrin patterns. This appears to be the most convenient diagnostic approach until molecular abnormalities become more extensively defined and more widely available.

Lead Exposure, Urinary delta-Aminolevulinic Acid Concentrations and Haematological Parameters of Road Sweepers Working in Congested Areas of Bangkok

Road sweepers are especially exposed to environmental pollution. This study investigates the lead exposure, urinary delta-aminolevulinic acid concentration (ALA) and haematological parameters of road sweepers working in traffic-congested areas of Bangkok. One hundred and ninety-four apparently healthy road sweepers aged 20-59 years were investigated. One hundred and thirty-nine staff from an academic institution served as controls. Both male and female road sweepers had slightly, but significantly, lower mean corpuscular haemoglobin concentration (MCHC) values. The white blood cell count (WBC) in female road sweepers was significantly higher compared with the female controls. The proportion of reticulocytes was higher in male and female road sweepers compared with the controls, while no difference was found in blood lead levels and ALA between male road sweepers and controls. Female road sweepers had slightly higher blood lead levels compared with the controls. ALA was no different between both groups of ...

Mobilization of lead by calcium versenate and dimercaptosuccinate in the rat.

1. Calcium disodium ethylenediaminetetraacetate (CaNa2 EDTA) and meso-2,3-dimercaptosuccinic acid (DMSA) individually and in permutation-combination in various doses (0.1, 0.2 and 0.4 mmol/kg bodyweight) were investigated for their efficacy to mobilize lead from vital tissues into urine and faeces and to restore the lead-sensitive biochemical parameters in lead pre-exposed rats with a view to develop the most acceptable treatment regimen for lead poisoning with a minimal loss of endogenous essential elements. 2. The combined therapy was more effective than a single chelator treatment. 3. The combination of 0.2 mmol/kg CaNa2EDTA + 0.4 mmol/kg DMSA caused a lower depletion of zinc, calcium and iron but possessed almost equal capability to that of 0.4 mmol/kg CaNa2EDTA + 0.4 mmol/kg DMSA to produce urinary as well as faecal excretion of lead, to reduce the tissue burden of lead, including that of the brain, and to reverse lead-induced biochemical alterations. 4. The combination of 0.2 mmol/kg CaNa2EDTA + 0.4 mmol/kg DMSA has shown a definite improvement over previously reported combinations in terms of removal of lead from tissues, particularly the brain, restoration of urinary delta-aminolevulinic acid levels and a decrease in the loss of body zinc and is, therefore, recommended for the treatment of lead intoxication.

Variations in rat biochemical parameters after buckshot implant

Twenty eight albino Wistar rats were implanted with two 100 mg lead spheres: 14 received the implant in the peritoneum (P) and 14 in the thigh (T). Variations in the activity of delta-aminolevulinic dehydratase (ALAD), of urinary delta-aminolevulinic acid (ALAU), of hematoporphyrins (HP) and of lead blood levels (BPb) were then determined at 30, 60 and 90 days with respect to basal values. Parallel determinations were performed by the same schedule in 7 rats implanted with two glass beads and in 8 sham animals receiving surgical incision alone. Techniques employed for ALAD were Berlin and Schaller; for ALAU, Tomokuni and Ogata; for HP, Piomelli; and for BPb, atomic absorption spectrophotometry. As indicators of lead presence, HP and ALAU proved better, both in P and in T rats. The replacement of lead buckshot for small game hunting by other less toxic elements is recommended.

Trends of the biological monitoring measurements from 1991 to 1995

Partial amendments to the Japanese Regulation on the Prevention of Lead Poisoning and that of Organic Solvent Poisoning were made in 1989. As a result, the measurement of blood lead and urinary delta-aminolevulinic acid (delta-ALA) became indispensable items of the occupational health examination for workers who handle lead. Also, the measurement of urinary metabolites of workers who handle eight kinds of organic solvents (xylene, N,N-dimethylformamide, styrene, tetrachloroethylene, 1,1,1-trichloroethane, trichloroethylene, toluene, and normal-hexane) became mandatory. The results of the biological monitoring mentioned above are classified into one of three categories, that is, distribution 1, 2 and 3, according to the concentration of the determinants. In this paper, the incidence of distribution 1, 2 and 3 of each determinant is reported and its change from 1991 to 1995 is discussed. The incidence of distribution 3 was 0.1-5.0% in each determinant. Although the ratio of distribution 1, 2 and 3 seems to have been almost the same for 5 years some determinants decreased their percentage of distribution 3. It is important to utilize the biological monitoring results for the improvement of working environments and working styles, and health management.

Changes in certain hematological and physiological variables following single gallium arsenide exposure in rats.

Gallium arsenide (GaAs), a group III-VA intermetallic semiconductor, possesses superior electronic and optical properties and has a wide application in electronic industry. Exposure to GaAs in the semiconductor industries could be a possible occupational risk. The aim of the present study was to determine the dose-dependent effect of single oral exposure to GaAs (500, 1000, or 2000 mg/kg) on some biochemical variables in heme synthesis pathway and few selected physiological variables at d 1, 7, and 15 following administration. The results indicate that GaAs produced a significant effect on the activity of delta-aminolevulinic acid dehydratase (ALAD) in blood and heart (particularly at d 7) following exposure to 2000 mg/kg, whereas urinary delta-aminolevulinic acid (ALA) excretion was elevated only at d 7. No marked influence of GaAs on blood hemoglobin, zinc protoporphyrin, and packed cell volume was noticed. Blood glutathione (GSH) was significantly reduced at d 7, but remained unchanged at two other time intervals. On the other hand, heart GSH contents remained uninfluenced on GaAs exposure. Most of the physiological variables, viz. blood pressure, heart and respiration rate, and twitch response, remained unchanged, except for some minor alterations observed at d 7 and 15 following exposure to GaAs at a dose of 2000 mg/kg. Blood gallium concentration was not detectable in normal animals and rats exposed to 500 mg/kg GaAs. Blood arsenic concentration was, however, detectable even at the a lower dose level and increased in a dose-dependent manner. All these changes showed a recovery pattern at d 21, indicating that the alterations are reversible.

Influence of L-lysine and zinc administration during exposure to lead or lead and ethanol in rats.

Influence of lysine and zinc administration on the lead-sensitive biochemical parameters and the accumulation of lead during exposure to lead or lead and ethanol was investigated in rats. The lead exposure inhibited blood delta-aminolevulinic acid dehydratase (ALAD) activity, increased blood zinc protoporphyrin (ZPP), urinary delta-aminolevulinic acid (ALA), serum glutamic oxalacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), blood and tissue lead levels, and decreased blood and hepatic glutathione (GSH) contents. Some of these effects were enhanced on coexposure to ethanol. The simultaneous administration of lysine and zinc reduced tissue accumulation of lead and most of the lead-induced biochemical alterations irrespective of exposure to lead alone or lead and ethanol. The depletion of endogenous calcium and magnesium owing to lead or ethanol exposure was also prevented by co-administration of lysine and zinc.

Correlation between lead in plasma and other indicators of lead exposure among lead-exposed workers.

In order to clarify the bioavailability of lead in plasma (PbP), we performed a study on five workers in a Japanese factory manufacturing lead glass-based paints. Blood and urine samples were obtained over a period of 15 months, during which time the workers took it in turns to perform sifting work (with the highest level of lead exposure) for 1-month periods. A total of 75 sets of blood and urine samples were thus obtained. We determined whole blood lead (PbB), PbP, Urinary coproporphyrin (CPU), urinary delta-aminolevulinic acid (ALAU), urinary lead (PbU) and ALA in plasma (ALAP). In the 15 sets of samples obtained at the end of the period with a high level of lead exposure, PbP correlated significantly with ALAU, CPU, PbU and ALAP, but PbB correlated significantly only with PbU. In the 60 sets of samples obtained following a low level of lead exposure, correlation coefficients between the concentrations of PbP and of ALAU, CPU and PbU exceeded those between the concentrations of PbB and of ALAU, CPU and PbU. These findings indicate that PbP is a better dose indicator of lead biochemically available for heme synthesis and that PbU has a closer correlation with PbP than with PbB.

Effects of Exposure to Lead on Selected Biochemical and Haematological Variables

Blood and urine samples were taken from 34 persons occupationally exposed to lead and from 56 non-exposed control persons and blood lead and haemoglobin concentrations, red blood cell count, erythrocyte glutathione peroxidase (GSH-peroxidase) and acetylcholinesterase (AChE), and urinary delta-aminolevulinic acid were determined. Blood lead concentrations of the lead-exposed subjects were within the range of generally accepted as safe for occupationally-exposed adults in many countries (i.e. below 50 micrograms Pb/dl blood). Yet, significant dose-dependent elevations were found in erythrocyte GSH-peroxidase and urinary delta-aminolevulinic acid. The urinary delta-aminolevulinic acid concentration of lead-exposed smokers was significantly elevated over that of lead-exposed non-smokers. Smoking did not effect the urinary delta-aminolevulinic acid concentration of control persons. In addition, a statistically significantly lower red blood cell count was observed in the lead-exposed group. Our results indicate that the above described safety standard for blood lead concentrations in occupationally exposed adults, although generally accepted, needs revision.