Dose-response relationships for inorganic lead. I. Biochemical and haematological responses

The multifunctional protein PACS-1 is required for HDAC2- and HDAC3-dependent chromatin maturation and genomic stability

Phosphofurin acidic cluster sorting protein-1 (PACS-1) is a multifunctional membrane traffic regulator that plays important roles in organ homeostasis and disease. In this study, we elucidate a novel nuclear function for PACS-1 in maintaining chromosomal integrity. PACS-1 progressively accumulates in the nucleus during cell cycle progression, where it interacts with class I histone deacetylases 2 and 3 (HDAC2 and HDAC3) to regulate chromatin dynamics by maintaining the acetylation status of histones. PACS-1 knockdown results in the proteasome-mediated degradation of HDAC2 and HDAC3, compromised chromatin maturation, as indicated by elevated levels of histones H3K9 and H4K16 acetylation, and, consequently, increased replication stress-induced DNA damage and genomic instability.

Effect of estradiol on heme biosynthetic pathway in lead-poisoned rabbits

OBJECTIVES

To clarify the effect of the female hormone estradiol (Est) on heme biosynthesis in lead-poisoned rabbits, parameters indicating lead exposure, such as free erythrocyte protoporphyrin (FEP) level and δ-aminolevulinic acid dehydratase (ALA-D) activity, were determined.

METHODS

Twenty-six male Japanese white rabbits (body weight (BW), 3kg) were divided into four groups: I (control), II (Est), III (Pb), IV (Est+Pb). About 3 weeks after castration, Est (3 mg/kg of BW) was injected intramuscularly, and 2 weeks thereafter, lead (1.2 mg/kg of BW) was injected intravenously. After the initial injection of each of these substances, the same dose of each of these substances was injected once a week until the 9th week.

RESULTS

In groups III and IV, FEP level increased and ALA-D activity in the erythrocytes, bone marrow and liver decreased with an increase in lead concentration in blood. FEP level decreased significantly (p<0.01) in the 8th and 10th weeks after Est injection in group IV compared to with that in group III and was not elevated in group II compared with that in group I. ALA-D activity in the erythrocytes, bone marrow and liver increased significantly in group II compared with that in group I, whereas Ht and Hb levels decreased in group II compared with those in group I, and decreased in group IV compared with those in group III. The level of iron in plasma (Fe-P) was within the normal range during experiment.

CONCLUSIONS

In this study, Est did not increase FEP level. From the above results regarding FEP level and ALA-D activity, Est may prevent an increase in FEP level caused by lead. Ht and Hb levels, which are the parameters of anemia, decreased mainly as a result of Est exposure rather than lead exposure.

Elevation of Blood Lead Levels in Emergency Department Patients with Extra-articular Retained Missiles

BACKGROUND

Patients who survive gunshot wounds often have retained missiles. Unlike intra-articular retained missiles, extra-articular retained missiles (EARMs) are not routinely removed. Cases of lead toxicity from EARMs have been described. This study seeks to determine whether blood lead levels are elevated in emergency department patients with EARMs compared with matched controls, whether clinical symptoms of lead toxicity are more prevalent in patients with EARMs than in controls, and whether longer missile retention times or recent hypermetabolic conditions are associated with higher blood lead levels.

METHODS

One hundred twenty adults with EARMs and 120 age- and gender-matched controls with no history of gunshot wound were prospectively enrolled on presentation to a large urban emergency department. Whole blood lead (WBL), zinc protoporphyrin, and hemoglobin levels were obtained. Patients completed a questionnaire regarding time since gunshot injury; symptoms of lead toxicity; and occurrence within 30 days of any surgery, alcohol abuse, illicit drug abuse, diabetic ketoacidosis, hyperthyroidism, infection, fracture, pregnancy, or lactation.

RESULTS

Five EARM patients (4%) and no control patients (0%) had WBL greater than our threshold for medical follow-up (20 microg/dL). Mean WBL was 6.71 microg/dL (95% confidence interval [CI], 5.68-7.74 microg/dL) in EARM patients and 3.16 mug/dL (95% CI, 2.79-3.53 microg/dL) in controls. This difference was statistically significant when analyzed by matched pairs t test (p = 0.0001). There was no difference in the number of symptoms associated with lead toxicity that were noted by EARM patients versus controls (p = 0.377). Longer duration of missile retention was not associated with higher blood lead levels (r = 0.125, p = 0.172). Of the five hypermetabolic conditions analyzed, only fractures were associated with elevated blood lead levels (9.95 microg/dL [95% CI, 5.77-14.13 microg/dL] in EARM patients with fractures vs. 6.23 microg/dL [95% CI, 5.23-7.23 microg/dL] in EARM patients without fractures).

CONCLUSION

Patients with EARMs have significantly elevated blood lead levels compared with matched controls. The occurrence of a bony fracture within the past 30 days is associated with a higher lead level. In 96% of patients with EARMs, elevated lead levels were not clinically significant and did not change patient management.

Alteration of biochemical parameters related with exposure to lead in heavy alcohol drinkers

Blood lead levels (PbB), delta-ALA dehydratase activity (ALAD) and erythrocytic protoporphyrin (EPP) values were studied in heavy wine and spirit drinkers. Results were compared in both groups and with a control group (teetotalers). Results in all cases are expressed as arithmetic means +/- SD. PbB values found in the three groups were statistically different inter se: wine group, 195 +/- 82 microg l(-1); spirits group, 159 +/- 69 microg l(-1); teetotalers, 72 +/- 43 microg l(-1). ALAD was significantly lower in the drinker groups (wine 26.9 plus minus 11.4 U l(-1)and spirits 28.3 plus minus 11.6 U l(-1))vs the control group (48.3 plus minus 13.5 U l(-1)). Differences in EPP levels in the three groups were only significant between the teetotaler and the wine drinker groups. Our findings indicate that, in heavy drinkers (more than 2 liters of wine per day), not only are lead levels increased in the blood but there are also biochemical alterations that affect the heme biosynthetic pathway, which should be taken into account in treatment for alcoholics.

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.

Evaluation of delta-aminolaevulinic acid in blood of workers exposed to lead

Exposure-effect and exposure-response relation between exposure to lead and delta-aminolaevulinic acid concentration in blood (ALA-B) were examined in 238 male workers exposed to lead. Concentrations of ALA-B ranged from 26 to 352 micrograms/l and lead concentrations in blood (Pb-B) from 7.1 to 86.0 micrograms/dl. Concentrations of ALA-B correlated closely with concentrations of Pb-B (r = 0.74), and increased ALA-B concentration occurred at Pb-B concentrations of around 30 micrograms/dl. Exposure-response curves indicated that the 50 percentile response doses were roughly 30, 40, and 50 micrograms/dl Pb-B when cut off points of ALA-B were set at 50, 60, and 70 micrograms/l respectively. The sensitivity and specificity of measurements of ALA-B concentrations for health screening were sufficiently high when the health based exposure limits of lead were set at 30-50 micrograms/dl. Moreover, a pronounced increase in ALA-B concentrations occurred when the inhibition rate of erythrocyte ALA dehydratase exceeded 85%. These findings suggest that ALA-B is a useful indicator for assessing the early effects of exposure to lead on haem biosynthesis.

Clinical relevance of urinary delta-aminolevulinic acid/logarithm of creatinine ratio in screening for occupational lead exposure

Using receiver operating characteristics (ROC) analysis, the clinical relevance of urinary delta-aminolevulinic acid concentration adjusted to the logarithm of creatinine concentration (ALA/log.Cn) proved to be better than that of uncorrected ALA or ALA/Cn ratio for the detection of blood lead levels (Pb-B) exceeding 2.5, 3.0, or 3.5 mumol/l in 483 men occupationally exposed to lead. Ala/log.Cn yielded validities of 1.63, 1.75, and 1.79 at Pb-B levels 2.5, 3.0, and 3.5 mumol/l, respectively. The same values for ALA/Cn were 1.59, 1.70, 1.78 and for ALA 1.52, 1.65, 1.72, respectively. The simple adjustment to log. Cn makes urinary ALA determination more efficient in biological monitoring of the effect of occupational lead exposure.

A comparison of the effects of inorganic and alkyllead compounds on human erythrocytic delta-aminolevulinic acid dehydratase (ALAD) activity in vitro

A study comprising two experiments comparing the effects of the alkyllead compounds triethyllead acetate and tetraethyllead as well as an inorganic lead compound (Pb(NO3)2) on human erythrocytic delta-aminolevulinic acid dehydratase activity was undertaken. In Experiment 1, four human blood samples were pre-incubated for 0 min or 60 min with increasing concentrations (0-1000 microM) of triethyllead acetate, tetraethyllead and Pb(NO3)2, and the delta-aminolevulinic acid dehydratase activity was determined. There was no discernible inhibitory effect of tetraethyllead at any concentration, with or without pre-incubation. Pb(NO3)2 showed a distinct effect at an addition concentration of 1 microM, with a substantial inhibition only following pre-incubation. Triethyllead acetate showed no difference in effect with pre-incubation. In the second experiment, the activating effects of zinc chloride (60 microM) and dithiothreitol (20 mM) on delta-aminolevulinic acid dehydratase activity were examined on four human blood samples in the presence of varying concentrations of Pb(NO3)2 (0-50 microM) and triethyllead acetate (0-1000 microM). The addition of zinc chloride alone showed little effect on enzyme activity, while dithiothreitol alone caused a substantial activation of the enzyme at all lead concentrations. The addition of both zinc chloride and dithiothreitol caused an even greater activation of the enzyme. The data indicate that Pb(NO3)2 is a much more potent inhibitor of delta-aminolevulinic acid dehydratase activity than triethyllead acetate (Ki values of 0.77 microM versus 130.37 microM. respectively). The use of delta-aminolevulinic acid dehydratase activity as an indicator of exposure may be questionable in cases of alkyllead exposure. Possible causes for differences in the inhibition of delta-aminolevulinic acid dehydratase by these compounds is also discussed.

Reevaluation of urinary excretion of coproporphyrins in lead-exposed workers

Urinary concentrations of coproporphyrin I and III (CP I and III) were determined by high-performance liquid chromatography in 131 male workers exposed to lead, and the relationships between lead exposure and urinary coproporphyrins were reevaluated. CP I had a statistically significant correlation with lead in the blood (Pb-B), but it was not useful as an indicator of the effect of lead on heme metabolism. On the other hand, CP III had a good correlation with Pb-B and markedly increased when Pb-B levels exceeded 40 to 50 micrograms/100 ml. Both sensitivity and specificity were more than 80% when the health-based Pb-B limit and the screening level of CP III were fixed at 50 micrograms/100 ml and 50 micrograms/g creatinine, respectively. In conclusion, measurement of CP III is sufficiently sensitive and specific enough in practice for the early detection of health effects due to lead exposure in the same way as the measurement of delta-aminolevulinic acid in urine.

Health effects of air pollution due to automotive lead in Jakarta

Atmospheric lead and its health effects were surveyed in Jakarta, indonesia. Public transportation drivers of small tricycles in downtown Jakarta (exposed group) and farmers who lived in the suburbs of Jakarta (control group) were examined for biomedical effects of lead. Lead concentration in the air along the streets where the drivers work is 3.6 and 1.7 μg/m3with a traffic volume of 5, 148/hour and 1, 284/hour for one side during the day. In the suburbs of Jakarta it was 0.3 μg/m with a traffic volume of 40/hour. The driver group had double the lead concentration both in blood and urine, delta-amlnolevullnic acid (ALA) dehydrase activity decreased by 30%, and higher coproporphyrin excretion compared to the control group on average. The differences were statistically significant. Mean ALA concentration and haematocrit value showed no difference between the groups. An increased absorption of lead and effects of lead at enzyme level are so pronounced that a lead reducing programme of gasoline may be recommended.

Evaluation of a new specific analysis of urinary delta-aminolevulinic acid in man

A new specific method for urinary delta-aminolevulinic acid (ALA-U) measurement in man as a serial screening method for health control in occupational lead exposure was compared with a recommended, selective test (DAVIS method). The new test can be run fully automated, and the cost of material per sample is much lower than in the DAVIS method. ALA values obtained with this specific method were lower than those measured with the DAVIS method (= DAVIS values) in each case due to the elimination of interfering urinary compounds. In DAVIS values below the biological tolerance level (BAT-level) of 15 mg/l, the percentage of interfering compounds varied between 10 and 80%; above BAT level, these components represented about 20% of the total amount of ALA-U. A strong correlation can be demonstrated between specifically measured ALA values and the enzyme activity of ALA-dehydratase (ALA-D) in blood at lead levels (Pb-B) below 35 micrograms/dl (r = -0.768 for ALA-U/log ALA-D; n = 18).

Lead contact and poisoning in Barbados slaves: historical, chemical, and biological evidence

Lead contact and lead poisoning have received scant attention in discussions of early West Indian societies but are potentially important issues in considering the health and medical problems of blacks. Although our discussion focuses on Barbados, the West Indian historical literature strongly suggests that our general findings are applicable to other Caribbean areas and have implications for understanding some of the disabilities of early white populations as well. In this paper we also seek to illustrate how bioanthropological and chemical analyses of slave skeletal remains and historical data can complement one another in defining and investigating various dimensions of slave life.

Cytochrome P-450 system dependent depression of delta-aminolevulinic acid dehydratase activity by bromobenzene in rats

Male Wistar rats (200-230 g) were treated with bromobenzene in soybean oil intraperitoneally (i.p.) (4 mmol/kg) once a day for 1 or 2 days while control rats received soybean oil alone. delta-Aminolevulinic acid dehydratase (ALA-D) activity was depressed to 80% and 43% in bone marrow after 24 h and 48 h, respectively. ALA-D activity was also depressed significantly in the liver after the administration of bromobenzene while the activity in peripheral erythrocytes was not altered. After the administration of bromobenzene, the concentration of reduced non-protein sulfhydryls in liver was the lowest at 24 h and increased thereafter. No significant change was observed in the activity of delta-aminolevulinate synthase in liver. The decrease of ALA-D activity was also reproducible in vitro. The 105 000 g supernatant fractions of rat bone marrow lyzates as ALA-D source were incubated with liver microsomes prepared from rats treated with phenobarbital. ALA-D activity was decreased by bromobenzene but no decrease was observed when the microsomes were preincubated with CO to inhibit cytochrome P-450. The effect of bromobenzene on ALA-D purified from rat erythroid cells was studied in incubations containing a reconstituted cytochrome P-450 system prepared from rat liver. The decrease of ALA-D activity was proportional to both the incubation time and to the concentration of P-450 while no decrease was detected when P-450 was inhibited by CO before the incubation.

Multiple causes of anaemia amongst children living near a lead smelter in Brazil

A prevalence study of anaemia was carried out amongst children, aged one to nine years, living near a lead smelter in Santo Amaro City, Northeast Brazil. It was found that the variation in haemoglobin levels was significantly associated with malnutrition and with the interaction between malnutrition and iron deficiency, but not with lead poisoning, iron deficiency, or hookworm infection, having allowed for the effects of age, area of residence, family per capita income and race. The effect of the interaction between malnutrition and iron deficiency on haemoglobin levels was most prominent amongst children aged one year and amongst those living in the most deprived area. The lack of demonstrable interaction between lead poisoning and iron deficiency in the causation of anaemia amongst these children is discussed.

Inhibition of delta-aminolevulinic acid dehydratase by trichloroethylene

Male Wistar rats (8 animals/group; 180-200 g) were exposed continuously to trichloroethylene (TRI) for 48 or 240 h or methylchloroform (1,1, 1-trichloroethane: MC for 48 h at 50, 400 and 800 ppm. The inhibition of delta-aminolevulinic acid dehydratase (ALA-D) was examined in liver, blood and bone marrow of naive and phenobarbital pretreated animals exposed to TRI. A clear cut dose-effect relationship between the exposure concentration or duration of exposure and the inhibition of ALA-D activity was seen for rats exposed to TRI. In addition to this finding, significant interaction between TRI exposure and phenobarbital treatment was observed in the inhibition of ALA-D in liver and blood. MC did not produce inhibition. Trichloroacetic acid and trichloroethanol failed to inhibit the ALA-D activity in vitro. It seems that a metabolite(s) of TRI other than the above 2 substances may play a role in the inhibition of ALA-D. The inhibition of ALA-D (38% or 48% of the control in liver or in blood, respectively) observed after the 240 h exposure at 400 ppm to TRI was accompanied by the significant elevation of delta-aminolevulinic acid synthase (186% of the control) in liver and the increase in excretion of delta-aminolevulinic acid in urine (142% of the control). This occurred without an apparent weight loss, liver injury or hematological changes.

Health effects of low level occupational exposure to lead: the trail, British Columbia study

Blood lead (PbB) was measured in a sample of 245 lead smelter employees and their wives in Trail, B.C. and 144 controls in Nelson, B.C. Smelter workers were divided into three groups according to lead exposure: (1) directly-exposed, (2) indirectly-exposed, and (3) office workers. The average PbB values found (41, 33, and 16 micrograms/dl, respectively) reflected exposure level. In the highest exposure group, male smokers had significantly higher PbB concentrations than nonsmokers (44 vs. 37 micrograms/dl). For exposed males, average number of "days off work ill" increased with increasing PbB range and significant correlations were found between PbB values and five biologically plausible health symptoms. None of those symptoms planted to detect response bias correlated. Because of a 4-month strike, PbB values were measured in a sub-sample from each exposure group before and 1, 2, and 4 months after smelter operation resumed. Exposed workers' PbB levels stabilized after 1 month's operation.

Biomonitoring lead exposure with delta-aminolevulinate dehydratase (ALA-D) activity ratios

The occupational or environmental exposure of selected populations to lead, either alone or in combination with other metals, was monitored using ratios of the activity of the erythrocytic enzyme delta-aminolevulinate dehydratase. The results obtained have reaffirmed earlier findings that this test affords several significant advantages over the use of the enzyme's activity value measured at a set pH value and other types of activity ratios to assess lead exposure. Furthermore, the activity ratios' proven sensitivity, reliability, reproducibility, specificity and stability warrant that they be considered as viable alternatives to the more widely accepted diagnostic criteria of lead intoxication namely zinc protoporphyrin and lead levels in blood.

Relationships between three indicators of lead exposure in workers: blood lead, delta-aminolevulinic acid and free erythrocyte protoporphyrin

Whole blood lead (Pb-B), urinary delta-aminolevulinic acid (ALA-U) and free erythrocyte protoporphyrin (FEP) were measured in three groups of workers (n = 196) with different degrees of exposure to lead, and one group of men with no previous exposure to the metal (n = 48). Inter-group comparison showed a correlation of r = 0.73 between Pb-B and log of ALA-U, and r = 0.91 between Pb-B and log of FEP. ALA-U and FEP values rose sharply after Pb-B values reached 450-500 micrograms/l.

Occupational lead exposure of storage battery workers in Korea

Two hundred and thirty-four lead workers employed in a storage battery factory in Korea were examined for lead in blood (PbB) and urine (PbU). delta-aminolaevulinic acid in urine (ALAU), coproporphyrin in urine (CPU), and haemoglobin. The dose-response relationship between PbB and ALAU suggested that a PbB below 50-60 micrograms/dl is a proper practical limit of biological monitoring for lead workers. The inter-relationship between PbB and ALAU or PbU was better explained by a segmental straight function than by a curvilinear function. Inclusion of data from workers whose PbB was below 30-40 micrograms/dl, if they comprise a relatively large proportion of the whole, seems to have a role as a dummy effect on the overall regression function causing the curvilinear trend. At a given blood lead concentration, the ALAU of lead workers increased with an increase in the duration of exposure. This could be explained by the chronic effect of lead on haem precursors. Semi-quantitative measurement of CPU still played an important part in the screening of lead workers due to its simplicity, showing high sensitivity (97.8%) in detecting lead workers with PbB of 60 micrograms/dl or over.

The laboratory evaluation of microcytic red blood cells

Microcytic red blood cell states are common clinical problems in both adult and pediatric age groups. The recent widespread availability of electronic blood cell counters for performing routine blood counts has increased the detection of microcytic red blood cells. Physicians must workup both symptomatic and asymptomatic patients with microcytic red blood cells before they can initiate proper therapy and/or counseling. The purpose of this review is threefold: (1) to discuss the causes of microcytic red blood cells in terms of disorders of decreased heme production vs. disorders of decreased globin production, (2) to review the clinical laboratory tests useful in differentiating microcytic red blood cell states, and (3) to present a practical approach for the laboratory workup of microcytic red blood cells.

Arginase and kallikrein activities as biochemical indices of occupational exposure to lead

In a group of 60 workers occupationally exposed to lead the blood and urine lead concentrations, haematocrit, ALA-D and arginase activities, and urinary 5-aminolaevulinic acid (ALA) and coproporphyrin concentrations, and kallikrein activity were determined. Correlation coefficients of -0.78 and 0.77 for Pb-B/ALA and Pb-B/arginase were found respectively for lead concentrations above 40 microgram/dl blood, and 0.83, 0.76, 0.74, and -0.64 for Pb-U/ALA, Pb-U/Cp-U, Pb-U/kallikrein, and Pb.U/kallikrein, respectively. It seems that the increase in serum arginase activity may be indicative of liver damage while the decrease in kallikrein activity may indicate kidney damage in workers exposed to lead.

Chromosome and biochemical studies in women occupationally exposed to lead

Chromosome and biochemical studies were conducted for 18 healthy females occupationally exposed to lead in the manufacture of electrical storage batteries and in 12 comparable female controls. Biochemical indicators of dose (blood lead) and effect (erythrocyte protoporphyrin, delta-aminolevulinicacid dehydratase activity of red blood cells) were significantly different in the two groups. Cytogenetic studies were performed on lymphocytes cultured for 2 and 3 days with phytohemagglutinin to investigate the possible effect of culture time with respect to yield of chromosome aberrations. The results showed significantly increased rates of metaphases with chromatid and chromosome aberrations--excluding gaps--in the exposed vs. controls at both culture times. The yield of abnormal metaphases was higher in the 3-day than in the 2-day cultures, both in the exposed and controls; the difference was moderately significant for controls, while highly significant for those exposed. These results demonstrate the occurrence of increased numbers of abnormal metaphases also in women occupationally exposed to lead, as previously found in males.

The action of small doses of lead on erythrocyte D-aminolevulinic acid dehydratase in the mouse

After a single intraperitoneal administration of lead in very small doses [1--100 micrograms Pbac/kg body weight (bw)], there was a dose-dependent, highly significant inhibition of erythrocyte D-aminolevulinic acid dehydratase (D-ALA-D) activity in mice. The maximal inhibition occurred between 3 and 24 h post injection (p.i.). After that, a rapid recovery of the D-ALA-D activity took place so that four days after lead administration, enzyme activity exceeded even the normal value. Only after eight days p.i. did the D-ALA-D value return to the initial level after a biphasic course. After 10 i.p. injections of 0.1 to 10 micrograms Pbac/kg bw, there was again a dose-dependent, highly significant inhibition of the erythrocyte D-ALA-D activity in mice. The maximal inhibition was shown to be 24 h after the last lead injection. In contrast to the single i.p. administration, however, we found a monophasic course for the return of D-ALA-D activity. The D-ALA-D values did not exceed the normal range at any time after 10 i.p. lead injections. Ten and 30 days oral administration of lead corresponding to i.p. doses exhibited similar results in D-ALA-D inhibition.

Lead and morbidity: A dose-response relationship

Many laboratory tests have been recommended for monitoring factory workers exposed to lead. To select the most useful test the best predictor of selected measures of morbidity was sought. 639 lead-exposed workers in several factories were questioned about abdominal ache, constipation, and fatigue and were examined for hand tremot. Packed-cell volume, blood-lead, urinary lead, and delta-aminolaevulinic acid were estimated in 489 workers. About half of the values for the latter three tests fell into the "excessive" or "dangerous" category of lead absorption. Blood-lead was a better predictor of morbidity than any other laboratory test, and further information did not add appreciably to morbidity prediction. The findings suggest that blood-lead measurement is the most meaningful test for monitoring workers exposed to lead. The effect of lead on morbidity does not appear to depend on its action on the porphyrin metabolic pathway.

Lead effects among secondary lead smelter workers with blood lead levels below 80 microgram/100 ml

A subgroup of workers from a secondary lead smelter was defined to include those with blood lead levels not exceeding 80 microgram/100 ml and with no past history of elevated blood lead. Central nervous system symptoms (tiredness, sleeplessness, irritability, headache) were reported by 55% of the group and muscle and joint pain by 39%. Zinc protoporphyrin (ZPP) levels were elevated in 71% of cases. Low hemoglobin levels (less than 14 gm/100 ml) were found in more than a third of the workers. While BUN and creatinine were mostly in the normal range, there was nevertheless a correlation between ZPP and both BUN and creatinine. Reduced nerve-conduction velocities were present in 25% of the group; this was not significantly different from findings in a control group. The data indicate that a blood level of 80 microgram/100 ml is an inappropriate biological guide in the prevention of lead disease.

[Biochemical methods for the detection of lead poisoning (author's transl)]

After a short description of sources of lead poisoning a review is given of toxicity, absorption, storage and excretion of lead. Afterwards its biochemical affects--especially the influence on the biosynthesis of heme--are treated. Methods for diagnosis of lead poisoning resulting from these affects--determination of coproporphyrine and delta-aminolevulinic acid excretion in urine, erythrocyte delta-aminolevulinic acid dehydratase activity and erythrocyte protoporphyrin--are discussed in detail.

Impact of air pollution by lead on the heme biosynthetic pathway in school-age children

Blood-lead level (Pb-B), erythrocyte delta-aminolevulinic acid dehydratase (ALAD) activity, free erythrocyte porphyrin (FEP) concentration, delta-aminolevulinic acid concentration in urine (ALAU), hematocrit value, and hemoglobin concentration were compared for groups of children 10-13 years old from areas differently polluted by lead (rural area and lead smelter area). The biological responses of the children were also compared with those observed in adults similarly exposed to lead (Pb-B: 10-40 mug/100 ml). Compared with the rural children, children living less than 1 km from the smelter exhibited a significant increase of Pb-B and FEP, a significant inhibition of ALAD, and a slight positive correlation of ALAU with Pb-B; however, they showed no biological signs of anemia. In children living approximately 1.5 km from the smelter, there was still a significant increase of Pb-B and a concomitant inhibition of ALAD, but no change in FEP concentration. Comparison of the dose-response curves between Pb-B and FEP in adult males, adult females, and children indicates that the sensitivity to lead is in the order of children larger than or equal to women greater than men. Based on the FEP response, it is proposed that 25 mug Pb/100 ml blood be regarded as the maximum biologically allowable concentration of lead in blood of school-age children.