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Today, health professionals are concerned about whether asymptomatic or mildly symptomatic increases in lead absorption in preschool children is one of the important factors causing minimal brain dysfunction, which only becomes evident later during the school years. This concern arises, in part, because current screening data show that 5 to 10% of the children tested recently in the United States have a degree of increase in lead absorption sufficient to cause metabolic derangement in heme synthesis, but insufficient, with rare exception, to cause classical acute clinical symptoms of plumbism. These screening data are disturbing because similar increases in lead absorption in suckling (but not older) experimental animals have been shown in some studies to be followed by the delayed appearance of subtle deficits in learning ability and aberrations in behavior. Derangement of hemoglobin synthesis is the first adverse effect of increased lead absorption now detectable. Intervention on the basis of the first or critical effect of a toxic agent before more serious effects occur has advantages from the viewpoint of preventive medicine. Current CDC guidelines for prevention of childhood lead poisoning are based on this concept and recommend the use of micro-scale erythrocyte protoporphyrin tests in conjunction with micro blood lead tests for early detection of children with disturbed heme synthesis caused by lead.

ABSTRACT Eighty-one percent of all hourly paid men who had been employed for more than six months in a factory making lead acid batteries and plastics completed a modified Cornell medical index health questionnaire. Blood lead and erythrocyte protoporphyrin (EPP) were also measured. The questions were grouped into symptom categories as follows: all physical, all psychological, “potentially lead induced,” pulmonary, cardiovascular, gastrointestinal, skin, nervous system, genitourinary, and fatigue. For each symptom category the pooled percentages of men whose symptom scores were above the common median of the three blood lead groups 10-, 40-, and 60 and over μg/100 ml (0·48-, 1·93-, and 2·90 and over μmol/l) within age/smoking subgroups were calculated. In every symptom category the percentages in the two lower blood lead groups differed little, but the percentages were consistently higher in men with blood concentration of 60 μg/100 ml (2·90 μmol/l) and over. Differences between a combined 10-59 μg/100 ml (0·48-2·85 μmol/l) blood lead group and the 60 and over μg/100 ml (≥2·90 μmol/l) group were statistically significant at the 0·01 level for “potentially lead induced” symptoms and at the 0·05 level for skin and psychological symptoms. Broadly similar results were obtained with four log10 EPP groups 0·6-, 1·5-, 1·7-, and ≥2·0, but differences did not reach statistical significance. There was no obvious explanation as to why symptoms that are not found in classic lead poisoning should be increased almost as much as those that are. It was thought that these results could be biased due to the men's knowledge of the symptoms associated with lead exposure, but the possibility that they may be partly due to lead absorption cannot be excluded.

A study of workers exposed to low levels of lead as impurities in aluminum (as low as 0.07%) shows a statistically significant difference in blood and urine lead levels as compared with a control group. In addition, alterations in precursors of heme were demonstrated as reflected in elevated levels of urinary delta-aminolevulinic acid and erythrocyte protoporphyrin IX. This study has implications for workers who are exposed to metals with low concentrations of lead (less than 1%) since this exposure tends to go unnoticed both by the workers, even when symptoms are present, and by physicians who ignore or discard signs of lead intoxication because they relate the occupational exposure of the workers to other metals, not directly to lead.

Iron status, haemoglobinopathies and malarial infection were assessed in a representative sample of 2,968 subjects living in three rural districts and two urban districts of South Benin. Iron deficiency, defined by two or more abnormal values in the 4 independent indicators of iron status used (transferrin saturation, erythrocyte protoporphyrin, serum ferritin and mean corpuscular volume) was present in 31% of subjects. Anaemia (according to WHO references values) was found in 73.6% of them. Fifty-two percent of anaemias were associated with biochemical evidence of iron deficiency. Prevalence of iron deficiency and iron-deficiency anaemia was higher in children and menstruating women. There was no difference between rural and urban groups, except for children 73–168 months old, in whom the prevalence was higher in the rural group. Sickle cell trait was present in 21% of subjects and Plasmodium falciparum trophozoites were found in the blood of 96.5% of subjects. The frequency of anaemia was not correlated with the degree of malarial infection nor to the type of haemoglobin.

In an effort to determine whether iron deficiency, in the absence of anemia (hemoglobin >11.0 g/dL), might produce alterations in behavioral development, four groups of nonanemic infants, 9 to 12 months of age, with varying degrees of iron deficiency were studied. Infants were classified as iron sufficient, iron depleted, or iron deficient based on measurements of serum ferritin concentration, erythrocyte protoporphyrin values, and the mean cell volume of erythrocytes. Subjects in each group were tested with the Bayley Mental Development Index, treated with parenteral iron, and retested seven days later. The administration of iron produced a significant increase in the Mental Development Index scores (+21.6 points) in the infants with iron deficiency but no significant change in the scores of infants with iron sufficiency (+6.2 points) or only iron depletion (+5.6 points). It is concluded that iron deficiency, even in the absence of anemia, results in biochemical alterations that impair behavior in infants.

To investigate the influence of polychlorinated biphenyls (PCB) on porphyrin metabolism, Wistar rats were orally administered KC-400. The mean value of liver/body weight ratio in normal rats was 3.86%, with a range of 3.44% to 5.22%. Their mean blood protoporphyrin level was 23.3 μg/dl packed cell volume (p.c.v.), with a range of 11.8 to 64.4 μg/dl p.c.v., and their mean liver protoporphyrin level was 0.17 μg/gm wet weight, with a range of 0.03 to 0.40 μg/gm wet weight. A feed containing KC-400 (140–160 ppm) was given for 2 to 20 weeks to 20 rats. The mean value of liver/body weight ratio was 5.00%, with a range of 3.80% to 6.16%. The mean erythrocyte protoporphyrin level was 47.4 μg/dl p.c.v., with a range of 19.7 to 83.2 μg/dl p.c.v., and the mean liver protoporphyrin level was 0.36 μg/gm wet weight, with a range of 0.04 to 0.67 μg/gm wet weight. The liver coproporphyrin level showed abnormalities in 2 of 20 rats fed the feed containing KC-400, with values of 0.71 and 9.89 μg/gm wet weight, respectively. After administration of KC-400 feed for 43 weeks, the mean value of blood coproporphyrin level rose to 32.1 μg/dl p.c.v., with a range of 11.4 to 54.6 μg/dl p.c.v. The mean erythrocyte protoporphyrin level was 74.3 μg/dl p.c.v., with a range of 49.5 to 102.1 μg/dl p.c.v. The mean liver coproporphyrin level was elevated to 5.15 μg/gm wet weight, with a range of 0.45 to 9.48 μg/gm wet weight, and the mean liver protoporphyrin level was 0.65 μg/gm wet weight, with a range of 0.43 to 9.88 μg/gm wet weight. Thus, there was an increase in both liver porphyrin and coproporphyrin following KC-400 feeding. Liver cells in the rats with abnormal porphyrin levels exhibited a red fluorescence. From these results, we can deduce that KC-400 may induce abnormalities in porphyrin metabolism, when it is fed orally for a long period of time. These abnormalities in porphyrin metabolism are limited to the liver only.

The erythrocyte protoporphyrin concentration in 63 patients suffering from chronic renal failure was estimated and found to be significantly decreased when compared to healthy subjects. There was a negative correlation between the decrease of the erythrocyte protoporphyrin and the blood urea and haematocrit. Following haemodialysis the concentration of erythrocyte protoporphyrin was reduced but not significantly so. It is proposed that uraemia or insufficiency of erythropoietin could affect erythroblasts and young red cells impairing haem synthesis.

Simultaneous blood lead (PbB), erythrocyte protoporphyrin (EP), and hematocrit measurements were made semiannually in 232 normal infants from 6 to 24 months of age. The PbB averaged 7 (SD = 5) and ranged from 0 to 64 micrograms/dl. The incidence of elevated EP, a marker for deranged heme synthesis, was unrelated to PbB at levels below 15 micrograms/dl but was fourfold greater among the infants with PbB above 15 micrograms/dl. This relationship persisted even after eliminating the 31 (4%) anemic (hematocrit less than 33%) samples. The confounding effects of iron deficiency are discussed.

The relationship between zinc protoporphyrin (ZPP) and total erythrocyte protoporphyrin, measured as "free" erythrocyte protoporphyrin (FEP), was determined in 194 adult subjects with different occupational and non-occupational lead exposures. Furthermore, the ZPP-FEP comparison was considered with respect to the dose-effect relationship of ZPP and FEP with blood lead (PbB) for males and females, respectively. Bilirubin (Bil.) interferences in ZPP analysis were taken into account. A very close and highly significant relationship (r = 0.962, P0.001) was established between ZPP and FEP values. A significant correlation (P0.001) between log ZPP or log FEP and PbB (males r = 0.767 and 0.718; females r = 0.525 and 0.405) was also found. It was established, by both in vitro and in vivo studies, that Bil. interferes with the ZPP fluorescence readings; the relationship between "false" positive ZPP concentrations and Bil. concentrations (in vitro r = 0.987, in vivo r = 0.903) was highly significant (P0.001). A small but highly significant (r = 0.948, P0.001) influence of increased carboxyhemoglobin (COHb) concentrations on the decrease in hematofluorometer ZPP readings, due to inadequate oxygenation of the blood, was found. The results obtained confirm the usefullness of ZPP determinations using hematofluorometers for surveillance of increased lead absorption but stress that the interfering effect of Bil., and to a lesser extent of COHb, cannot be ignored.

The behaviour of blood (PbB) and two biological indicators of effect: erythrocyte protoporphyrin (EP) and urinary aminolaevulinic acid (ALAU), were studied in subjects who had ceased working with inorganic lead for at least one year. The relationships between these indices and chelatable lead (PbU-EDTA) were also analysed. As a comparison, a group of subjects currently exposed to inorganic lead was studied. At a given PbU-EDTA level, the PbB values were significantly lower in the workers with past exposure than those found in currently exposed subjects. The relationship between EP and PbU-EDTA illustrates that, for corresponding levels of chelatable lead, the values of the erythrocyte metabolite are identical in the two groups. Considering the EP-PbB relationship, however, at a given PbB level the protoporphyrin values appear distinctly more altered in the subjects with past exposure. The relationship between ALAU and PbU-EDTA shows that, at a given PbU-EDTA level the urinary metabolite in past exposed subjects is distinctly lower than in currently exposed workers, while the relationship between ALAU and PbB shows that, at similar blood lead values, the ALAU levels are identical in both groups. On the basis of these results, it is concluded that in subjects with past exposure, erythrocyte protoporphyrin can be used in establishing the persistence and extent of an “active deposit” of lead in the organism, while PbB and ALAU are of very limited value.

In this study of 467 healthy term infants seen for routine 1-year health maintenance examination, we determined the influence of mild prior infection on the concentration of hemoglobin and other laboratory evidence of iron deficiency. In addition we studied the Hgb response in 261 infants randomized to receive a 3-month course of treatment with either iron or placebo. Infants who had had one or more clinic visits because of infection during the previous 3 months or who were reported as not being entirely well during the past month or who had an elevated sedimentation rate were more likely to have anemia or "low normal" Hgb, higher erythrocyte protoporphyrin and serum ferritin values, and lower serum iron concentration than infants who had been well. Hgb response greater than or equal to 1 gm/dl after iron treatment occurred more commonly in infants who had had prior visits because of infection. The results indicate that upper respiratory and other mild antecedent infections commonly predispose to iron deficiency (probably because of a decrease in iron absorption).

Each of 65 laboratories analyzed 10 whole-blood samples for erythrocyte protoporphyrin by one or more of several analytical procedures. These procedures were of two types: (a) extraction of protoporphyrin from the erythrocytes into ethyl acetate/acetic acid, re-extraction into hydrochloric acid, and fluorometric measurement; or (b) direct reading in a portable fluorometer (hematofluorometer), with no pretreatment of the blood sample. Interlaboratory correlation was generally poor, especially between laboratories using extraction procedures. Hematofluorometric results intercorrelated better, but they had a low bias as compared to the extraction approach. Nationwide standardization of the test is required to assure satisfactory interlaboratory performance and to identify laboratories whose results are sufficiently accurate to be used for interpretations according to guidelines set forth by the Center for Disease Control for erythrocyte protoporphyrin testing.

We describe the magnitude of analytic errors and the within-subject biological variations for laboratory tests that are used in the diagnosis of anemia and iron deficiency. For Hb, hematocrit, and red cell indices, coefficients of variation for analytic and biological variations are less than 4%. In general, higher coefficients of variation are characteristic of serum iron, iron-binding capacity, serum ferritin, and erythrocyte protoporphyrin. Particularly high analytic variations between different laboratories have been described for iron-binding capacity and the greatest biological variations have been noted for serum iron. An awareness of these sources of error is helpful in designing studies and in interpreting laboratory results.

Human protoporphyria with atypical features suggesting increased hepatic protoporphyrin synthesis was investigated in 2 patients. Analysis of the distribution of protoporphyrin among circulating erythrocytes of increasing age indicated that the erythrocyte porphyrin burden derived predominantly from erythroid sources in case 1, and from hepatic sources in case 2. Intravenous hematin was administered to both patients to assess any negative feedback effect on protoporphyrin synthesis. Erythrocyte, fecal and plasma porphyrin levels were measured serially during basal, treatment, and follow-up periods. In case 1, a significant (P less than 0.001) drop in both fecal and plasma levels accompanied hematin, while erythrocyte levels remained unchanged. Hematin produced no appreciable changes in porphyrin concentrations in case 2. Allergic vasculitis followed hematin use in both cases. Based on data of this study and on previous data, a model for protoporphyrin transport and clearance was developed in which the variable clinical and biochemical manifestations of human protoporphyria are related to the relative contributions of erythroid and hepatic sources to the abnormal protoporphyrin pools.

An increase in erythrocyte protoporphyrin (EP) is one of the most useful indicators of adverse biological response to lead exposure. A nonlinear mathematical model relating EP to blood lead concentration (PbB) was fitted to data in a sample of 1677 U.S. children (ages 2-6 years) in the Second National Health and Nutrition Examination Survey (NHANES II). Iron status was defined by percentage transferrin saturation (PTS). The dose-response curves for EP vs PbB increased systematically with decreasing PTS, largely due to decrease of a parameter proportional to red cell lead-holding capacity with decreasing PTS.

We describe a “high-pressure” liquid-chromatographic method for separating all the porphyrins in the heme biosynthetic pathway. The preliminary extraction and purification method is such that only erythrocyte porphyrins with fewer than five carboxyl groups, which includes protoporphyrin and the much smaller amount of coproporphyrin present, are measured. The porphyrins extracted from erythrocytes are chromatographically separated by use of a simple eluent system and fluorometrically detected.

Blood lead concentration and erythrocyte protoporphyrin (PROTO) levels were determined in workers with a occupational exposure to lead. The exposure time of the workers was from 3 to 18 years.n the lead workers, the concentration of blood lead was 32±13μg/100ml and the erythrocyte PROTO levels were 147±102μg/100ml RBC. On the other hand, the normal levels obtained from healthy men with no history of lead exposure were 10±3μg/100ml for the blood lead and 43±17μg/100ml RBC for the erythrocyte PROTO.In the lead-exposed workers, there were a significant positive correlation be-tween the logarithm of erythrocyte PROTO and blood lead levels (r=0.6263, P< 0.001). In addition, the equation of the regression line was as follows: Log10 PROTO=0.0127 Blood lead+1.6808From this investigation, it will be demonstrated that the measurement of ery-throcyte PROTO together with the test of δ-aminolevulinate dehydratase which had often been carried out is available for detecting the degree of lead absorption in workers occupationally exposed to lead.

The dimorphic blood picture in sideroblastic anemia suggests the coexistence of at least two types of erythrocyte, the populations with the smaller RBCs being responsible for the crucial abnormality, namely the impairment of iron incorporation into protoporphyrin. In a patient with sideroblastic anemia who subsequently developed acute myelocytic leukemia, we found a light and a heavy cell population to be morphologically different, the lighter cells showing a smaller MCV and lower MCH, a higher reticulocyte count, fluorocyte count and protoporphyrin content. Radioiron uptake and 51Cr survival were 3.5% and 8.2 days for the lighter fraction, 37% and 20 days for the heavier fraction. Thus, the impairment of iron incorporation, the high erythrocyte protoporphyrin content, and the reduced survival of red cells in this patient with sideroblastic anemia appeared to be largely confined to the red cell population with the smaller RBCs.

We measured the concentration of erythrocyte protoporphyrin in 43 blood samples by two fluorometric methods. In the indirect method, protoporphyrin was extracted from blood and the fluorescence of the free acid in the extract was determined with a filter-fluorometer. These results were compared with results of direct determination of protoporphyrin in the same samples. In the direct assay the fluorescence of protoporphyrin, present in blood as the zinc salt, was measured without extraction, with the use of a hematofluorometer. Comparison of the results of the direct and indirect methods showed an excellent correlation (r = 0.986), but the hematofluorometric values (y) were approximately 9% lower than the fluorometric values (y = 0.911x). The slope of the regression line (0.911) is likely to be different for each hematofluorometer-fluorometer combination. Therefore, hematofluorometric values can only be compared with fluorometric values if the slope of the regression line is known and is used as a correction factor.

Determination of erythrocyte protoporphyrin levels was performed in workers who are occupationally exposed to lead. The level of erythrocyte protoporphyrin was easily measured with microsamples of blood by utilizing a fluorescent assay. The log of erythrocyte protoporphyrin level was closely correlated to blood lead level (r = .72) in lead-exposed workers. The erythrocyte protoporphyrin test is especially useful in the detection of mild increases in blood lead concentration under conditions of occupational exposure.

We determined the frequency of presumptive iron deficiency and lead toxicity in 198 Utah migrant children, ages 9-72 months, during the summer of 1985. There were no confirmed cases of lead toxicity. Thirteen per cent of those tested and 30 per cent of the children ages 9-23 months were iron deficient. Hematocrit determinations accurately predicted iron deficiency in only 35 per cent of the children confirmed to have this disorder via erythrocyte protoporphyrin screening.

Bovine blood is used frequently as control material in interlaboratory comparisons for blood-lead analysis, but an erythrocyte protoporphyrin control material is needed. We present data on the rate of changes in blood lead and erythrocyte protoporphyrin in steers fed lead acetate. We also show, by comparison of fluorescence spectra with those of known compounds, that most of the porphyrin in lead-burdened steers probably exists as free protoporphyrin IX along with some zinc-complexed protoporphyrin IX. Bovine blood is suitable as an erythrocyte protoporphyrin control material for laboratories using acid extraction procedures, but not for the proficiency testing of laboratories using hematofluorometers.

Body iron stores in blood donors were assessed using front-face fluorometric assays of erythrocyte protoporphyrin/heme ratios. Comparison was made with hemoglobin levels and serum ferritin assays. Erythrocyte protoporphyrin/heme assays provide quick and reliable information about possible underlying iron deficiency in the absence of anemia, particularly in regular blood donors.

The activity of haem synthetase, the enzyme which chelates iron to protoporphyrin to form haem, was measured in cultured skin fibroblasts of children with protoporphyria and their parents from three families. In each family, one parent had deficient haem synthetase activity (3·0-11·1 pmol protohaem formed/mg protein/h) when compared to values in eight non-porphyric controls (mean 24·9, range 13·7-51·5). The level of activity in the three parents was similar to that in their affected children. In two families the parent with deficient activity was also thought to be the carrier of the abnormal gene, as judged from a history of photosensitivity and analysis of erythrocyte protoporphyrin concentrations, but in the third family the pattern of inheritance could not be determined from these criteria. The activity of δ-aminolaevulinic acid synthetase was normal in cultured fibroblasts from the protoporphyric children and their parents, excluding a generalised defect in haem-pathway enzymes. These results support the premise that deficient haem synthetase activity, inherited in an autosomal dominant pattern, is the primary defect in protoporphyria.

Erythrocyte protoporphyrin content is increased in several human and veterinary disorders in which heme synthesis is disrupted. The nature of the defect determines whether zinc protoporphyrin, unchelated (free) protoporphyrin, or both are present in the erythrocytes. Extraction of the protoporphyrin into acetone/water (80/20 by vol) is a simple, rapid technique by which each protoporphyrin species is delivered into solution without removing zinc from zinc protoporphyrin. The ratio of zinc protoporphyrin to total protoporphyrin concentration correlated significantly with the ratio of fluorescence emission intensities at the zinc protoporphyrin peak and at an isosbestic point. This concentration ratio may be used with a quantitative measure of total erythrocyte protoporphyrin to define the absolute zinc protoporphyrin and free protoporphyrin content of erythrocytes.

SUMMARY Free erythrocyte protoporphyrin was estimated in 166 Thoroughbred horses and the mean value was found to be 40 µg·/ 100 ml. packed cells. Significantly lower haemoglobin concentrations were found in 21 horses whose erythrocyte protoporphyrin concentration was 70 µg·/ 100 ml. packed cells or greater.

Exposure to toxic materials originating in the workplace has been recognized in families of workers in several industries. However, to date this problem has not been studied in the storage battery production industry. Twenty-seven one- to six-year-old children of 22 workers at a storage battery plant at high risk of exposure to lead oxide were compared with 32 one- to six-year-old children in 22 neighborhood control families for evidence of increased lead absorption. Workers' children had significantly higher blood lead (p less than 0.001) and erythrocyte protoporphyrin (p less than 0.003) values than control children. Household exposures to lead in paint and water were similar for the two groups, but workers' homes had significantly higher concentrations of lead in dust (p less than 0.001). It is postulated that lead is brought home on the skin, hair and clothing of the workers and that their children are ingesting or inhaling the lead in household dust. This is the first report of increased lead absorption in children of workers in this industry.

1. 1. Two new procedures are described for the quantitative assay of “free” and zinc-protoporphyrin in red blood cells. 2. 2. Major clinical findings have included the following: (i) An average of about 10% of the total erythrocyte protoporphyrin is “free” in normal humans, but about one-third or more is usually “free” in blood of normal cows, rats and rabbits, (ii) In addition to human and bovine protoporphyria, “free” protoporphyrin was increased in (a) genetic carriers (clinically normal) of bovine protoporphyria, (b) acute Pb poisoning, and (c) some patients undergoing dialysis, (iii) Significant amounts of zinc-coproporphyrin were found in the blood of several dialyzed patients and in some “normal” cows.

The accumulation of lead (Pb) and erythrocyte protoporphyrin (EP) in blood was studied in 11 rabbits. The rabbits were given a daily dose of 50 mg Pb as lead nitrate, dissolved in 100 mL of drinking water. Blood samples were drawn once a week from the ear lobes and assayed for Pb and EP. The Pb concentration increased sharply during the administration of Pb while the EP concentration rose slowly. When Pb was withdrawn its concentration fell immediately, whereas the EP concentration started decreasing only after two weeks and the decrease was slower. At the end of the experiment the rabbits were sacrificed and the Pb content of a number of organs determined. The largest accumulation of Pb was in bone, followed by kidney, liver, lung, spleen, brain and heart. The concentration of Pb in brain and heart was much lower than in the excretory organs - spleen, kidney and liver.

After lead poisoning was confirmed in nine adult males industrially exposed to lead dusts, therapy was instituted with oral penicillamine. Several laboratory examinations confirmed diagnosis, and also monitored the efficiency of penicillamine therapy. This study sought to investigate the usefulness of protoporphyrin determination in erythrocytes as a tool in diagnostic and therapy-evaluating studies. This determination seems to be a good clinical aid in diagnosis, but is a poor monitor to project eventual recovery of lead-poisoned patients in short-term studies.

Iron deficiency and lead toxicity both result in increased erythrocyte protoporphyrin. The purpose of this study was to determine the differences in EP concentration, according to age and sex, obtained in the 2nd National Health and Nutrition Examination Survey of the United States and to determine the extent to which EP differences might be related to iron deficiency or lead toxicity. The highest EP concentrations were found in infants and children. Among adults, women had higher EP values than men. Lead toxicity (blood lead greater than 30 micrograms/dl) and low serum iron concentration/total iron binding capacity (Fe/TIBC less than 16%), often in combination, were associated with elevated EP values in infants and children. In women, elevated EP concentration were related primarily to low Fe/TIBC values, whereas in men there was only a weak association with elevated blood lead concentration. Age/sex differences in EP values diminished markedly when the influences of lead toxicity and iron deficiency were excluded by the above criteria.

1. Analysis of reticulocytes for δ-aminolaevulinic acid synthase (AmLev synthase, EC 2.3.1.37) and haem synthase (EC 4.99.1.1) activity in 17 workers in pulp production with low-level hydrogen sulphide and methylmercaptan exposure showed decreased activities in eight and six cases respectively. 2. Erythrocyte protoporphyrin concentration was below the control range in seven cases. 3. Low AmLev synthase and haem synthase activities were found in one patient with hydrogen sulphide intoxication 1 week after the event. The activities had returned to the control levels 2 months later, though erythrocyte protoporphyrin remained abnormally low. 4. In vitro, hydrogen sulphide inhibited haem synthase with an apparent Kl of 3.4 mmol/l. Sulphide anion, on the other hand, inhibited AmLev synthase activity 85% at 10 mmol/l concentration. Thiosulphate anion inhibited AmLev synthase activity 18% (Kl 27 mmol/l) and haem synthase activity 43% at 10 mmol/l concentration. Selenite inhibited AmLev synthase (Kl 5.1 mmol/l) and haem synthase (Kl 9.0 mmol/l). 5. The assay of AmLev synthase and haem synthase could be a valuable addition to the assessment of workers' health in industries generating hydrogen sulphide or/and methylmercaptan, although the mechanism of the toxic effect remains speculative.

• Conventional screening tests (blood lead and erythrocyte protoporphyrin levels) may not accurately reflect the magnitude of lead storage in children with mild to moderate increases in lead absorption, as assessed by edetate disodium calcium testing. Children with blood lead levels higher than 30 μg/dL and erythrocyte protoporphyrin levels higher than 50 pg/dL warrant careful measurement of the size of chelatable, potentially toxic lead stores. Edetate disodium calcium testing provides a more precise basis for therapeutic decisions in a child with mild to moderate increases in lead absorption. ( Am J Dis Child 1982;136:312-315)

A survey of residents of a community surrounding a lead smelter has revealed an alarming incidence of elevated blood lead and erythrocyte protoporphyrin concentrations. In particular, children who were less than 3 yr of age were severely affected. Of those children tested in December, 1980, 35% had blood lead concentrations between 50-69 microgram/dl, while an additional 12% had concentrations greater than or equal to 70 microgram/dl, and are, therefore, at risk for severe neurological sequelae.

Multiple sources of Pb have been identified for human populations, but there is little agreement as to their relative significance. Marked regional geochemical anomalies in the distribution of Pb have been identified and, in one district, their impact on rural communities has been determined. The absorption of ingested Pb is modified by its chemical and physical form, by interaction with dietary minerals and lipids and by the nutritional status of the indi­ vidual. Studies on children of various ethnic groups have demonstrated differences in soft tissue Pb burdens which may in part have a nutritional basis. Erythrocyte protoporphyrin determinations suggest that metabolic disturbances attributable to Pb may occur at soft tissue burdens previously regarded as acceptable. The problem of defining an adverse health effect in relation to environmental sources of Pb is discussed

Although lead has no physiological function and is present in only negligible amounts in the blood of remote populations, it has become customary to accept the usual blood Pb level(s) (BPb) observed in industrialized society as "normal." Pb interferes with many biochemical systems, among them the heme biosynthetic pathway; this is reflected by an exponential increase in erythrocyte protoporphyrin concentration (EP) as PBb increases. The present study estimated the threshold PBb at which an increase of EP occurs in a population of urban children. In the 2,004 children studied, BPbs ranged from 2 to 98 micrograms/dl, with 1,852 having a BPb of less than or equal to 30 micrograms/dl, a value presently considered normal. Preliminary analysis suggested that an exponential increase in the concentration of EP occurred after a threshold BPb (apparently between 12 and 20 micrograms/dl) was reached. Precise definition of the threshold BPb for an increase of EP was next determined by two approaches: segmented line techniques and probit analysis. Whether the entire population was analyzed or only the subset of samples with "normal" BPb (less than or equal to 30 micrograms/dl), both methods yielded a threshold BPb of 15-18 micrograms/dl (average value, 16.5). These studies indicate that the heme synthetic pathway is affected by Pb at a level of exposure commonly observed in urban children, which is well below the limit that is presently too easily accepted as normal.

Measurement of erythrocyte-Zn-protoporphyrin with a haematofluorimeter on blood samples from eighty-four lead-exposed individuals has been compared with a fluorimetric determination of the extracted porphyrins. The results agreed well, and the interference from bilirubin and unchelated protoporphyrin was low. An exponential increase in erythrocyte protoporphyrin and a linear decrease in blood haemoglobin with increased blood lead was found in seventy-nine males with occupational lead exposure. The haematofluorimeter is recommended as a useful tool in screening for lead poisoning.

This study was designed to compare the effectiveness of laboratory tests for iron deficiency (mean corpuscular volume, erythrocyte protoporphyrin, transferrin saturation, and serum ferritin) in predicting hemoglobin response to iron therapy in infants found to have low Hgb concentrations. Screening for anemia was performed on capillary blood of 1,128 healthy 1-year-old infants of United States Air Force personnel. The 25% who had Hgb values less than 11.5 gm/dl were asked to return for tests on venous blood before therapy and again after three months of therapy. Of the 188 infants completing therapy, 66 (35%) had a rise in Hgb concentration greater than or equal to 1.0 gm/dl and were designated responders. None of the confirmatory tests on venous blood reliably distinguished responders from those who subsequently showed no response. By using any one of the tests in combination with a capillary Hgb value less than 11.5 gm/dl, more than half of the infants with an abnormal value responded. But well over half of the responders would have been missed if treatment had been restricted to infants with abnormal values. Neither changes in the criteria for normality nor combinations of tests substantially improved our ability to distinguish the two groups. Because of the difficulty in distinguishing responders from nonresponders with additional laboratory tests and because of the simplicity, low cost, and relative safety of iron therapy in infants, we favor an initial therapeutic trial of iron first for determining the cause of low Hgb values in similar high-risk populations. Further costly workup can then be reserved for the small number of infants who still have unexplained Hgb concentrations less than 11.0 gm/dl after a therapeutic trial.

To evaluate occupational exposures to lead in shipfitters cutting and riveting lead-painted iron plates aboard an iron-hulled sailing vessel, we conducted an environmental and medical survey. Lead exposures in seven personal (breathing zone) air samples ranged from 108 to 500 micrograms/m3 (mean 257 micrograms/m3); all were above the Occupational Safety and Health Administration (OSHA) standard of 50 micrograms/m3. In two short-term air samples obtained while exhaust ventilation was temporarily disconnected, mean lead exposure rose to 547 micrograms/m3. Blood lead levels in ten shipfitters ranged from 25 to 53 micrograms/dl (mean, 37.8 micrograms/dl); levels in three of these workers exceeded the upper normal limit of 40 micrograms/dl. Blood lead levels in shipfitters were significantly higher than in other shipyard workers (mean 10.0 micrograms/dl; p less than 0.001). Smoking shipfitters (mean, 47 micrograms/dl) had significantly higher lead levels than nonsmokers (mean, 32 micrograms/dl; p = 0.03). Lead levels in shipfitters who wore respirators were not lower than in those who wore no protective gear (p = 0.68). Four shipfitters had erythrocyte protoporphyrin (EP) concentrations above the adult upper normal limit of 50 micrograms/dl. A close correlation was found between blood lead and EP levels (r = 0.70). Prevalence of lead-related symptoms was no higher in shipfitters than in other workers. No cases of symptomatic lead poisoning were noted. These data indicate that serious occupational exposure to lead can occur in a relatively small boatyard.

Screening for lead poisoning can be performed by measuring either blood lead (PbB) or a haematological indicator such as erythrocyte protoporphyrin (EP). We have screened 902 infants and children aged from 3 months to 5 years amongst those attending three primary health care centres in AI Jahra governorate of Kuwait. Blood specimens were collected by finger prick on Guthrie filter paper and the dried blood samples were mailed to the Central Laboratory of the Children's Hospital, Buffalo, USA. One hundred and eighty-four (20 per cent) had an elevated EP (greater than 50 micrograms/dl). Of those 11 had values above 159 micrograms/dl; 140 children were further tested for blood lead levels (PbB) haemoglobin, mean cell volumes, and percentage of transferrin saturation; 41 had blood lead levels greater than 25 micrograms/dl which is the current definition of elevated blood lead levels. Two children (2 per cent) were in Class IV, 17 (15 per cent) and 16 (14 per cent) were in Class II and Class III, respectively. There was a significant correlation between EP and PbB (r = 0.686; P = less than 0.001). Of 72 children with elevated EP and normal PbB, 32 were anaemic (Hb less than 11 g/dl) and 20 had iron deficiency. The role of tribal practices using lead contaminated preparations and their contribution to elevated blood lead levels is discussed.

Erythrocyte protoporphyrin (EPP) concentration was determined in 87 children who presented at the Adeoyo General Hospital and the University Teaching Hospital (Ibadan, Nigeria) for various ailments. Presence or absence of anaemia was based on haemoglobin concentration. There was a significant difference (p less than 0.01) between the mean haemoglobin values of the severely anaemic, mildly anaemic and control children. There was no significant difference (p greater than 0.05) between the mean haematocrit, mean EPP and mean EPP:Hb ratio of the mildly anaemic and control groups, but corresponding values for the severely anaemic group differed significantly (p less than 0.001) from the values for the others. The increase in EPP was correlated with the decrease in Hb concentration (r = -0.8263, p less than 0.001), suggesting that iron deficiency was a major cause of severe anaemia. EPP alone or in combination with Hb is effective in identifying anaemic individuals, while Hb alone tends to over-estimate the occurrence of iron deficiency anaemia. EPP values above 100 micrograms/100 ml of erythrocytes identified severe anaemia.

Children with accidental ingestions exhibit excessive hand-to-mouth behavior. In a lead-burdened environment, hand-to-mouth behavior contributes to increased lead absorption. To test the hypothesis that accidental-ingestion patients experience greater lead absorption than other urban children, 95 children under 6 years of age with recent ingestions of nonlead-containing materials and a matched control group were compared. Ingestors had higher mean blood lead levels than controls (25.0 micrograms/dl versus 22.2 micrograms/dl, P = 0.036) and higher mean erythrocyte protoporphyrin levels (40.6 micrograms/dl versus 28.6 micrograms/dl, P = 0.006). Ingestion victims were more than three times as likely as controls to be classified as having increased lead absorption. Thumb-sucking was twice as common among ingestors as controls (37% versus 19%). These findings indicate that children with accidental ingestions are at greater risk of increased lead absorption than other urban children.

Data are presented for erythrocyte protoporphyrin (EP) concentrations determined by the direct reading tecnhique of Lamola et al. (1) Mean concentration of EP in children whose blood lead concentration was less than 30 mug/dl was 34.7 mug/dl whole blood +/- 13.4 (SD). Mean EP concentration in children with blood lead concentrations of 40-59 mug/dl was 80.0 mug/dl. It was 158 mug/dl. It was 158 mug/dl for children with blood lead concentrations greater than 59 mug/dl. All children in this last group had concordant values for Pb and EP on the first or second test.

The clinical, biochemical and photobiological characteristics of the photosensitivity disease, erythropoietic protoporphyria, are presented. Treatment of this disease with beta-carotene is also discussed.