The problem of lead poisoning

Lead poisoning: case studies

Early clinical features of lead toxicity are non-specific and an occupational history is particularly valuable. Lead in the body comprises 2% in the blood (t1/2 35 days) and 95% in bone and dentine (t1/2 20-30 years). Blood lead may remain elevated for years after cessation from long exposure, due to redistribution from bone. Blood lead concentration is the most widely used marker for inorganic lead exposure. Zinc protoporphyrin (ZPP) concentration in blood usefully reflects lead exposure over the prior 3 months. Symptomatic patients with blood lead concentration >2.4 micromol l-1 (50 microg dl-1) or in any event >3.8 micromol l-1 (80 microg dl-1) should receive sodium calciumedetate i.v., followed by succimer by mouth for 19 days. Asymptomatic patients with blood lead concentration >2.4 micromol l-1 (50 microg dl-1) may be treated with succimer alone. Sodium calciumedetate should be given with dimercaprol to treat lead encephalopathy.

Efficacy of d-Penicillamine in Reducing Lead Concentrations in Children: A Prospective, Uncontrolled Study

Objective:

To evaluate the efficacy of oral d-penicillamine therapy in children with high blood lead concentrations.

Design:

A prospective, uncontrolled study.

Methods and Patients:

Seven children (2–16 y old; mean 8.7) with elevated blood lead concentrations but no symptoms of lead poisoning were treated with oral d-penicillamine. Lead-contaminated homemade flour as found to be the source of poisoning. Mean ± SD blood lead concentrations prior to therapy were 60.3 ± 12.9 μg/dL (range 47.8–83). Mean blood zinc protoporphyrin (ZPP) was 337.86 ± 58.55 μmol/mol hemoglobin (Hb) (range 247–394).

Results:

Ninety days of treatment with d-penicillamine lowered the mean blood lead concentration by 31.7% to a mean of 40.7 ± 8.6 μg/dL (range 30–53) and lowered mean ZPP blood concentrations by 40% to a mean of 201.14 ± 14 μmol/mol Hb (range 150–278). Three patients with blood lead concentrations >45 μg/mL at the end of this therapy were subsequently treated with succimer, an alternative oral chelator; the blood lead concentrations were further reduced to <45 μg/mL.

Conclusions:

d-Penicillamine therapy significantly reduced blood lead concentrations but did not achieve acceptable lead and ZPP concentrations for young children. Therefore, we conclude that 90 days of d-penicillamine treatment is of limited effectiveness in young children who have high blood lead concentrations and also show symptoms of lead poisoning.

Flour contamination as a source of lead intoxication

CASE REPORT

A 43-year-old man was hospitalized because of severe anemia and recurrent bouts of abdominal pain over 20 days. There was no known occupational exposure to toxins. Concomitantly, the patient's father complained of having the same symptoms. Familial lead poisoning was diagnosed when all 6 family members tested had high blood leads (31-64 micrograms/dL).

RESULTS

Following detailed examination of the potential sources common to all members of the household, the cause of poisoning was determined to be corn flour containing 38.7 mg/g lead. Physicians are reminded to consider lead poisoning in the differential diagnosis of individuals with unexplained symptoms, particularly those of abdominal discomfort and anemia.

Risk factors for high levels of lead in blood of schoolchildren in Mexico City

Risk factors associated with blood lead levels exceeding 15 microg/dl were analyzed in this report. This relatively high lead level was selected because, at the time the study commenced, it was considered to be a "safe" level. A total of 1583 schoolchildren were studied. The students were from (a) two areas in Mexico City (Tlalnepantla and Xalostoc) that have had historically high concentrations of lead in air, and (b) three areas (Pedregal, Iztalpalapa, and Centro) with less impressive air lead levels. Parents were presented with a questionnaire that solicited information about lead risk factors. A bivariate analysis and a multilogistic analysis were conducted to identify associations and to identify the model that most accurately explains the variability of the sample. High blood lead concentrations were found in children who lived in Xalostoc and Tlalnepantla (16.1 and 17.0 microg/dl, respectively), and the lowest concentration (i.e., 10 microg/dl) was found in children from Iztapalapa. The strongest association was with area of residence, followed by education level of parents, cooking of meals in glazed pottery, and chewing or sucking of yellow or other colored pencils. A child's area of residence is the most significant risk factor that must be accounted for when any study of lead and blood lead concentrations is undertaken. Follow-up in similar populations should assist greatly in the evaluation of the impact of governmental actions on public health.

[Motor neuron disease: metabolic evaluation]

The authors studied serum and urinary calcium and phosphorus levels, as well as abnormalities on the spine of 30 patients with motor neuron disease. The authors believe in multifactorial aspects in the pathogenesis of motor neuron disease, calling special attention to toxic and metabolic factors.

Lead poisoning in adults from renovation of an older home

Presented is the case of a group exposure to lead occurring during the removal of lead-based paint from an older home. One patient had symptoms from the time of exposure to the time of presentation, when he was acutely ill and encephalopathic. The patient was treated successfully with an initial course of British Anti-Lewisite agent and calcium disodium versenate (CaEDTA) chelation, and two subsequent chelations with CaE-DTA alone. The other two patients had elevated lead levels but were asymptomatic. They were followed closely, and their lead levels steadily declined over several months. The evaluation and treatment of lead poisoning and excessive lead levels in adults is discussed, as is the need for physicians and the lay public to become aware of the hazards of renovating older homes.

Low level lead exposure and neuropsychological functioning in blue collar males

To examine the interrelationships between normal aging, occupational lead exposure, and cognitive functioning, a comprehensive battery of neuropsychological tests was administered to 288 randomly-selected lead-exposed workers and 181 demographically-similar nonexposed controls. Contrary to previous reports, those workers with current blood-lead levels in the low to moderate range (less than 50 micrograms/dl) were found to perform as well as controls on measures of learning, memory, attention, visuospatial ability, and general intelligence. They differed from controls only on one measure of psychomotor speed and manual dexterity, the Grooved Pegboard Test, and these between-group differences were restricted to the older lead workers. It is likely that these results are secondary to lead-mediated neuromuscular damage. There is little support for the view that older adults with current blood lead levels in the low to moderate range are at risk for developing significant CNS dysfunction, even though they may have had a past history of excessively high blood lead levels.

Basophilic stippling of red blood cells: a nonspecific finding of multiple etiology

Basophilic stippling of red blood cells (BSC) has been noted in lead intoxication since 1899 and has been considered a classic laboratory sign of lead poisoning since that time. BSC are inclusions of aggregated ribosomes found only in the red blood cells and may be confused with siderotic (iron) granules. Heinz Bodies, or even reticulocytes. BSC are an inconstant finding in lead intoxication. In a review of peripheral blood smears from 1,000 consecutive internal medicine patients, we found BSC in 27%. These occurred in a variety of malignant, rheumatologic, hematologic, cardiovascular, and other diseases, frequently with an associated anemia. BSC may even be found in a small percentage of normal people; thus, it must be emphasized that BSC is a nonspecific finding. Furthermore, BSC has been replaced by blood lead (since the 1940s) and zinc protoporphyrin (since the 1970s) levels for biologic monitoring of lead-exposed workers.

Vulnerability to lead in protein-deprived suckling rats

Most studies on lead toxicity in the suckling rat have been performed with doses leading to growth retardation. In a previous paper ( Sundstr öm et al. 1983), the effects of different lead doses on normal suckling rats were described. The dose of 10 mg/kg body weight daily given on days 1-15 pp produced minute hemorrhagic lesions on day 15 in the cerebellum, whereas rats given 5 mg/kg body weight daily lacked microscopically discernible pathologic changes in the brain. None of these groups exhibited growth retardation. To further elucidate the association between lead encephalopathy and malnutrition, lead was administered to protein-deprived suckling rats. Protein deprivation was achieved by a diet with 50% reduction of protein content. The mothers of the pups were fed this diet from 2 weeks before conception throughout the experiment. Experimental animals were injected i.p. with 5 mg or 10 mg lead nitrate/kg b.wt. daily. Littermates, injected with vehicle without lead nitrate served as controls. Protein-deprived rats without either treatment were "external" controls. Animals were killed at 10, 15, and 20 days age for determination of lead content in blood and brain and for light-microscopic examination. The protein-deprived rats given 10 mg/kg b.wt. daily were growth-retarded as compared to unexposed protein-deprived rats. The mortality was almost 100% at 15-20 days pp. At 15 days, the cerebellum of these rats showed abundant hemorrhages, and the cerebrum was also hemorrhagically discolored. Protein-deprived rats given 5 mg/kg b.wt. daily did not differ significantly from unexposed protein-deprived rats with regard to body weight gain.(ABSTRACT TRUNCATED AT 250 WORDS)

The health effects of automobile exhaust. VI. Relationship of respiratory symptoms and pulmonary function in tunnel and turnpike workers

To examine the effect of automobile exhaust on respiratory symptoms and pulmonary function, the authors studied 175 tunnel and turnpike workers employed by the Massachusetts Turnpike Authority on two occasions 3 yr apart beginning in 1972. A standard respiratory symptom and illness questionnaire was administered, spirometry was performed, and proximal hair lead and blood lead content were measured as biologic indices of automobile exhaust exposure. One hundred nine (63%) workers were current cigarette smokers, 41 (23%) were exsmokers, and 24 (14%) had never smoked. Smoking was strongly related to respiratory symptoms of cough (P less than .001) and phlegm production (P less than .001), but not to wheezing (P = .41), breathlessness (P = .14), bronchial asthma (P = .13), or frequent chest colds (P = .14). When workers were stratified by smoking status, no effect could be seen between high automobile exhaust exposure as measured by a variety of parameters and all of the above respiratory symptoms and illnesses. The level of pulmonary function [forced expiratory volume in 1 sec (FEV1.0) and forced vital capacity (FVC)] was not related to past or current exhaust exposure in a cross-sectional analysis when we controlled for age, height, and cigarette consumption. In a prospective analysis of 84 of these workers, the observed changes in FEV1.0 and FVC over 3 yr were unrelated to exhaust exposure after controlling for age, height, cigarette consumption, and initial level of pulmonary function.

Cigarette smoking and lead levels in occupationally exposed lead workers

One hundred eleven workers at a secondary Pb smelter were surveyed to determine smoking and personal hygiene habits. Fifty-three percent of the smokers had blood Pb levels in excess of 60 micrograms/dl, compared to 31% of nonsmokers (p = 0.02). Among smokers, 66% of "heavy" smokers (greater than or equal to 1 pack a day) had blood Pb levels over 60 micrograms/dl, compared to 39% of the "light" smokers (p = 0.05). Those who kept their cigarettes on their person had a higher proportion of blood Pb greater than 60 micrograms/dl than workers who kept their cigarettes elsewhere (63 versus 36%, respectively; p = 0.08). The difference in blood Pb levels between smokers and nonsmokers may be due in part to direct environmental contamination of cigarettes or impaired lung clearance mechanisms, and could be important in workers with already elevated blood Pb levels.

Influence of documented lead poisoning on environmental modification programs in Newark, New Jersey

Data from the Newark, New Jersey Childhood Lead Poisoning Program suggest that the major consequence of the program has been early intervention rather than the amelioration of environmental contamination. During 1975 to 1976, the authors investigated housing for 253 black and Hispanic children with blood levels over 60 microgram/100 ml. Of these, 115 had moved or had given incorrect addresses and were lost to follow-up, 22 were in the same homes but did not make themselves available and in 16 instances, the houses were boarded up or had been destroyed by fire. Of the remaining 100 children, 31% suffered from symptoms potentially related to lead poisoning and 57% of the children were still living in the same dwelling in which the child was affected. Only one-fourth of the houses had been properly abated, i. e., the problem of environmental lead had been corrected, and one-fourth of the houses were not investigated at all by health authorities. These data support the concern that lead poisoning will not be effectively combated until the environmental issue is fully addressed.

Biochemistry and measurement of environmental lead intoxication

Lead is probably the oldest and most widely distributed environmental intoxicant, but unlike many of the synthetic agents which cause the greatest concern in industrial societies today, it occurs naturally at low levels in the environment and was present during evolutionary times. Galena (PbS), the most important lead-bearing mineral, is abundant and it is readily smelted. The metal is easily shaped and does not corrode and its compounds have found innumerable uses, particularly as pigments. This explains, in brief, why lead has had great economic importance since ancient times and why lead disease has plagued civilized societies for thousands of years and continues to be a serious concern to health authorities today. (Grandjean, 1975; Eisinger, 1977).

Lead and iron absorption from rat small intestine: the effect of dietary Fe deficiency

1. When lead is administered in drinking-water iron-deficient rats retain more Pb than Fe-replete rats (Six & Goyer, 1972; Klauder & Petering, 1975). In the present study the relationship between the absorption of Pb and Fe was investigated. 2. Adult male rats were transfered to a milk-based diet fed with or without supplementary Fe (180 mg Fe/kg as ferrous sulphate). After 7--9 d the absorption of duodenally-administered 203Pb and 59Fe was measured as uptake of radioactivity from the gastrointestinal tract after 90 min. 59Fe absorption was increased in rats given the unsupplemented diet for 7 d and was further increased in rats kept on the diet for up to 7 weeks. 203Pb absorption was not consistently increased by either short- or long-term Fe deprivation. 3. Much of the 203Pb in homogenates of the upper small intestine was bound to soluble protein of which up to 85% was dialysable. In contrast little 59Fe was dialysable. Only a small proportion of the soluble musosal Pb was associated with ferritin during gel-filtration chromatography although 203Pb precipitated together with carrier rat-liver ferritin with an antibody to rat-liver ferritin. 4. There appeared to be no direct relationship between the transfer of Fe and Pb across the small intestine of the adult rat.

Alterations in consummatory behavior of mice produced by dietary exposure to inorganic lead

Mice suckled by mothers given tap water and by mothers given a 5 mg/ml lead acetate solution during lactation were given a choice between tap water and a lead acetate solution after lactation. All offspring demonstrated an immediate aversion to the lead acetate solution. The offspring from the mothers receiving lead acetate during lactation demonstrated a greater aversion to the lead acetate solution than did the offspring from mothers receiving tap water. In addition, the lead acetate offspring drank more total fluid (tap water plus lead acetate solution) after weaning than the control offspring. The results indicate both learned and unlearned changes in motivation for fluid following ingestion of lead via the mother's milk in infancy.