lead poisoning in children

Lead poisoning in children, resulting mostly from ingestion of chips of lead-containing paint from walls and woodwork in old, dilapidated housing, remains a unique public health problem. Its etiology, pathogenesis, pathophysiology, and epidemiology are known. Practical methods are available for screening, diagnosis, prevention, and treatment. Yet each year lead poisoning continues to cause the deaths of many children and mental retardation or other neurological handicaps in many other children.

Health workers should be reminded, and the public informed, that lead poisoning is preventable. As is true with many other diseases, total prevention may be difficult to achieve, but significant reduction in the number and severity of lead poisoning cases can be expected from a well-planned program.

The following is an analysis of many facets of lead poisoning in children based on a review of the literature. A plan of approach to this health problem is suggested.

Size of the Problem

Lead poisoning in children is not an uncommon occurrence in the United States. Although slum areas in large old cities appear to have by far the greatest incidence, this problem is not necessarily restricted to the poor; it has been reported in children from economically and socially advantaged homes (29).

It is difficult if not impossible to assess the true incidence of lead poisoning in children. Obviously, in any community where overt lead poisoning associated with

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pica is reported, many unrecognized, subclinical cases must also exist. But while one cannot talk in terms of incidence rates, from the number of cases reported in several large cities one must conclude that this health problem is quite common in many areas.

In New York City, over 500 confirmed cases of lead poisoning in children were reported in 1964. This is excluding over 100 suspected cases that were being observed or investigated. Of 61,167 poisonings reported to the New York City Poison Control Center between 1955 and 1963, 3 percent or 1,704 were cases of lead poisoning (19). In Baltimore, during 1956-1964, there were 1,337 known cases of lead poisoning in children (32). In Chicago, during 1959– 1961, 429 cases of lead poisoning were reported to the board of health. They represented 4.7 percent of the cases of accidental poisoning reported in that period (9).

Since these reported cases merely represent a portion of the total extent of lead poisoning, perhaps the following survey data are a better indication of the actual prevalence of this problem in slum areas.

In Cleveland, a survey was conducted among 549 children aged 12-35 months living in areas of old, poorly maintained housing where flaking paint was frequently found. Of these children, 28 percent had an abnormal urine that might be indicative of increased exposure to lead, and 6.4 percent fulfilled the diagnostic criteria for lead poisoning. Of 105 children of similar socioeconomic background living in a new housing project, none had significant evidence of lead poisoning (17). In Baltimore, among 604 children aged 7-60 months who came from a low-income congested area where lead poisoning was known to have occurred, 333 had clinical or laboratory evidence or a history suggestive of increased exposure to lead. Of these 333, 148 had blood lead levels exceeding 0.05 mg./100 ml. (4). Survey of a suspected high incidence area in Chicago disclosed that out of 500 study patients,

7.9 percent had clinical or laboratory evidence compatible with the diagnosis of lead poisoning (9).

Consequences of Lead Poisoning

Mortality

In a 3-year period, 1959-1961, lead poisoning accounted for 4.7 percent of 9,853 cases of accidental poisoning in children reported to the Chicago Board of Health, but it was responsible for 79 percent of the total deaths due to accidental poisoning for the same period (9).

Between 1959 and 1963, 182 children were treated for acute lead encephalopathy at Cook County Children's Hospital. Over the 5-year period, despite the use of chelating agents and various techniques for reducing intracranial pressure, the case fatality rate remained essentially unchanged at the 25 percent level (except for one year when a higher fatality rate occurred, reportedly as a result of the bilateral craniectomies employed as part of the treatment that year) (15). In Cleveland, the mortality rate reported for lead poisoning from 1952 through 1958 was 30 percent (17). Coffin et al. recently reported a mortality of 4.5 percent in a group of 22 children with lead encephalopathy who were treated with a combination of BAL (British anti-lewisite) and CaEDTA (calcium disodium versenate) and measures to control cerebral edema (10).

Morbidity

For many of those who survive, the outlook remains grim. In Chicago, a study of 425 children who were fol

lowed for 6 months to 10 years after treatment for lead poisoning revealed that 39 percent had some kind of neurological sequelae. Among the 59 children in this group who had presented encephalopathic symptoms initially, 82 percent were left with handicaps: 54 percent had recurrent seizures, 38 percent were mentally retarded, 13 percent had cerebral palsy, and 6 percent were found to have optic atrophy. Some had multiple handicaps (30). Other sequelae reported in children who had lead encephalopathy include behavior problems, inadequate interpersonal relationships and inability to comprehend the abstract (5,28). Lead poisoning appears to be a cause of renal impairment, according to extensive epidemiological surveys conducted in Australia.

The exact incidence of lead poisoning as a cause of mental retardation is not known, but limited surveys of blood lead levels among mentally retarded children suggest that the incidence is probably not infrequent (3, 29, 37). On the other hand, it has been contended that mentally retarded children are more likely to have pica and therefore more likely to have lead poisoning (3).

Several followup studies have indicated impairment of intellectual ability in children who had lead poisoning. In the series of 425 children with lead poisoning reported from Chicago by Perlstein et al., mental retardation was found to be the most frequent sequela, occurring in 22 percent of the children. Among those who presented symptoms of lead encephalopathy initially, 38 percent of the children were found to be mentally retarded at the followup study, as mentioned above (30).

Similar results have been reported by other investigators. Byers and Lord followed 20 children who had relatively mild lead poisoning and were discharged from hospitals as recovered. They found that the IQ's of these children 3 to 12 years later ranged from 67-107, with a mean of 90. All but one of these children showed unsatis

factory progress in school because of specific intellectual defect (5, 6). Jenkins and Mellins studied 32 children who had severe lead poisoning (nearly all had evidence of encephalopathy) and found that 6 to 8 months later, their IQ's ranged from 35–115, with a mean of 74. The majority were severely retarded (23). Smith reported that five or more years after lead poisoning, a group of children who had lead encephalopathy had an average IQ of 80 (range 58-104), while those who had lead poisoning without encephalopathy had an average IQ of 87 (range 75–117); a group of controls who had pica without lead poisoning had an average IQ of 98 (33).

Epidemiology of Lead Poisoning

1. "High risk" areas for lead poisoning are almost synonymous with the slums, where old, deteriorating housing prevails. In these areas, accessibility to flaking paint and broken plaster, high incidence of pica, and lack of adequate parental supervision provide an optimum environment for lead poisoning (20).

2. Children between the ages of 1 and 6 years are the main victims; those between 1 and 3 years of age comprise approximately 85 percent of the cases, with the highest incidence at age 2 years (20, 28). Over 50 percent of all deaths from lead poisoning occur in 2-year-olds (19).

3. Childhood lead poisoning is significantly related to pica. In New York City it has been reported that over 30 percent of children who manifest pica have lead poisoning (19). Seventy to ninety percent of children with lead