{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T09:31:13Z","timestamp":1790760673282,"version":"4.1.0"},"reference-count":38,"publisher":"BMJ","issue":"6963","license":[{"start":{"date-parts":[[1994,11,5]],"date-time":"1994-11-05T00:00:00Z","timestamp":783993600000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/www.bmj.com\/company\/legal-information\/terms-conditions\/legal-information\/tdm-licencepolicy"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["BMJ"],"accepted":{"date-parts":[[1994,8,9]]},"published-print":{"date-parts":[[1994,11,5]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>\n                    <jats:bold>Objective<\/jats:bold>\n                    : To quantify the magnitude of the relation between full scale IQ in children aged 5 or more and their body burden of lead.\n                  <\/jats:p>\n                  <jats:p>\n                    <jats:bold>Design<\/jats:bold>\n                    : A systematic review of 26 epidemiological studies since 1979: prospective studies of birth cohorts, cross sectional studies of blood lead, and cross sectional studies of tooth lead.\n                  <\/jats:p>\n                  <jats:p>\n                    <jats:bold>Setting<\/jats:bold>\n                    : General populations of children &gt;=5 years. Main outcome measures - For each study, the regression coefficient of IQ on lead, after adjustment for confounders when possible, was used to derive the estimated change in IQ for a specific doubling of either blood or tooth lead.\n                  <\/jats:p>\n                  <jats:p>\n                    <jats:bold>Results<\/jats:bold>\n                    : The five prospective studies with over 1100 children showed no association of cord blood lead or antenatal maternal blood lead with subsequent IQ. Blood lead at around age 2 had a small and significant inverse association with IQ, somewhat greater than that for mean blood lead over the preschool years. The 14 cross sectional studies of blood lead with 3499 children showed a significant inverse association overall, but showed more variation in their results and their ability to allow for confounders. The seven cross sectional studies of tooth lead with 2095 children were more consistent in finding an inverse association, although the estimated magnitude was somewhat smaller. Overall synthesis of this evidence, including a meta-analysis, indicates that a typical doubling of body lead burden (from 10 to 20 \u03bcg\/dl (0.48 to 0.97 \u03bcmol\/l) blood lead or from 5 to 10 \u03bcg\/g tooth lead) is associated with a mean deficit in full scale IQ of around 1-2 IQ points.\n                  <\/jats:p>\n                  <jats:p>\n                    <jats:bold>Conclusion<\/jats:bold>\n                    : While low level lead exposure may cause a small IQ deficit, other explanations need considering: are the published studies representative; is there inadequate allowance for confounders; are there selection biases in recruiting and following children; and do children of lower IQ adopt behaviour which makes them more prone to lead uptake (reverse causality)? Even if moderate increases in body lead burden adversely affect IQ, a threshold below which there is negligible influence cannot currently be determined. Because of these uncertainties, the degree of public health priority that should be devoted to detecting and reducing moderate increases in children's blood lead, compared with other important social detriments that impede children's development, needs careful consideration.\n                  <\/jats:p>","DOI":"10.1136\/bmj.309.6963.1189","type":"journal-article","created":{"date-parts":[[2011,10,27]],"date-time":"2011-10-27T19:31:19Z","timestamp":1319743879000},"page":"1189-1197","source":"Crossref","is-referenced-by-count":312,"title":["Environmental lead and children's intelligence: a systematic review of the epidemiological evidence"],"prefix":"10.1136","volume":"309","author":[{"given":"S J","family":"Pocock","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"M","family":"Smith","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"P","family":"Baghurst","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[1994,11,5]]},"reference":[{"key":"2025122312105677000_309.6963.1189.1","doi-asserted-by":"publisher","DOI":"10.1056\/NEJM199210293271805"},{"key":"2025122312105677000_309.6963.1189.2","doi-asserted-by":"publisher","DOI":"10.1016\/0892-0362(93)90043-N"},{"key":"2025122312105677000_309.6963.1189.3","doi-asserted-by":"publisher","DOI":"10.1016\/0892-0362(89)90055-X"},{"key":"2025122312105677000_309.6963.1189.4","unstructured":"Cooney G Bell A Stavron C .Low level exposures to lead and neurobehavioural development: the Sydney study at seven years. In: Heavy metals in the environment. Edinburgh:CEP Consultants,1991:16-9."},{"key":"2025122312105677000_309.6963.1189.5","doi-asserted-by":"crossref","first-page":"855","DOI":"10.1542\/peds.90.6.855","article-title":"Low level lead exposure, intelligence and academic achievement: a long term follow-up study.","volume":"90","author":"Bellinger","year":"1992","journal-title":"Pediatrics"},{"key":"2025122312105677000_309.6963.1189.6","doi-asserted-by":"crossref","unstructured":"Hatzakis A Kokkeni A Maranelias C Katsouyanni K Salaminios F Kalandidi A .Psychometric intelligence deficits in lead-exposed children. In: Smith MA Grant LD Sora AI , eds. Lead exposure and child development. London:Kluwer,1989:211\u201323.","DOI":"10.1007\/978-94-009-0847-5_9"},{"key":"2025122312105677000_309.6963.1189.7","doi-asserted-by":"crossref","first-page":"1221","DOI":"10.1016\/S0140-6736(87)92683-3","article-title":"Influence of blood lead on the ability and attainment of children in Edinburgh.","volume":"i","author":"Fulton","year":"1987","journal-title":"Lancet"},{"key":"2025122312105677000_309.6963.1189.8","doi-asserted-by":"publisher","DOI":"10.1016\/0892-0362(90)90022-5"},{"key":"2025122312105677000_309.6963.1189.9","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1111\/j.1469-7610.1988.tb00687.x","article-title":"Blood lead, intelligence, reading attainment, and behaviour in eleven year old children in Dunedin, New Zealand.","volume":"29","author":"Silva","year":"1988","journal-title":"J Child Psychol Psychiatry"},{"key":"2025122312105677000_309.6963.1189.10","doi-asserted-by":"publisher","DOI":"10.1007\/BF00405790"},{"key":"2025122312105677000_309.6963.1189.11","doi-asserted-by":"crossref","first-page":"145","DOI":"10.1111\/j.2044-835X.1988.tb01089.x","article-title":"Relationship between blood lead, behaviour psychometric and neuropsychological test performance in young children.","volume":"6","author":"Harvey","year":"1988","journal-title":"British Journal of Developmental Psychology"},{"key":"2025122312105677000_309.6963.1189.12","first-page":"325","article-title":"Study of lead absorption and its effect on children's development.","volume":"2","author":"Wang","year":"1989","journal-title":"Biomed Environ Sci"},{"key":"2025122312105677000_309.6963.1189.13","doi-asserted-by":"crossref","first-page":"567","DOI":"10.1111\/j.1469-8749.1981.tb02038.x","article-title":"The relationship between blood lead concentrations, intelligence and attainment in a school population: a pilot study.","volume":"23","author":"Yule","year":"1981","journal-title":"Dev Med Child Neurol"},{"key":"2025122312105677000_309.6963.1189.14","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1016\/0013-9351(85)90081-7","article-title":"Comparing the effects of perinatal and later childhood lead exposure on neuropsychological outcome.","volume":"38","author":"Winneke","year":"1985","journal-title":"Environ Res"},{"key":"2025122312105677000_309.6963.1189.15","doi-asserted-by":"publisher","DOI":"10.1111\/j.1469-7610.1988.tb00754.x"},{"key":"2025122312105677000_309.6963.1189.16","first-page":"1","article-title":"The effects of lead exposure on urban children: the Institute of Child Health\/Southampton Study.","volume":"47","author":"Smith","year":"1983","journal-title":"Dev Med Child Neurol"},{"key":"2025122312105677000_309.6963.1189.17","doi-asserted-by":"crossref","unstructured":"McMichael A Baghurst PA Vimpani GV Wigg NR Robertson EF Tong S .Tooth lead levels and IQ in school-age children. Am J Epidemiol 1994 (in press).","DOI":"10.1093\/oxfordjournals.aje.a117275"},{"key":"2025122312105677000_309.6963.1189.18","first-page":"68","article-title":"Blood lead, tooth lead and child development in Edinburgh.","volume-title":"Heavy metals in environment.","volume":"Vol 2.","author":"Fulton","year":"1989"},{"key":"2025122312105677000_309.6963.1189.19","doi-asserted-by":"crossref","first-page":"689","DOI":"10.1056\/NEJM197903293001301","article-title":"Deficits in psychologic and classroom performance of children with elevated dentine lead levels.","volume":"300","author":"Needleman","year":"1979","journal-title":"N Engl J Med"},{"key":"2025122312105677000_309.6963.1189.20","doi-asserted-by":"publisher","DOI":"10.1007\/BF00377755"},{"key":"2025122312105677000_309.6963.1189.21","doi-asserted-by":"crossref","first-page":"181","DOI":"10.1111\/j.1469-8749.1989.tb03977.x","article-title":"Relationship between lead exposure indicators and neuropsychological performance in children.","volume":"31","author":"Bergomi","year":"1989","journal-title":"Dev Med Child Neurol"},{"key":"2025122312105677000_309.6963.1189.22","unstructured":"Environmental Protection Agency .Air quality criteria for lead. Research Triangle Park, CA:US EPA,1986:sec 12.4."},{"key":"2025122312105677000_309.6963.1189.23","unstructured":"MRC Advisory Group on Lead .The neuropsychological effects of lead in children: a review of the research. 1984-88. London:Medical Research Council,1988."},{"key":"2025122312105677000_309.6963.1189.24","doi-asserted-by":"crossref","first-page":"31","DOI":"10.2307\/2987502","article-title":"Environmental lead and children's intelligence: a review of recent epidemiological studies.","volume":"35","author":"Pocock","year":"1985","journal-title":"Statistician"},{"key":"2025122312105677000_309.6963.1189.25","doi-asserted-by":"publisher","DOI":"10.1146\/annurev.pu.12.050191.000551"},{"key":"2025122312105677000_309.6963.1189.26","doi-asserted-by":"crossref","unstructured":"Smith MA .The effects of low level lead exposure on children. In: Smith MA Grant LD Sors IA , eds. Lead exposure and child development. London:Kluwer,1989:3\u201347.","DOI":"10.1007\/978-94-009-0847-5_1"},{"key":"2025122312105677000_309.6963.1189.27","doi-asserted-by":"crossref","unstructured":"Grant LD Davis JM .Effects of low level lead exposure on paediatric neurobehavioural development: current findings and future directions. In: Smith MA Grant LD Sors IA , eds. Lead exposure and child development. London:Kluwer,1989:49\u2013115.","DOI":"10.1007\/978-94-009-0847-5_2"},{"key":"2025122312105677000_309.6963.1189.28","doi-asserted-by":"publisher","DOI":"10.1001\/jama.1990.03440050067035"},{"key":"2025122312105677000_309.6963.1189.29","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1006\/enrs.1994.1020","article-title":"Low level lead exposure and children's IQ: a meta-analysis and search for a threshold.","volume":"65","author":"Schwartz","year":"1994","journal-title":"Environ Res"},{"key":"2025122312105677000_309.6963.1189.30","doi-asserted-by":"publisher","DOI":"10.1037\/\/0012-1649.15.2.225"},{"key":"2025122312105677000_309.6963.1189.31","doi-asserted-by":"crossref","first-page":"437","DOI":"10.1080\/15287398609530941","article-title":"Lead concentration in deciduous teeth: variation related to tooth type and analytical technique.","volume":"19","author":"Grandjean","year":"1986","journal-title":"J Toxicol Environ Health"},{"key":"2025122312105677000_309.6963.1189.32","first-page":"235","article-title":"Home observation for measurement of the environment: a revision of the preschool scale.","volume":"84","author":"Bradley","year":"1979","journal-title":"American Journal of Mental Deficiency"},{"key":"2025122312105677000_309.6963.1189.33","doi-asserted-by":"publisher","DOI":"10.1126\/science.701-a"},{"key":"2025122312105677000_309.6963.1189.34","doi-asserted-by":"publisher","DOI":"10.1093\/ije\/16.1.57"},{"key":"2025122312105677000_309.6963.1189.35","doi-asserted-by":"crossref","first-page":"1127","DOI":"10.1016\/0140-6736(91)91975-Z","article-title":"Can meta-analysis be trusted?","volume":"338","author":"Thompson","year":"1992","journal-title":"Lancet"},{"key":"2025122312105677000_309.6963.1189.36","doi-asserted-by":"publisher","DOI":"10.1016\/0140-6736(91)90201-Y"},{"key":"2025122312105677000_309.6963.1189.37","doi-asserted-by":"publisher","DOI":"10.1093\/ije\/18.1.180"},{"key":"2025122312105677000_309.6963.1189.38","doi-asserted-by":"crossref","first-page":"418","DOI":"10.1016\/0140-6736(93)93004-K","article-title":"Meta-analysis of the literature or of individual patient data: is there a difference?","volume":"341","author":"Stewart","year":"1993","journal-title":"Lancet"}],"container-title":["BMJ"],"original-title":[],"language":"en","link":[{"URL":"http:\/\/data.bmj.org\/tdm\/10.1136\/bmj.309.6963.1189","content-type":"unspecified","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/syndication.highwire.org\/content\/doi\/10.1136\/bmj.309.6963.1189","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,12,23]],"date-time":"2025-12-23T20:11:05Z","timestamp":1766520665000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.bmj.com\/lookup\/doi\/10.1136\/bmj.309.6963.1189"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1994,11,5]]},"references-count":38,"journal-issue":{"issue":"6963","published-online":{"date-parts":[[1994,11,5]]},"published-print":{"date-parts":[[1994,11,5]]}},"alternative-id":["10.1136\/bmj.309.6963.1189"],"URL":"https:\/\/doi.org\/10.1136\/bmj.309.6963.1189","relation":{},"ISSN":["0959-8138","1468-5833"],"issn-type":[{"value":"0959-8138","type":"print"},{"value":"1468-5833","type":"electronic"}],"subject":[],"published":{"date-parts":[[1994,11,5]]}}}