A Systematic Review of Epidemiologic Evidences on Lead and Cancers, 2003 - 2019

Abstract

Background: While lead has known adverse health effects, the evidence for its carcinogenicity in human is limited. The National Toxicology Program (NTP) classified lead and lead compounds as reasonably anticipated to be human carcinogens in 2004. The International Agency for Research on Cancer (IARC) classified them as “probably carcinogenic” (group 2A) its 2006 assessment. Both classifications were based on limited evidence in humans and sufficient evidence in animals. Since then, epidemiologic studies have investigated the association of lead exposure and a variety of cancers. We aim to review recent epidemiologic evidence on the carcinogenicity of lead among studies that were published after the NTP and IARC assessments. Method: A systematic literature review was conducted to identify relevant papers based on key terms, ‘lead’ and ‘cancer’, using PubMed and restricting to articles from 2003 to present. Studies/publications were excluded if they were irrelevant to the aim of this review, were not epidemiologic in nature, did not report site-specific information, or contained major study design concerns that may bias the findings. Included studies were categorized based on the specific cancer sites, and the study findings were summarized by cancer site.Results and Conclusions: The keyword search identified 195 articles published between January 1, 2003 and January 31, 2020. After evaluation based on the exclusion criteria, 43 publications were selected for this review. A variety of specific cancer sites have been studied, including biliary tract (7 studies), brain and nerve (11 studies), breast (8 studies), digestive tract (12 studies), head and neck (5 studies), hematologic (7 studies), mesothelial (3 studies), reproductive (6 studies), respiratory (16 studies), skin (3 studies), thyroid (1 study), and urinary tract (16 studies). The results from these published epidemiologic studies will be reviewed and summarized with regards to the reported association between lead and cancer outcomes.