Perspective on lead toxicity, a comparison between the United States and Iran

Lead is a bluish-grey heavy metal that is ubiquitous in the earth’s crust. All forms of lead, including the organic and inorganic forms, are potentially toxic. Lead’s desirable physical properties such as its low melting point and high malleability have led to its widespread industrial use for thousands of years. At the same time, lead has been implicated in mass poisonings throughout history and remains a pervasive environmental and occupational toxin worldwide [1,2]. Lead toxicity can present as a broad-spectrum of disease, ranging from subclinical exposure to life-threatening poisoning [1]. International organizations, such as the World Health Organization (WHO) and the International Programme on Chemical Safety have had systematic programs in place for over 35 years to mitigate lead poisoning worldwide. Government regulation and public health interventions have led to a significant decline in severe and symptomatic lead poisoning in the US; however, despite these efforts lead exposure remains a major health hazard.Environmental exposure to lead occurs via several sources and can impact the entire population; however, children are much more susceptible to its toxic effects. As such, the majority of US public health initiatives have focused on the reduction of pediatric lead exposure [3]. Symptomatic lead poisoning was first reported in the US in 1917 and became more commonly recognized during the mid-20th century. It was also during this time that chelation therapy for lead toxicity was being developed and refined [4]. The neurocognitive sequelae of lead exposure in symptomatic children was readily apparent, but it was not until the 1970s that the more subtle effects of subclinical exposure were noted [5]. Because of the profound neurocognitive effects of lead, the US Centers for Disease Control (CDC) made formal recommendations for lead screening in children as well as defined a “normal” blood lead level (BLL). The recommendations for the upper limit of blood le