How does formal and informal industry contribute to lead exposure? A narrative review from Vietnam, Uruguay, and Malaysia

Introduction: Lead industries are one of the major sources of environmental pollution and can a ﬀ ect human through di ﬀ erent activities, including industrial processes, metal plating, mining, battery recycling, etc. Although di ﬀ erent studies have documented the various sources of lead exposure, studies highlighting di ﬀ erent types of industries as sources of environmental contamination are limited. Therefore, this narrative review aims to focus mainly on lead industries as signi ﬁ cant sources of environmental and human contamination. Content: Based on the keywords searched in bibliographic databases we found 44 relevant articles that provided information on lead present in soil, water, and blood or all components among participants living near high-risk areas. We presented three case scenarios to highlight how lead industries have a ﬀ ected the health of citizens in Vietnam, Uruguay, and Malaysia. Summary and Outlook: Factories conducting mining, e-waste processing, used lead-acid battery recycling, electronic repair, and toxic waste sites were the primary industries for lead exposure. Our study has shown lead exposure due to industrial activities in Vietnam, Uruguay, Malaysia and calls for attention to the gaps in strategic and epidemiologic e ﬀ orts to understand sources of environmental exposure to leadfully. Developing strategies and guidelines to regulate industrial activities, ﬁ nding alternatives to reduce lead toxicity and exposure, and empowering the public through various community awareness programs can play a crucial role in controlling exposure to lead.


Introduction Role of formal/informal industries and lead environmental contaminant
Lead has been widely distributed and mobilized globally since its discovery for various purposes such as industries (mining, battery manufacturing, recycling), paints, ceramics, water pipes, electronic wastes, and traditional medicines [1,2].It is one of the most recycled metals globally and has the highest end-of-life recycling rate of all commonly used metals [3].It has been estimated that approximately 85% of lead is utilized for the production of lead-acid batteries, a type of rechargeable electric battery that uses nearly pure lead alloy [4].These lead batteries are used in vehicles, photovoltaic solar installations, telecommunication systems for Disclaimer: Lesley Jayne Onyon and Marie-Noel Brune Drisse are staff members of the World Health Organization.The authors alone are responsible for the views expressed in this publication and they do not necessarily represent the decisions, policy, or views of the World Health Organization.
energy storage and are routinely used as power backups in countries with fluctuating electricity supply.Lead-acid battery manufacturing and recycling are carried out globally in formal and informal ways, making lead recycling one of the significant sources of environmental contamination and human exposure in several countries [5].
With rapid economic growth and the advancement of information technology, the use of electrical and electronic equipment has accelerated, consequently increasing e-waste [6].Exportation of e-waste for reuse and recycling is common in developed and developing countries [7].Formal e-recycling refers to ideally licensed facilities that process e-waste indoors following industrial hygiene, worker protection, and pollution control rules and regulations.In contrast, informal e-recycling refers to informal recycling operations with minimal safety protocols or no precautions [8].Informal waste recovery and recycling have been conducted in several developing countries, such as, Vietnam [9,10], China [11,12], India [13], Ghana [14], Senegal [15], which particularly receives numerous amounts of second-hand machines that are recycled mainly by the informal sectors.These informal sectors hire many workers to recycle waste at a limited salary, applying crude and pollutive recycling methods for the separation for reusable components and quick recovery of contained metals.These activities are usually carried out in the backyard of the houses, contaminating neighborhood and the environment, and pose substantial health risks [11,16].Unsafe handling and recycling of e-waste containing a large number of hazardous chemicals such as lead, cadmium, and mercury, as well as persistent organic pollutants, such as polychlorinated biphenyls (PCBs) and brominated flame retardants [17,18].Informal industries fail to provide proper rules and regulations on handling and processing of heavy metals such as lead.
In most industry sectors, lead exposure occurs during manufacture, construction, trade, transportation, and remediation.Informal cottage industries and associated industrial activities related to lead mining, including smelting of mineral ores, transportation, and dumping, also contaminate the environment and increase lead exposure to people living nearby communities and neighborhoods.While construction workers are exposed to lead during the renovation or demolition of old buildings that have been painted with lead paints, other industrial workers risk exposure during soldering, plumbing, and other work that involves lead metal or lead alloys [19].The lead particles or fumes released during multiple steps of these mentioned lead containing processes are attached to the clothes, hair, and skin of workers, which, if unwashed before returning home from the workplace, might become a source of exposure to families, children, and the entire community [15,20].The probability of lead exposure increases by several folds when an informal recycling process is followed, usually inside the home and/or nearby yards particularly if using the assistance of children in dismantling batteries and cleaning.As the recycling process can be conducted under poor safety conditions, with less awareness about lead toxicity, informal recycling has resulted in environmental contamination and human exposure [21,22].

Lead exposure and related issues
Several studies have highlighted the various sources of lead exposure; however, studies highlighting industries as sources of environmental contamination are limited.Therefore, our objective is to outline the formal and informal industries as significant sources of environmental contamination in this review.We have presented three case studies showing how lead exposure has affected the blood lead levels of people in different regions of the world, Vietnam, Uruguay, and Malaysia.While the lead exposure is a global issue, our aim is to highlight on how lead exposure has affected people in emerging industrial giant countries (Vietnam, Malaysia) and developed countries (Uruguay).Furthermore, there are differences in the industrial sources of lead pollution in these countries.While in Vietnam, informal and formal e-waste recycling, as well as lead acid battery recycling has been one of the major reasons for lead exposure, Malaysia has growing issues with lead processing/smelters.Uruguay has industries/factories surrounded by residential neighborhoods.
Vietnam has been one of the major countries to use lead-acid battery recycling since the 1980s.However, the lack of specific e-waste legislation and strict laws in e-waste collection, transportation, and treatment leads to informal e-waste recycling with the involvement of traditional craft villages [9].Similarly, in Uruguay, there are several industry sources that are associated with lead pollution, and most of them are surrounded by residential neighborhoods.Smelters, informal batteries, and e-waste recycling activities have created contaminated sites, landfills, or hotspot of industrial waste [23].While Malaysia has been established as the new industrialized market economy in Asia, studies have shown that approximately 60% of paint brands contain high lead levels, making lead paint the primary source of childhood lead exposure [24].In addition, the lead exposure due to the industrial market are increasing rapidly especially among children and pregnant women.Finally, brief information is provided on lead remediation and government measures to prevent and manage environmental contamination by industries.

Methods
A systematic search was conducted using PubMed and Web of Science electronic databases.The search was performed using the following terms in different databases: ("Lead," AND "Lead exposure," OR "acid batter*," OR "lead level," OR "blood lead level," OR "industr*," "mining," OR "environment contaminat*," OR "e-waste," OR "e-waste process*," OR "recycl*").We included any papers published before we started summarizing information which was in mid-February 2021 and the language was limited to English.The inclusion criteria were as follows: a) the study focused on lead, b) the study presented lead level results as their outcomes, and c) research conducted in Vietnam, Uruguay, and Malaysia.Only original papers were considered in the results.First, the authors independently selected the papers and reviewed the documents' selections for any inconsistencies.Then, the authors paired to screen the full-text reports and decide whether they met the inclusion criteria.Any concerns regarding the paper's eligibility were resolved through a meeting with all the authors.We complied with each paper's references included in the review and made additions whenever a new paper was found.Neither of the review authors was blinded to the journal titles, study authors, or institutions.The conducted research is not related to either human or animal use.

Results
Using the above search terms, 1,150 papers were retrieved, imported into Excel, and duplications (n=20) were removed.Unpublished papers such as papers not published in any journal, thesis manuscript, drafts were excluded (n=50).Nonopen access papers (n=50) which were not fully available were removed.Papers that did not talk about lead and presented lead level results as their outcomes (n=900) were removed.The breakdown was animal or in-vitro studies (n=625), and non-original papers (n=275).The retrieved papers were then screened for relevance based on their titles and abstracts.Out of 1,150 papers, only 130 had relevant abstract, were able to be sourced and had available full texts.Finally, the papers that measured lead levels in Vietnam, Uruguay, and Malaysia were selected for the results.Only 44 papers presented the lead levels and remaining papers did not meet the selection criteria and hence were not from three particular countries.Full information can be obtained in Figure 1.
Factories conducting mining, e-waste processing, used lead-acid battery recycling, electronic repair, and toxic waste sites were the primary industries for lead exposure.The majority of pollution is caused by mining, used lead-acid batteries, and electronic waste processing industries.Craft villages are another type of industry handling electronic waste processing in Vietnam.Three different cases were described in this review (Figure 2).

Vietnam
The first case, Vietnam, illustrates the exposure to lead in craft villages and lead-acid battery recycling sites.The Socialist Republic of Vietnam has been one of the major countries to carry out lead-acid battery recycling since the 1980s in Southeast Asia.In Vietnam, it was projected that over 70,000 tons of used lead-acid batteries (ULABs) would be reprocessed in 2015, which is nearly twice that of the 40,000 tons reprocessed in 2010 [20].E-waste generated in Vietnam originates from the disposal of electronic and electrical equipment, from industrial processes in electronic industries, and illegal importation of discarded appliances from overseas and dismantling and recycling sites [9].Vietnam produced 257 kt of e-waste in 2019, or 2.7 kg per capita.However, no data exists on how much e-waste is formally collected and recycled in Vietnam [25].The mountainous region of North Vietnam has several lead mines.The Cho Dien lead-zinc mine, located at Ban Thi Commune, Bac Kan Province, was one of Vietnam's biggest mines and has been mined for nearly a century [1].In Vietnam, lead is emitted during industrial production and construction, transportation, handicrafts, and improper waste management, and is linked to different health outcomes [26,27].In addition, improper e-waste disposal and recycling have resulted in environmental contamination and have become emerging health issues [28].
Figure 2A shows the craft villages and the used lead-acid battery processing sites in Vietnam.Craft villages are Vietnamese communities where households produce different goods such as textiles, construction materials, recycled metal, recycled electronic products, paper, and plastic [29].At least 30% of all households are engaged in craft and non-farming activities, contributing to 50% of the village's total income.Out of 1,450 craft villages in Vietnam, 228 are traditional villages with a long history and make unique and typical Vietnamese products.However, these craft villages have also caused heavy pollution and waste generation, leading to severe environmental deterioration [30].The country report showed that E-waste residue from the recycling process ranges from 5 to 30% of the volume of the actual electronic product depending on the type.E-waste recycling practices occur in approximately 90 of a total of 1,450 rural craft villages [30].These e-waste recycling practices have been causing significant amount of lead exposure among inhabitants and nearby communities.
Different studies have determined lead levels among exposed and unexposed groups and in various environmental components in Vietnam as presented in Table 1.The people of industrial sites such as Dong Mai, Ban Thi, Hai Phong recycle more than 1,000 tons of waste per year, including e-waste.In these craft villages, the main types of e-waste recycled are cathode ray tubes, computers, audio equipment, video cassette recorders, motorcycles, small domestic appliances, printed circuit boards, and plastics [31,32].Most of the processing activities include recovery of metals by manual dismantling, fractionation of metal and plastic, sorting of electric parts, and shredding plastic casings into chips for resale using simple manual methods at home or nearby fields.These recycling operations are family-based and take place in houses close to residential areas without personal protective equipment.The dismantling amount of e-waste in each household in Bui village is approximately 1-10 tons per month, while the whole Bui village is 40-50 tons per month on average [31].As these processes are conducted in nearby yards, lead particles accumulate in the soil, causing soil and water pollution and even contaminating agricultural products.In addition, inhaling lead particles generated by burning or ingestion of contaminated foods and water contributes to lead poisoning in people living in those sites.Health problems including high risk of renal dysfunction, lead poisoning, and multi-organ damage from lead exposure have been reported in areas near lead mines, smelters, and ULAB recycling plants, where diffusion of lead to the surrounding environment may endanger both workers and residents [33,34].
A study conducted in Bui village showed that children living in this craft village undertaking e-waste processing had increased DNA damage levels from other communities engaged in farming and small businesses, not in e-waste processing [28].It also showed parental engagement in e-waste processing, distance to the nearest e-waste processing area, processing e-waste at their own house, engaging e-waste processing, pregnancy, and breastfeeding while processing e-waste were significant factors that contributed to increased risk of health effects on children [28].Another study showed positive association between blood lead and homocysteine among workers exposed to lead [35].The level of δ aminolaevulinic acid level (delta-ALA) in urine was higher among the residents at the ULAB recycling site than in the areas without the ULAB recycling factory [32].The increased ALA concentration is associated with exposure to alcohol, lead, and other agents.Besides recycling workers, the BLL had exceeded 10 μg/dL in children and women of reproductive age, suggesting widespread lead contamination in the community [36].A similar study conducted in Nghia Lo indicated that children in battery recycling and smelting craft villages in Vietnam are co-exposed to toxic metals such as lead, arsenic, cadmium, manganese, and chromium [29].Environmental investigations have shown that surface soil lead is higher in transportation routes and areas near smelter or collection sites than in other areas (median 6,400-10,000 mg/kg) [38].Lead concentrations in the hair samples of 109 participants living near village smelting areas ranged from 5.5 to 687 mg/kg (84.2 mg/kg average) [40].These findings suggested avoiding building houses along the smelter's transportation routes, signifying those areas unfavorable for the dwelling.

Uruguay
The second case Uruguay discuss the exposure of people not engaged in factories or industries dealing with lead, mainly children.With rapid industrial development, several Latin American and Caribbean countries have suffered from lead bioaccumulation.Since 2004, Uruguay has banned lead in gasoline [42].Montevideo, the capital and largest city of Uruguay, has been home to formal and informal lead processing industries, battery factories, and informal battery and other e-waste recycling activities particularly burning cables to obtain copper [23,43,44].In the last decade the primary sources of lead exposure were metal parts storage, e-waste informal recycling activities and landfills contaminated soil in low-income neighborhoods and families [42].Recovering metals from e-waste, particularly burning cables to obtain copper, caused one in 4 cases of lead exposure treated at the pediatric environmental unit in Montevideo [45].In addition, Uruguay generates one of the highest amount of e-waste per capita in Latin America 10.5 kg per individual in 2019 [25,45].Figure 2B shows the study sites included in the Uruguay.
Several studies have been conducted on Uruguayan children as they live and play around areas closer to the ground where toxic substances often accumulate.The lead level of people including children in Uruguay is presented in Table 2. BLLs of children were relatively higher, and approximately 30% of the children exhibited BLLs above the recommended levels [46].A study conducted among 357 schoolers and their mothers showed a mean BLL of 4.2 μg/ dL among first-grade children, suggesting that high BLLs were associated with poor ability to inhibit inappropriate behaviors [44].A similar study conducted among 222 preschool children showed that the mean BLL was 9.0 mg/dL, and approximately 32.9% of children had levels >10 μg/dL [47].A study showed that 25% of children had BLLs >10 μg/dL and lead-painted surfaces were significant source associated with BLLs >10 μg/dL [48].A study screened blood lead and anemia among 244 children and found that preschoolers had relatively high hair lead levels, and maternal hair metals levels were the strongest predictor of metal concentrations in children's hair [49].A comparative study from 1994 to 2004 showed a decline in the BLL of children over 10 years [50].A study conducted to describe the BLLs of children exposed to lead during the e-waste recycling process in Montevideo showed BLLs of 9.19 μg/dL among children and adolescents, which was higher than the recommended level (5 μg/dL) [45].A study conducted to examine pattern of exposure to multiple metals including lead in preschool children did not find lower cognitive scores compared to the low metal exposure cluster [51].However, additional studies with larger samples are important to test for the association with low-level metal exposure and the neurobehavioral development of preschool children.
The La Teja poisoning episode in 2001 attracted worldwide attention when it showed high BLL in children living in Montevideo (20 μg/dL) [23].After the 'La Teja' incident, multidisciplinary approaches such as medical intervention, remediation, systematic surveillance screening programs showed positive outcomes on reducing lead levels [23].A report showed that Uruguay's strict laws and regulations effectively controlled lead contents in paints with low lead levels in samples, where the maximum permitted concentration was 600 ppm [56].The safe level of lead concentrations in drinking water are generally below 1 μg/dL [57].Studies have also shown that the mean lead level in water was 1.5 μg/dL, and the lead concentration exceeded 1.0 μg/dL in approximately 39% of the water samples tested in Montevideo [55].However, studies suggest the need for future health and environmental actions to investigate other sources of potential health risks as lead continues to contribute a significant disease burden for the population [53].

Malaysia
The recycling industries have become significant activities related to lead in Malaysia [58].Malaysia has shown an increasing trend in the production of electronic waste contributing up to 364 metric tons of e-waste in 2019, 11.1 kg pe capita [25].About 62% of Malaysian paint samples had more than 5,000 ppm of lead, and about 78% had 600 ppm or more [59] which would not be permitted to sell in countries with legally restrictive lead limits.
Figure 2C shows the study sites included in Malaysia.Several studies have shown high lead concentrations in participants residing in the Malaysian city area compared to those in rural and coastal areas [60,61].Lead level in urban areas was five times greater than that in rural areas suggesting high emissions from exhausted automobiles [62].The air lead concentration was higher in Kuala Lumpur than in other cities such as Kemaman and Setiu [62].Children's cognitive scores were influenced even at low BLL concentrations [63].A study has shown that δ-Aminolaevulinic acid (ALA) is higher in printing industry workers, bus drivers, petrol, and vehicle workshop workers signifying occupational exposure to lead [64].Studies conducted before unleaded gasoline was phased out, have shown increased BLLs among participants living in urban areas compared to rural regions [65,66].However, with the introduction of unleaded gasoline in the late 1990s, the source of lead exposure from gasoline combustion and air decreased, showing a lower concentration of BLLs among different urban participants [67][68][69].
Not only in the gasoline, several studies have shown the lead exposure in different areas including industries as presented in Table 3.An elevated level of lead concentration was observed in the participants' blood and hair living near the copper mining vicinity along with water, soil, and plants, suggesting possible contamination due to mining activities [70].A higher air lead concentration was BLL of all adults and children exceeded  μg/dL.The lead levels were significantly higher than those in reference sites.

- []
Improving human health outcomes with a low-cost intervention to reduce exposures from lead acid battery recycling: Dong mai, Vietnam

Dong mai Children= and soil=
Blood, soil The Dong mai mitigation project resulted in substantial decline in human and environmental lead levels.

- []
Lead contamination in surface soil on roads from used lead-acid battery recycling in Dong mai, northern Vietnam Dong mai NA Soil Transportation routes from the smelter site had the greatest concentration of surface soil lead.

- []
The impact of lead recycling activities to human health and environment in Dong mai craft village, Hung Yen, Vietnam observed in the place where workers were engaged in circuit board soldering process than in comparative group working in electronics [71].A study conducted in the electronic industry showed that the mean BLL of soldering workers (6.12 μg/dL) was higher than that of workers in administration section (4.63 μg/dL) [72].Lead exposure occurred in farmers as well, where the lead concentration in the finger nail sample was 6.61 (mg/g), signifying exposure through pesticides and fertilizers containing lead in different agricultural activities [73].A study conducted among workers in battery-manufacturing factories showed that about 74% of workers in small factories have BLLs above the reference level [74].
One study showed decreased BLLs from mother to infant, signifying that lead freely crosses the placental barrier from mother to fetus [77].Another study conducted using maternal and cord blood showed that maternal BLLs were not significantly high compared to their acute toxicity level [78].

Discussion
Figure 3 shows the BLLs of the participants included in the study from these three countries shown in Table 1, 2 and 3. A global report has shown the estimated number of children with BLL >5 μg/dL is increasing in several industrializing countries, including Vietnam (n=3,242,192), Uruguay (n=178,744), and Malaysia (n=56,949) [79].Moreover, the increase in children's BLL showed that children are being exposed to heavy metals through different sources, either from parents working at/nearby

- []
E-waste recycling sites E-waste informal recycling: An emerging source of lead exposure in South America

Blood
The average BLL of children and adolescent was higher than the recommended level.

- []
Others Determination of arsenic and lead level in blood of adults from coastal community in Melaka, Malaysia Melaka Adult= Blood The BLLs of respondents along the coastal area did not exceed the blood heavy metals reference levels.

- []
Blood lead concentration and working memory ability on Malay primary school children in urban and rural area, Malacca Melaka Children= Blood Urban children had higher BLL than rural children.

 []
Blood lead levels in Malaysian urban and rural pregnant women Kuala Langat Pregnant women rural () and urban () area

Blood
The range of blood lead levels in occupationally unexposed, adult populations varied from  to  mg/dL.

 []
Concentrations of lead in maternal blood, cord blood, and breast milk Kuala Lumpur Pregnant ladies=

Blood, breast milk
The mean lead concentration of umbilical cord blood was higher than the . umol/l observed during winter and . umol/l in summer.

- []
Source profiling of arsenic and heavy metals in the Selangor River basin and their maternal and cord blood levels in Selangor State, Malaysia Selangor Pregnant ladies= Blood, cord blood, water BLLs in mothers were not significantly high compared to their acute toxicity levels.

 []
lead-exposed areas, playing with soil containing lead coming from the industries, or ingestion of dust in suspension.Table 4 presents the concentrations of lead (mg/kg) in the soil samples.Vietnamese and Uruguayan studies have shown an increasing trend in soil lead concentration levels (Figure 3).Recent studies that have reported elevated BLLs in children living near smelting areas or ULAB recycling sites in Indonesia, the Philippines, China, Kenya, Mexico, Australia, and Armenia [80][81][82][83][84][85][86].
A study conducted in Senegal revealed that mass lead intoxication occurred among children through inhalation and ingestion of soil and dust heavily contaminated with lead due to formal and informal ULABs showing BLLs from 40 to 614 μg/dL with an average of 129.5 μg/dL [15].Moreover, children living in households with enamel paints showed elevated BLLs across Asia, Africa, and North America [24,37,[87][88][89].The situation is extreme in Kabwe town, Zambia, where 74.9% of the population had BLLs above 5 μg/dL, with an estimated population mean BLL of 11.9 μg/dL [90].

Occupational and environmental lead exposure
Lead exposure is common in various occupations and industries including traditional industries where lead exposure is severe [91].Many lead industry workers continue to be exposed to lead at levels which can cause BLLs to exceed population averages easily.Several studies have highlighted the occupational health of workers in the e-recycling industry [92,93].High lead levels were observed in the air around dismantling, desoldering areas, and near-automatic crushing and separation processes [92,93].
Lead and Yttrium's overexposure among workers engaged in fluorescent lamp recycling have been recorded at France's e-waste recycling facilities [94].Higher concentrations of PCBs were found in the air and dust in the e-waste recycling areas in China, suggesting the atmospheric release of contaminants to the environment from informal e-waste recycling facilities [95].Therefore, protective guidelines, regular BLL monitoring and medical removal criteria for workers with significant lead exposure should be implemented strictly to enhance lead workers' health and prevent occupational disease [96].

Lead remediation and BLL
Different effective regulations, remediation, intervention programs, and public awareness campaigns have resulted in reductions of lead emissions and exposure [97].Remediation is the removal of hazardous contaminants from soil, ground, and surface water, which provides a chance to reduce pollution and consequently pollution-related deaths [98,99].
The main aim of remediation is to protect human health, restore the environment, retain the social fabric of the community, and maintain the viability of the industry.This begins with the recognition from all affected parties that a hazard exists, and it might be multi-faceted [100].There are in-situ and ex-situ remediation techniques to amend heavy metal-contaminated sites through surface capping, encapsulation, landfilling, soil flushing and washing, electrokinetic extraction, stabilization, solidification, vitrification, phytoremediation, and bioremediation [101,102].Soil abatement consisted of removing the top 15 cm of soil and covering the exposed subsurface with geotextile fabric, 20 cm of soil, and ground cover [103].Three methods of exposure assessment are used to measure the effectiveness of lead remediation in lowering exposures.The first is an empirical measurement of biomarkers of exposure or early biochemical effects.The second is a predictive mathematical modeling approach, whereby inputs of measured environmental lead levels are employed to estimate a measure of exposure, a BLLs value.Finally, combinations of measurement and modeling data [104].Several factors, such as government and company policy, community relations, stakeholders, topography, population density, climate, and land use, all play crucial roles in evaluating the effectiveness of remediation strategies [100].
Several studies have shown the effectiveness of remediation in reducing soil lead concentration and BLLs in the population; however, this process requires sufficient time and effort from all, including communities.Studies suggest a greater decrease in BLLs after remediation for those with initial BLLs of 25 μg/dL or above than those with BLLs <20 μg/dL [105].Early identification of lead-poisoned children, timely investigation and abatement of hazards can reduce BLLs along with regular, systematic tests and future studies [52,106].Multilevel remediation interventions, such as soil capping, household cleaning, and community awareness programs can effectively reduce BLLs in children and soil lead concentrations in about 14 months [107].A remediation intervention in Brazil showed a nearly 50% reduction in BLLs among children about 18 months after abatement [108].Similarly, an intervention conducted in Vietnam to reduce the risk of residents living near ULAB recycling sites showed a 67% reduction in children's BLLs.The intervention included a series of institutional and low-cost engineering controls comprising of the capping of lead-contaminated surface soils, cleaning of home interiors, education campaigns, and building changing and bathing facilities at affected workplaces [37].

Measures that can be taken by governments to prevent and manage environmental contamination caused by formal and informal industries
A large amount of heavy metals, including lead, found in landfills come from e-waste.WHO has been developing several guidelines on lead prevention and has been advocating about the role of the health sector in chemical management that needs to be implemented and protection of public health [109].Following the Geneva Declaration, the WHO initiative on E-waste and Child Health was launched in 2013 with the aim to increase access to evidence, knowledge and awareness of the health impacts of e-waste, improve health sector capacity to manage and prevent risks, track progress and promote e-waste policies and improve proper monitoring of exposure to e-waste and the facilitation of interventions that protect the health of vulnerable groups [110].The United Nation (UN) E-waste coalition is a group of 10 UN agencies and other international organization that have come together to increase collaboration, build partnerships and provide strong support to Member States to address the e-waste challenge [111].United Nations Environment Program have been undertaking efforts to promote several plans and policies to control lead's environmental and health risks and form global alliance to eliminate lead paints [112,113].
For any individual with BLL ≥5 μg/dL, the lead source should be identified and appropriate action taken to reduce and terminate exposure [113].Strict regulations should be implemented to limit the non-essential use of lead in household and consumer products.The government should enact removing, remediating, or replacing of lead-contaminated soil in communities where lead contamination is high [114].The nationwide establishment and implementation of a BLL screening program in populations known or suspected of being at risk of lead exposure contributes to a better understanding of the range lead concentration in citizens [79].
The environment is embedded in each of the 17 integrated goals of Sustainable Development Goals (SDGs), with e-waste specifically linking to a number of them.Different SDGs such as, 3, 8, 11, and 12 have highlighted the need to tackle the destructive impacts of e-waste among different groups, especially children.Several World Health Assembly resolutions have focused on the role of health sector in reducing the release of hazardous substances including lead during informal e-waste recycling [109].Addressing the health impact of air pollution, improving health through safe and environmentally sound waste management, and the transformation needed to improve lives and well-being sustainably through health environments can play crucial role in addressing this issue.
Establishment of Center for Environmental Health units, referral centers for diagnosis and prevention of lead, establishing an epidemiologic database to track BLL across countries.Strict legislation regulating battery recycling has been carried in Uruguay, Chile, and Brazil, which has yielded positive results and should be implemented in other countries to provide effective and rapid screening [115][116][117].In addition, the production of small wearable electronic devices has rapidly increased in recent years.The rapid production of these small devices are posing another challenge to those trying to recycle and recover them.Therefore, a partnership among academia, electronic manufacturers, national and international stakeholders, and recyclers should be indispensable [8].
E-waste consists of toxic heavy metals including Lead.Although the 1989 Basel Convention, to which there are 188 parties prohibits the export of e-waste, it still permits e-waste export if it is intended for reuse [7].E-waste recycling should be conducted in a safe and standard environment following proper safety protocols.Although industry conditions have improved over time, many countries lack regulations and the enforcement capacity to reduce occupational and environmental lead exposure through sectors adequately.There should be alternate means to encourage improvements in the industry, such as certification programs based on specific occupational, environmental, and product stewardship standards verified with independent third-party audits.These environmental certifications can provide opportunities for industries to expand the market for their products, increase prices, and gain a competitive advantage [118].
Reductions in the use of lead in petrol, paint, plumbing, and food and managing formal and informal lead industries can effectively reduce BLL concentrations in many countries [110].Progress in making legally binding controls on lead in paint are uneven and less than half of countries have taken action to outlaw this discrete source of exposure [119].However, a significant amount of lead exposure still occurs in many countries through paints, toys, and improper e-waste recycling.ULABs that are improperly disposed of can corrode, releasing lead and sulfuric acid, which can be observed on the ground and contaminate groundwater.Therefore, it is necessary to promote pathways to recycle them properly, either metallurgical or chemically, with some pre-treatment processes rather than a manual method with no safety precautions [120].Management and remediation of lead hotspots and controlled regulation of recycling and smelting operations produce favorable results in the community [79].In order to protect people from contamination by industrial workers, the children and vulnerable members should be avoided entering or playing near smelting areas and mining sites.Workplace clothes and shoes should be left at work sites, and workers should adhere to strict safety measures, including hand hygiene, showering before leaving work sites, and removing work clothes before going home.In addition, citizens need to be empowered with education and participatory action research, triggering the need to properly reduce their exposure to lead.

Conclusion and recommendation
This review paper outlined how different formal and informal industries are contributing to lead exposure in the environment.The findings have shown how different types of industries including informal and cottage industries have impacted workers' health, as well as their family members and children.However, because of the discrepancies in the information available in different studies, we were unable to conduct further statistical or pooled data analysis in this paper.The reduction of exposure to hazardous chemicals is crucial for achieving the SDGs.With rapid industrialization, the environmental impacts associated with industries should be controlled by identifying the sources, regulating strict laws and regulations, and timely monitoring of ecological exposures activities.
However, there remain gaps in strategic and epidemiologic efforts to understand several countries' environmental exposure and public health.Epidemiologic research needs to be conducted to assess the association between lead industries and their impact on human health and environment.More researches are required to understand the effectiveness of interventions being carried out to reduce lead exposure in Vietnam, Uruguay and Malaysia.Furthermore, studies should be conducted to understand knowledge, attitudes and health behaviors of adults, workers and vulnerable population including pregnant women, children residing near lead industries.Early identification of populations with elevated BLL and timely remediation can provide maximum benefits.Implementing legal policies for informal industries and managing informal sectors policies can restrict children from playing around the workplace, separate the workplace and residence, and trigger occupational and environmental health regulations that prevent excessive exposure of lead to the public and the environment.Therefore, developing strategies and guidelines to regulate industrial activities, finding alternatives to reduce lead toxicity and exposure, and empowering the public through various community awareness programs can play a crucial role in controlling lead hazards.
Author contributions: M.N.B.D., L.J.O.conceived the ideas; K.P., A.I., H.F., and R.K. collected the data; K.P. analyzed the data; K.P. led the writing; and K.P., A.I., H.F., M.N.B.D., L.J.O., J.G., A.L., and R.K. reviewed and edited the manuscript.Competing interests: There is no conflict of interest to declare.The authors alone are responsible for the views expressed in this article and they do not necessarily represent the views, decisions, or policies of the institutions with which they are affiliated.Informed consent: Not applicable.Ethical approval: This study does not involve human participants therefore ethical clearance was not required for this study.

Figure 1 :
Figure 1: Flowchart of the literature search.

Figure 2 :
Figure 2: Sites in three different countries included in this study.(A): Craft villages and used lead acid-battery recycling sites in Vietnam; (B): Uruguayan sites in current study; (C): Different Malaysian sites included in the study.

Figure 3 :
Figure 3: Change in mean blood lead levels over years in population from Vietnam, Uruguay, and Malaysia.Years in this figure refer to the year of publication.

Table  :
Summary of papers showing lead levels in Vietnam.

Table  :
Summary of papers showing lead levels in Uruguay.

Table  :
(continued) BLLs exceeded in % of the children.Lead in tap water ranged from . to  ug/L (mean ) and exceeded in % of the samples.The median soil lead ranged from  to , ug/g and was highest in industrially polluted areas.

Table  :
Poudel et al.: Formal and informal industries and lead exposure Summary of papers showing lead levels in Malaysia.

Table  :
Lead concentration in soil samples from Vietnam and Uruguay.