Hazardous Substances in E-Waste
The composition of e-waste is incredibly miscellaneous. E-waste contains complex mixtures of potential environmental contaminants that are distinct from other forms of waste (Robinson, 2009). It contains more than 1,000 different substances that fall under "hazardous" and "nonhazardous" categories (Ministry of Environment and Forests, 2008). Due to the presence of a large number of hazardous substances including heavy metals (e.g., mercury, cadmium, lead, etc.), flame retardants (e.g., pentabromophenol, polybrominated diphenyl ethers [PBDEs], tetrabromobisphenol-A, etc.), and other substances, e-waste is generally considered hazardous, and if improperly managed, may pose significant environmental and health risks (Tsydenova & Bengtsson, 2011). Some potential contaminants in e-waste are so uncommon that little research has been conducted on their disposal consequences. Further, chemical composition of e-waste varies depending on the age and type of the discarded item as some new chemicals are introduced into electrical and electronic equipment (EEE) from time to time while other chemicals are restricted. For instance, e-waste composition is changing with technological development and pressure on manufacturers from regulators and nongovernmental organizations (NGOs) (Robinson, 2009). The replacement of cathode ray tube (CRT) monitors with liquid crystal displays (LCD) is a constructive advancement in this context as it reduces the concentration of lead in e-waste. LCD displays, however, contain the heavy metal mercury.
Furthermore, e-waste contains certain precious metals such as gold, silver, and copper. This provides incentives for recycling and makes e-waste economically significant. For instance, precious metal concentrations in printed circuit boards are more than tenfold higher than commercially mined minerals (Robinson, 2009). Platinum group metals are included in EEEs due to their high chemical stability and conductance of electricity (Robinson, 2009). Thus, a hidden treasure lies beneath the ever-growing mountain of e-waste. Some 820,000 tons of copper are included in the annual flow of e-waste (Robinson, 2009).
Health Hazards Related to E-Waste Treatment
E-waste treatment including simple recycling, burning, chemical digestion, and disposal practices exposes the workers and area residents to high levels of toxicity through mechanisms such as inhalation, contact with soil and dust, dermal exposure, and oral intake of contaminated locally produced food and drinking water. Unregulated recycling activities generate workplace and environmental contamination by a wide range of chemicals. Methods used for recycling of e-waste release toxic metals (such as lead) as well as persistent organic pollutants (POPs) into the environment (Wong et al., 2007). Inhalation and dust ingestion are suggested as particularly important routes of human exposure. An assessment of risk from dust ingestion conducted by Leung and co-authors (2008) revealed that ingestion of lead- and copper-contaminated dust may pose serious health risks to workers and local residents. For instance, for a printed circuit board recycling worker, the estimated oral average daily dose of lead exceeded the "safe" oral reference dose for lead by 50 times. Available evidence demonstrates that e-waste-related mixtures (EWMs) contain both chemicals present in EEE components and chemicals released during e-waste combustion (Frazzoli, Orisakwe, Dragone, & Mantovani, 2010). EWMs can enter living organisms, from food-producing animals to humans, through the gastrointestinal tract as well as lungs and skin (Frazzoli et al., 2010). Toxicants in EWMs are generally POPs. POPs are the substances that are resistant to biodegradation, have a strong tendency to bioaccumulate in the food chain, and are prone to long-range transport. It has been reported that POPs have the potential to transfer from one generation to another through breastfeeding (Frazzoli et al., 2010). Hence, it is a pollutant not only of significant concern for the current generation but also for their offspring.
Effects on Food Crops
Fu and co-authors (2008) carried out a study in Taizhou in southeast China, which is the biggest e-waste recycling area in Zhejiang Province. Taizhou is also an important agricultural area in Zhejiang Province, and rice serves as the major crop for the local people. The authors investigated the heavy metal contents in rice samples from a typical e-waste recycling area. Ten heavy metals including copper, cadmium, and lead were found in 13 polished rice and relevant hull samples. Six paddy soil samples were also investigated. The results showed that the agricultural soil in Taizhou was most severely contaminated by cadmium, followed by copper and mercury. Moreover, the concentration of heavy metals such as lead and cadmium in rice near e-waste recycling sites was higher than those from other areas. The authors hypothesized the probability of lead intake by the local inhabitants being higher than the limit prescribed by the World Health Organization.
Effects on Child Health
Liu and co-authors (2011) carried out a study aimed at evaluating the dose-dependent effects of lead exposure on temperament alterations in children from a primitive e-waste recycling area in Guiyu, China, and a control area Chendian, China. It is widely known that environmental exposure to pollutants results in accumulation of lead and other toxic substances in children. The results showed higher blood lead levels (BLLs) in Guiyu children. Primitive e-waste recycling may threaten the health of children by increasing BLLs and altering children's temperaments. This is because lead exposure produces a wide spectrum of health outcomes, most notably neurocognitive and behavioral deficits in response to pre- or postnatal exposures (Liu et al., 2011). Child exposure to lead has been related to irreversible decreases in intelligence. The authors suggested that it is necessary to make policy changes to restrict e-waste recycling to certain areas so that children's exposure to chemical toxicants can be limited.
Contamination of Food Chains by the Toxicants From E-Waste
EWMs may accumulate in agricultural lands and be available for uptake by grazing livestock. Persistent bioaccumulating pollutants are of top concern from the standpoint of food chain contamination (Frazzoli et al., 2010). In general, chemicals from EWMs have slow metabolic rates in animals and may bioaccumulate in tissues and be available in edible products, such as eggs and milk (Frazzoli et al., 2010). For instance, PBDEs are lipophilic, resulting in bioaccumulation in organisms and biomagnification in food chains (Robinson, 2009). Studies reported e-waste contaminants in breast milk. The reporting of e-waste toxicants in milk is a major concern as dairy animals have productive lives much longer than meat-producing animals. Hence, a greater chance exists for bioaccumulation. It is noteworthy, however, that bioaccumulation occurs also in the adipose tissue, liver, and fatty portion of meat (Robinson, 2009). Bioavailability and bioaccumulation factors in aquatic species for polychlorinated biphenyls (PCBs) and PBDEs from e-waste sites were shown by Wu and co-authors (2008). Frazzoli and co-authors (2010) highlight the impacts of improper disposal of e-waste on the overall environment. It not only creates pollution, but also adversely affects the food chain, and thus health...