E-waste contains a number of toxic substances, including plastics and heavy metals such as lead, cadmium, and mercury, which can cause serious adverse health effects.
Lead can be found in circuit boards and monitor cathode ray tubes (CRTs). Lead is particularly dangerous to the environment because of its ability to accumulate and persist in plants, animals, and microorganisms (Puckett et al. 2002: 11). The bioaccumulation of lead in the human body is particularly harmful because its primary target is the central nervous system. Lead can cause permanent damage to the brain and nervous system, causing retardation and behavioral changes. Infants and young children are particularly susceptible because of the impairment of cognitive and behavioral development it can cause (Ryan et al. 2004: 19A).
Cadmium can be found in SMD (surface mount device) chip resistors, infrared detectors and semiconductors (Puckett et al. 2002: 11). Like lead, cadmium is particularly toxic to humans because it accumulates in the human body and poses an environmental danger due to both acute and chronic toxicity (Puckett et al. 2002: 11). Renal damage is the most common effect of cadmium toxicity. Cadmium that enters the system through the gastrointestinal tract resides in human kidneys with a half-life of 10-20 years (Nordberg et al. 1985).
Mercury is the most prevalent toxic metal found in e-waste. It is in circuit boards, switches, medical equipment, lamps, mobile phones, and batteries. Mercury transforms into methylmercury in water, where it can accumulate in living organisms, typically via fish, concentrating in large fish and humans at the top of the food chain (Puckett et al. 2002: 11). Mercury is readily absorbed by the human body, ultimately inhibiting enzymatic activity and leading to cell damage (Boyer et al. 1959).
The most abundant component of e-waste is plastics. Plastics comprise almost twenty-three percent of a typical desktop computer (Microelectronics 1995). They are used for insulation, cables and housing for all electronic devices; the variety of products available for recovery complicates the de-manufacturing process. Due to the complex recovery process, large amounts of plastic e-waste are disposed of through landfills, incinerators and open burning, allowing toxic substances to leach into the environment.
Case Study: Guiyu, China
The town of Guiyu is located in the Chaozhou region of the greater Guangdong Province in southeast China. "Since 1995, Guiyu has been transformed from a poor, rural, rice-growing community to a booming e-waste processing center. While rice is still growing in the fields, virtually all of the available building space has given way to providing many hundreds of small and often specialized e-waste recycling shelters and yards" (Puckett et al. 2002: 17).
Along with this new e-waste recycling comes serious environmental and occupational health hazards. Hazardous recycling operations include toner sweeping, the open burning of dismantled computers, CRT cracking and dumping, circuit board recycling, acid stripping of chips, and plastic chipping and melting (Puckett et al. 2002: 20). The workers are at risk of inhaling the toxic fumes from the burning of the materials and ingesting contaminated water and food. They may also be exposed to toxins through dermal contact due to the lack of sufficient protective equipment.
Please see the Basel Action Network website to view a photo gallery of e-waste in Guiyu, China.
Large amounts of imported e-waste material and process residues never get recycled and are simply dumped in open fields; along riverbanks, ponds, and wetlands; in rivers; and in irrigation ditches (Puckett et al. 2002: 23-24). This indiscriminate dumping has exacerbated contamination of drinking water sources and sediments. Water samples from the Liangjiang River outside of Guiyu, China show cadmium and lead levels to be well above World Health Guidelines and EPA Drinking Water Standards (table 1).
Table 1. Guiyu Sample Results and Water Quality Comparison. Adapted
from Puckett et al., 2002.