Computer monitors and older TV picture tubes contain an average of four pounds of lead and require special handling at the end of their lives. In addition to lead, electronics can contain chromium, cadmium, mercury, beryllium, nickel, zinc, and brominated flame retardants. When electronics are not disposed of or recycled properly, these toxic materials can present problems.
Cadmium - found in chip resistors, infrared detectors, and semiconductors

Cadmium can accumulate in,and negatively impact, the kidneys. Cadmium is persistent, bio accumulative, and toxic. The principal exposure pathway is through respiration and through our food.
Lead - found in glass panels in computer monitors and in lead soldering of printed circuit boards

Lead can cause damage to the central and peripheral nervous systems, blood systems, and kidneys in humans. Lead has also been shown to have negative effects on the development of children's brains. Lead can accumulate in the environment and have a detrimental effect on plants, animals, and humans. Consumer electronics may be responsible for 40% of the lead found in landfills. The principal pathway of concern is lead leaching from landfills and contaminating drinking water supplies.
Mercury - found in thermostats, position sensors, relays and switches (e.g., on printed circuit boards), discharge lamps, and batteries. It is also used in medical equipment, data transmission, telecommunications, and mobile phones.

When mercury make sits way into waterways, it is transformed into mentholated mercury in the sediments. Mentholated mercury accumulates in living organisms and travels up the food chain. Mentholated mercury can cause brain damage. The principal exposure pathway is through our food.
Hexavalent Chromium or Chromium VI - can be used to protect against corrosion of untreated and galvanized steel plates

Chromium VI can damage DNA and has been linked to asthmatic bronchitis. The major pathways are through landfill leachate or from fly ash generated when materials containing Chromium VI are incinerated.
Brominated Flame Retardants - found on printed circuit boards, components such as plastic covers and cables as well as plastic covers of televisions

Although less is known about BFRs than some other contaminants of concern, but research has shown that one of these flame retardants, Polybrominated Diphenylethers (PDBE) might act and an endocrine disrupter. Flame retardant (Polybrominated Biphenyl's (PBB) may increase cancer risk to the of the digestive and lymph systems. Once released into the environment through landfill leachate and incineration they are concentrated in the food chain.
Plastic - Because manufacturers use many different types of plastic in electronic equipment, it is the most challenging to recycle. These plastics often include contaminants such as metal screws and inserts, coatings and paints, foams, and labels. Currently, plastics from electronic equipment are both difficult and costly to sort for single resin feedstocks markets and there are limited markets for the mixed plastics stream. Also, plastics can be treated with brominated flame retardants, making them harder to recycle and possibly dangerous to those exposed to them. Additionally, electronics are made with valuable resources such as precious metals, engineered plastics, glass, and other materials—all of which require energy to manufacture. When equipment is thrown away, these resources cannot be recovered and additional pollution will be generated to manufacture new products out of virgin materials.