This is the English edition. The article body below is the publisher's English rendering of the original Chinese article; figures, license numbers and institutional names follow the original.

In one sentence: when e-waste is handled improperly, heavy metals such as lead, mercury and cadmium, together with dioxins formed by the incomplete combustion of chlorinated plastics, are released into soil, water and air and return to the human body through crops, drinking water and the food chain. Even prolonged storage alone causes the same migration, through rainwater leaching and the ageing of casings.

1. The Hazardous Ingredients in an Old Device

Electronic products achieve their function through materials, and their hazards reside in those same materials. Open up a scrapped device and you will find metal, plastic, glass and chemicals side by side, each behaving very differently in the environment.

  • Lead — found mainly in the funnel glass of older cathode-ray tubes and in solder; once in soil it degrades with difficulty and affects the nervous system and blood formation.
  • Mercury — volatile even at room temperature; mercury-containing lamps in LCD backlight modules and some relays are common sources.
  • Cadmium — common in nickel-cadmium batteries, contacts and older plastic stabilisers; highly mobile and readily taken up by crops.
  • Brominated flame retardants — used in circuit boards and casing plastics, they form brominated dioxins when burned.
  • Refrigerants and blowing agents — trapped in the insulation of refrigerators and air conditioners, they take part in atmospheric chemistry once released.

2. Heavy Metals Do Not Travel in One Step

Heavy metals do not move on their own; water, air and human activity carry them. The first pathway is rainwater leaching: waste casings left in the open are washed by rain, and soluble metal salts enter the soil profile with the leachate and then shallow groundwater. The second is surface runoff: drainage ditches around a dump site carry contaminants into rivers and canals, where they settle in sediment and become a long-term secondary release source.

The third pathway is bioaccumulation. Cadmium in soil is taken up by rice and vegetables and passed up the food chain, with concentrations magnified at higher trophic levels. The fourth is aerosol: fine particles from shredding and burning carry metals, spread with the wind and settle on nearby farmland and water surfaces.

3. Dioxin Formation Requires Three Conditions

Dioxins are not an ingredient of electronic products; they are formed during combustion. Three conditions must coincide: chlorinated organic matter, catalysis by metals such as copper and iron, and incomplete combustion. The polyvinyl chloride in cable insulation and casing plastics supplies exactly the chlorine source needed.

The “burn cables for copper” practice common in small workshops satisfies all three: open burning gives unstable temperature and insufficient oxygen, and the copper wire is itself the catalyst. Flue gas can also re-form dioxins in the cooling section, so even a high primary combustion temperature does not guarantee a dioxin-free exhaust. These compounds are strongly lipophilic; once deposited on pasture and ponds they enter livestock and fish, and eventually return to the dinner table.

This is where the inventory matters: once waste circuit boards are classified under HW49 in the National Hazardous Waste Inventory (2025 edition), their collection, storage and utilisation may only be entrusted to holders of a hazardous waste operating license.

4. Three High-Risk Non-Compliant Scenarios

One scenario is prolonged storage and crude landfill. Casings age and crack, dust and liquids inside come into direct contact with soil, and with no impermeable liner at the base of the pile, leachate migrates downwards. Another is acid leaching to extract precious metals. Strong acids or cyanide dissolve the metals and the spent liquor is discharged into soak pits or ditches, leaving soil acidity and metal concentrations above limits for years.

The third is open burning and rough shredding. Burning emits dioxins and metal-bearing fly ash, while shredding generates dust containing lead and brominated flame retardants, exposing both operators and nearby residents. What the three have in common is that pollutants enter environmental media without any collection or treatment.

These practices have their legal counterparts. Article 80 of the Solid Waste Pollution Prevention and Control Law requires anyone engaged in collection, storage, utilisation or disposal activities to hold a license, and illegal disposal of 3 tonnes or more also crosses the threshold for criminal liability.

5. Stored in Place, the Risk Does Not Stop

Many organisations lock old equipment in a storeroom and assume that with no dismantling and no burning there is no risk. That is not the case. Lithium batteries stored long-term carry risks of self-discharge and thermal runaway; mercury-containing lamps break under pressure; refrigerant in cooling equipment leaks slowly; and if the storeroom catches fire, the combustion products of plastics and cables are more complex than those of an ordinary fire.

From a management perspective, prolonged storage also brings three related problems: the ledger no longer matches actual stock and assets cannot be written off; there is no proof of compliant destination during fire-safety or environmental inspections; and as models become obsolete, recoverable components lose value until only the material price remains.

Nor can a storeroom be set up by simply marking out a patch of ground. The Standard for Pollution Control on Hazardous Waste Storage, GB 18597-2023, sets requirements for zoning, impermeable surfaces and ledgers, while the Measures for the Administration of Pollution Prevention and Control of Electronic Waste go down to the collection of dismantling wastewater and residues. The scope of work still depends on the license: certificate No. 1310250101 approves collection, storage and utilisation in separate segments.

6. Practical Notes

  • Register category, quantity and the location of hazardous components as soon as equipment enters the store; zone batteries and mercury lamps separately.
  • Make the storeroom impermeable, rainproof and leak-proof, with secondary containment under liquid-bearing components.
  • Do not burn cables or shred leaded glass yourself, and do not hand material to unqualified individuals to “take away and deal with.”
  • When delivering for treatment, obtain a statement of where the outputs go and handover documents confirming that waste circuit boards reach a licensed operator.
  • For stock held more than six months without treatment, reassess the fire-safety conditions of the storeroom and the data security risk.