Study of Mercury-containing lamp waste management in Sub-Saharan Africa

13.1Risk assessment summary

During the disposal process, the intoxication risk from human exposure to mercury in the different stages of FL waste management is directly related to two main factors, namely the high number of FLs and the site characteristics where mercury is released (open or closed, the latter being an aggravating factor). Two main mechanisms have been identified with a potential risk to human health and the environment:

14Direct human exposure to high local concentrations of elemental mercury vapor released by a large number of broken lamps, which would be aggravated if release occurs in a closed space with poor ventilation, especially at the transshipment stage.

• 
  High local concentrations of mercury vapor may cause chronic or acute poisoning among people exposed to these emissions (mostly workers handling the EoL lamps) if the mercury concentration exceeds a certain limit (see 3.1.4). This risk is higher inside a building due to lower dispersion, and may therefore arise in the transshipment stages or at a recycling facility as described in the worst case scenario below, but most probably not for scavengers on a landfill who may gather many lamps in one place.
  

15Diffuse release of elemental mercury into the environment in all waste management stages.

• 
  The levels of diffuse emissions of elemental mercury during the processing chain are more difficult to predict but potentially more dangerous than high local concentrations. Elemental mercury can be transformed into methylmercury by microscopic organisms in soils and water, and bioaccumulate through the food chain. Elemental mercury released in airborne emissions during FL EoL waste management may remain in the atmosphere for up to one year. Wind can carry airborne mercury over great distances before it is deposited on land and in water bodies, primarily by rain and snow, contaminating remote places hundreds of miles away from mercury sources.⁴⁷ The route taken by the mercury from the point of emission depends on different factors, such as the form of mercury emitted, the surrounding landscape, the height above the ground of the emission point, and atmospheric factors (wind, rain, temperature…). However, the risk arising from these long-term/indirect airborne emissions is difficult to assess but can be compared with global mercury emissions. Influencing parameters have been identified: mercury is more readily transformed into methylmercury at high temperatures (Coupling mercury methylation rates to sulfate reduction rates in marine sediments, KING J. K., 1999) and under anaerobic conditions (Mercury Methylation in Macrophyte Roots of a Tropical Lake, Jane B. N. Mauro, 2004), which are common in landfills. The following diagram shows how elemental mercury from diffuse emissions is transferred to humans.
  

Figure (Source: Fraunhofer): Risk chain from elemental mercury emission to methylmercury ingestion

From the results of the worst-case scenario compared with very conservative standards (see the summary table below), we can infer that the main risks to human health are either low or can be mitigated.

Airborne pollution may only become significant in closed spaces, which would happen only in very specific situations such as:

9. 
   A combination of closed garbage trucks (large load capacity with press) and high concentration of FLs; or
   
10. 
    Breakage of a large number of FLs in a closed unventilated location (may lead to blood poisoning by inhalation of elemental mercury) – preventable with simple safety measures.
    

to the risk of water pollution leading to bioaccumulation of organic mercury throughout the food chain is low, but should not be neglected, although it is very complex to assess precisely.

Lamp breakage at home is not a significant threat and can be prevented by simple precautionary measures (ventilating the room and avoiding vacuuming of the mercury-containing powder).

Emission considered in the End-of-Life CFL treatment	Population exposed	Acceptable thresholds	Worst case scenario emission values	Estimated risk
Vapor mercury due to household lamp breakage	Household	1 mg/m^3 over several hours for AI	0.5 mg/m^3	Low
Vapor mercury due to lamp breakage during collection	Collection workers	0.1 mg/m^3 for CI 1 mg/m^3 over several hours for AI	0.04 mg/m^3 0.18 mg/m^3	Low Low
Vapor mercury due to lamp breakage during transshipment	Transshipment workers	0.1 mg/m^3 for CI	0.035 mg/m^3	Low
Vapor mercury due to breakage of an entire post-pallet during transshipment handling inside a building	Transshipment workers	1 mg/m^3 over several hours for AI	> 1 mg/m^3 at emission point < 1 mg/m^3 at 3 meters from emission point	Significant, but controlled with basic safety rules
Diffuse vapor mercury due to lamp breakage in landfill	Scavengers, neighboring households	0.1 mg/m^3 for CI	0.009 mg/m^3	Low
Peak vapor mercury due to lamp breakage in landfill	Scavengers	1 mg/m^3 over several hours for AI	> 1mg/m^3 at emission point over some seconds and disseminated by wind	Not significant
Soil and water pollution due to washed out mercury from the landfill and deposition of airborne mercury emissions	Neighboring population, consumers	0.5 µg/l in the water	0.3 µg/l	Low (but should be monitored)

Table : Summary of risk related to the worst case scenario

AI: Acute Intoxication; CI: Chronic Intoxication