2. How could mercury released from a broken CFL affect health?
- 2.1 How can inhaling or swallowing mercury affect health?
- 2.2 Does the amount of mercury released by a broken CFL affect health?
2.1 How can inhaling or swallowing mercury affect health?
The SCHER opinion states:
3. Opinion 3.1 question A
Assess the possible health risks to consumers, from the mercury released from accidental breakage of CFLs. In doing so, the SCHER is asked to consider risks to certain vulnerable groups of the population such as children or pregnant women.
Toxicology of elemental Hg
Effects of Hg0 inhalation in humans have mainly been characterised after accidental short-term and high-concentration exposures, and after long-term occupational exposures. After inhalation of very high concentrations, orders of magnitude above currently valid occupational exposure limits (e.g., the German MAK-value is 84 μg/m3) symptoms of acute toxicity characterised by restlessness, inflammatory responses in the lung, gastroenteritis and renal damage have been reported. In addition, neurotoxic symptoms such as tremor and increased sensitivity to stimuli are also reported.
After long-term Hg0 inhalation exposures, effects on the central nervous system and kidney apparently are the most sensitive end-points of toxicity. These include effects on a wide variety of cognitive, sensory, personality and motor functions. In general, symptoms subside after removal from exposure. However, persistent effects (tremor, cognitive deficits) have been observed in occupationally exposed subjects 10-30 years after cessation of exposure.
Persons in rooms after breakage of a CFL may be exposed to mercury by inhalation and by oral intake. After inhalation, more than 80% of inhaled Hg0 vapour is absorbed by the lungs. Ingested Hg0 is poorly absorbed in the gastrointestinal tract (less than 0.01%). Skin absorption is insignificant in relation to human exposure to mercury vapour. The elimination of Hg0 after inhalation is slow (half-life of inhaled Hg0 is 60 days) with most being eliminated through urine (as mercury ions) and faeces (as Hg0). A small amount of absorbed Hg0 is also eliminated via exhalation and sweat (ATSDR 1992; Goldman and Shannon 2001; Halbach and Clarkson 1978; Houeto et al. 1994).
Studies on workers exposed to Hg vapour have reported a clear increase in symptoms of dysfunction of the central nervous system at exposure levels greater than 0.1 mg/m3. Some studies also reported subtle neurotoxicity at lower concentrations. Self-reported memory disturbances, sleep disorders, anger, fatigue, and/or hand tremors were increased in workers chronically exposed to an estimated air concentration of 0.025 mg/m3. In a recent assessment of all studies on the exposure-response relationship between inhaled Hg vapour and adverse health effects, IPCS concluded that several studies consistently demonstrate subtle effects on the central nervous system in long-term occupational exposures to mercury vapour at exposure levels of approximately 20 μg/m3 or higher (WHO/IPCS, 2002 Hg).
The kidney is, together with the central nervous system, a critical organ for exposure to mercury vapour. Elemental mercury can be oxidized to Hg2+. The kidney accumulates inorganic mercury to a larger extent than most other tissue. High-dose exposure to Hg2+ may cause (immune-complex mediated) glomerulonephritis with proteinuria and nephritic syndrome. Effects on the renal tubules, as demonstrated by increased excretion of low molecular proteins, have been shown at low-level exposure, and may constitute the earliest biological effect occurring after long-term exposure to air concentrations of 25-30 μg Hg0/m3.
A large number of serious and even fatal intoxications have been described after ingestion of inorganic mercury compounds, but data from humans do not allow identification of no-adverse exposure levels, especially in long-term exposure. From studies on experimental animals, a No-Observed-Adverse-Effect Level (NOAEL) of 0.23 mg/kg per day was identified (US ATSDR, 1999; WHO/IPCS, 2002)
Children exposed to Hg0 vapours may exhibit symptoms like breathing difficulty, swelling and erythema of the hands and feet, and pealing pink skin at the tips of the fingers and toes. These symptoms are collectively called acrodynia (Albers et al. 1982; ATSDR, 1992, 1999; CDC 1991; Clarkson 2002; Isselbacher et al. 1994; Satoh 2000).
Children and the foetus during various stages of their development are more vulnerable than adults. Fast cell proliferation and migration occur during the second and third trimester of gestation and continues to occur in the first 2-3 years of age. Neural development extends from the embryonic period through adolescence (Rice and Barone, 2000). Since mercury inhibits cell division and migration during development, the foetus and young children are particularly at risk when exposed.
2.2 Does the amount of mercury released by a broken CFL affect health?
The SCHER opinion states:
A fluorescent light bulb contains 5 mg of Hg. Assuming release of the total Hg- content of a lamp after breakage into an average room, Hg concentrations in the range of or above occupational exposure limits (100 μg/m3) can be derived. These concentrations are also well above regulatory limits for Hg in a general environment. Regarding environmental exposures, the US EPA has defined a reference concentration (RfC) of 300 ng/m3, and the US CDC derived a maximum residue limit (MRL) of 200 ng/m3. However, it needs to be recognized that these concentrations are applied to life-long inhalation exposures, are based on conservative extrapolations, and are considered protective for all groups of the population, including potentially sensitive subgroups. . The US EPA also has defined an acute RfC of 1.8 μg/m3 for Hg. The acute RfC is an estimate (with uncertainty spanning an order of magnitude) of an acute continuous inhalation exposure (time weighted average with a duration up to 24 hours) without appreciable risks of deleterious effects during a life time for the human population also including sensitive subgroups.
The simple assumption of a complete evaporation of the Hg content from a broken light bulb apparently results in a wide overestimation of air concentrations of Hg over time. Indeed, most of the released Hg may re-condense, due to the low volatility of Hg. Measured data suggest that a broken CFL may produce Hg concentrations of 8 to 20 μg Hg/m3 for a short time after the breakage. Air concentrations rapidly decline: concentrations ≤2 μg Hg/m3 have been measured in a house two days after an Hg spill from a CFL. An experimental study indicates even lower concentrations, between 0.8 and 0.1 μg/m3 Hg0, depending on CFL lamp type, in a room after CFL-breakage (Fig. 1
However, the measured indoor air concentrations may not be indicative of the total Hg intake after a CFL breakage, since most of the Hg released may condense on surfaces, where it can persist if inadequate ventilation is present or in the absence of specific cleanup procedures. Equilibrium between Hg in air and condensed Hg will be reached and then Hg will be slowly oxidized to Hg ions. As a consequence, in addition to inhalation exposure, oral exposure to both elemental Hg and Hg ions may occur in children, due to ingestion of dust and hand-to-mouth contact. There are no data available on the potential contribution of such an exposure to total Hg-intake.
Compared to adults, children have higher exposure via various routes and internal doses of Hg due to several reasons. Children breathe more air per kg of body weight than adults at rest and tend to be more physically active than adults. Therefore, mercury vapours, if present in indoor air, may be delivered to children at higher internal doses than to adults (Miller et al. 2002). The foetus is also exposed during gestation as certain mercury species (HgCH3+) cross the placenta. A comprehensive review on mercury exposure in children is available in Counter and Buchanan (2004).
Since no data on the potential contribution of oral exposure to total Hg-intake are available for children, the SCHER recommends assessing potential Hg exposures from broken CFL lamps in an experimental setting specifically considering child behaviour. SCHER also recommends providing to customers specific instructions for Hg removal after breakage of a CFL and info for protecting children.
Based on the room air concentrations determined after breaking a CFL, a health risk for adults is not expected, since the exposure is in the range of occupational exposure limits for only a very short time. The occupational exposure limits are intended to protect adults for a 40-year work life. Due to the very low exposures and their very short duration, even sensitive subgroups in the adult population should be protected.
Given the measured Hg air concentrations after CFL breakage, the rapid decrease of these concentrations and the above-stated considerations on the RfC of Hg, the SCHER is of the opinion that a human health risk for adults due to CFL breakage is unlikely. Regarding risk for children, possible exposures from oral intake of dust and hand-to-mouth contact cannot be evaluated due to lack of scientific data; therefore, no conclusions on potential risk are possible. The external peak exposure to Hg0 by inhalation in adults after a CFL breakage is not translated into a sharp peak exposure of the foetus. Transfer of Hg0 from the maternal circulation to the foetus is limited. Therefore, foetal exposure is expected to be negligible.