Health Risks

Nickel, is a natural element that constitutes approximately 0.009% of the earth's crust. Nickel sulfides, silicates and oxides are commonly used in mining and natural resources [EPA paper, source 2]. The most common nickel sulfide mineral is pentlandite [(NiFe)9S8] accounts for the majority of nickel produced globally [source 4,5]. Domestic nickel production comes from the smelting of natural nickel ores, refining nickel matte, an impure metallic sulfide product from smelting of sulfides of metal ores, reclamation of nickel metal from nickel based or non-nickel based scrap metal, including salvaged machinery, sheet metal, aircraft and other vehicular parts and discarded consumer goods such as batteries.

Nickel compounds are used in construction, mining, smelting, electrical equipment manufacturing, and battery and fuel cell production, among numerous other materials. During construction, there is a high risk for nickel contamination. They can also make their way into the household through ceramics since they often form the bond between enamel and iron.

Nickel compounds are so toxic because they are highly resistant to corrosion and oxidation in air and aqueous environments; they are resistant to corrosion by organic acids and exposure to chlorine, fluorine, hydrogen chloride and molten salts.

Est. average daily dietary intake is 0.1-0.3 mg/day [AUS sources 7,8] Less than 0.2 mg/day of which is consumed via food and 5-25 ug/day from water [AUS source 4]. Dermal exposure is one of the most common routes of exposure and even low levels of exposure may cause nickel allergic dermatitis. [AUS sources 16-18]

Common Effects:^[1]

• Gastrointestinal distress like: nausea, vomiting, and diarrhea
• Dermatitis (eczema like effects: rash, itchiness)
• Neurological effects
• Nickel specific asthma

Extreme Cases:

• Coma
• Death

Case Study

Sampleton, New South Wales, Australia:In 2004 Sampleton, New South Wales, Australia observed a huge spike in nickel concentration in their drinking water. (See graph) Although scientists don't know the exact reasons for how nickel concentrations increased so dramatically, as shown in figure 1, they hypothesize that it could be the result of a natural reduction of flow rate during a period of drought and the subsequent introduction of mine water into the drinking water supply. Overall fluctuations of nickel concentrations over the three years were attributed to natural dilution and changes in demands of water.

The Australian Drinking Water Guidelines mandates a safety threshold of 0.02 mg Ni/L water, a value that is based on 70 kg (154 lbs) average body weight, 2 L water consumed daily and 1000 as the safety factor to account for uncertainty of extending animal study results to humans. The residents of Sampleton are assumed to have a similar diet to the rest of Australia's population so that the results of the study can be extended to the whole country. The study also assumed that the entire population of Sampleton was nickel-sensitive. This would lead to a lower Lowest Observed Adverse Effect Level (LOAEL) and set stricter limit for tolerable mean nickel concentrations. The result of the study showed that the mean nickel concentration, 0.03 mg/L with a 95% confidence interval of 0.02-0.04 mg/L, is only approximately 7% of the LOAEL. Thus the mean nickel concentration in drinking water in Sampleton appears to have no health risks.

Although no real risks were detected, the town implemented increased surveillance of nickel concentrations and made plans to use alternative sources to supplement drinking water supplies during droughts. This study shows the importance of continued vigilance in maintaining high water quality standards at all times, had the concentration of nickel increased past the LOAEL, health effects could have been more drastic. [2]

[2]Alam, Noore, Stephen J. Corbett, and Helen C. Ptolemy. "Environmental Health Risk Assessment of Nickel Contamination of Drinking Water in a County Town in NSW." NSW Public Health Bulletin (2008): n. pag. Web. .

Current Remediation Techniques

Cyclic electrowinning/precipitation (CEP) : use of electrical current to transform positively charged metal cations into a stable, solid state where they can be easily separated from water and removed.
Drawback: concentration of cations must be high (threshold of 100 ppm)

Chemical precipitation: use of hydroxides and sulfides to precipitate cations.
Advantages:

1. Well-established, many available chemicals and equipment
2. Convenient, self-operating and low-maintenance due to closed system nature

Disadvantages:

1. Formation of toxic sludge from precipitate, which is environmentally and economically costly to remove
2. Requires extra flocculation/coagulation due to precipitation
3. Each metal has a distinct pH for optimum precipitation
4. Corrosive chemicals increases safety concerns

Ion exchange: reversible chemical reaction where ions from water or wastewater solution are exchanged for similarly charged ions attached to a stationary solid particle that are usually inorganic zeolites or resins.

Reverse osmosis: effective molecular filter to remove dissolved solutes through a membrane
Advantages:

1. Reduces concentration of all ionic contaminants, not just the heavy metal in question
2. Can be scaled up easily

Disadvantages:

1. Expensive
2. Requires high pressure
3. Too sensitive to operating conditions

Phytoremediation: use of plants to remediate heavy metals in contaminated soil, sludge, water etc.

Microbial remediation: use of microorganisms to degrade hazardous contaminants