Metals such as magnesium, iron, and zinc are required elements for the human body to function; however, even non-toxic metals can become toxic at high enough doses. Metal contamination in soil, groundwater, and surface water is regulated based on potential toxic effects on humans and other organisms.
Environmental Impacts & Human Toxicity of Metals
Metals can enter the soil, water bodies, or groundwater if released into the environment. Certain heavy metals such as arsenic, lead, mercury, chromium, and cadmium can negatively effect reproduction and cellular function in fish and other aquatic species. Mercury, for example, can bioaccumulate in larger fish species that humans eat, such as tuna and salmon. Metals can cause multiple organ damage, cancer, and cellular damage in humans. Toxicity depends on several factors including, the dose, route of exposure (inhalation, ingestion, absorption), and chemical makeup. Characteristics of the exposed individual, such as age, gender, genetics, and the individual’s overall health, can also influence the toxicity effects of metals.
How Do Metals Get into the Environment?
Metals can be naturally occurring or be part of pollutants generated by human activity, including the following:
- Agriculture via application of pesticides or herbicides
- Recycling facilities, salvage yards, and lumberyards
- Welding and chrome pigment production
- Shooting ranges
- Peeling household lead-based paint
- Historical or urban fill material that contains materials from which metals can leach
Lead was formerly used as an additive to gasoline as an anti-knocking agent but was phased out in the 1970s after lead was discovered to be harmful. If lead is present in subsurface contamination, this can be potentially helpful in dating the impacts.
Cleanup Criteria and Methods
The United States Environmental Protection Agency (US EPA) sets soil and water standards for concentrations of individual metal contaminants. The Safe Drinking Water Act allows states to set and enforce their own standards if they are at a minimum as stringent as the federal standard.
Remediation and cleanup of metal contamination typically will include the following methods:
- Soil excavation and off-site removal – this option is typically more costly upfront but can clean up a site in a generally timely manner.
- Monitored natural attenuation – pollutants will naturally degrade over time by microbial processes. The length of time required to naturally degrade to concentrations that meet the regulatory criteria depends on the subsurface conditions and type/age of the contaminant.
- Phytoremediation – the use of plants and soil microbes to reduce concentrations or toxic effects (not a widely used method).
Options to achieve closure of a release involving metals without meeting the cleanup criteria are available and vary by state. If residual contamination is left in place, certain land and water use restrictions may be placed on the property (institutional controls). Additionally, requirements to maintain engineering controls such as maintenance of a concrete slab or vapor barrier may be established to minimize human exposure.
How Can VERTEX Help?
VERTEX has a team of environmental professionals that have the expertise to opine on the cause, origin, and timing of releases, determine the extent of the impacts, the necessary response activities, and the appropriate remedial efforts and regulatory reporting necessary to correct the environmental condition. We also have the experience to identify any potentially responsible parties and to evaluate costs for reasonableness, and our on-staff professionals are equipped to evaluate potential risks for underwriting clients.