Chrome, also known as chromium, is a metallic element that can have serious negative impacts on the environment. From contaminating water and soil to harming aquatic life and human health, chrome deserves its reputation as an environmental hazard.

What is Chrome and Where Does it Come From?

Chrome, or chromium, is a naturally occurring element found in rocks, animals, plants, and soil. The pure metal chrome is silvery-white and very hard and brittle. However, it is rarely found in its pure form in nature. Chrome is typically combined with other elements to form compounds called chromium salts. These salts are used in a variety of industrial processes that ultimately release chrome into the environment.

Natural Sources of Chrome

In nature, chrome is found in trace amounts in air, water, and soil. Volcanic dust and gases release a small amount of chrome into the atmosphere. Chrome can also enter surface water through the weathering of chrome-containing rocks and soil.

Anthropogenic Sources of Chrome

While natural sources account for a portion of environmental chrome, human activities are the major contributor to chrome contamination. Some of the top sources of industrial chrome emissions include:

Electroplating: Chrome plating uses chromium salts to deposit a thin layer of chrome onto metal parts. This helps prevent corrosion and wear. Chrome emissions can occur during the plating process.
Chemical Manufacturing: Chrome is used to produce pigments, dyes, mortars, and other chemical products. Chrome pollution occurs during manufacturing.
Leather Tanning: Chrome salts help stabilize and harden leather. Chrome effluents result from the tanning process.
Textile Manufacturing: Chrome is used as a dye fixative on fabrics and fibers. This produces chromium-laden wastewater.
Steel Production: Chrome is added to steel to increase hardness and corrosion resistance. This process releases chrome particulate matter.

As you can see, many industrial applications rely on chrome compounds and end up releasing chrome into the environment through their waste streams. Improper disposal of equipment and waste from these industries is a major pathway for chrome pollution.

How Does Chrome Contaminate Water and Soil?

Once released into the environment from natural or industrial sources, chrome compounds can persist and accumulate in water and soil systems. This leads to contamination that can be harmful to ecosystems and human health.

Water Contamination

Chrome water pollution occurs when chromium-laden wastewater is released directly into surface water or seeps into the groundwater supply from soil contamination. This can create unsafe levels of chrome in drinking water sources.

Some ways chrome enters and contaminates water include:

Industrial Discharges: Manufacturing waste streams high in chromium dumped directly into lakes, rivers, or oceans.
Leaching from Landfills: Chrome from improperly disposed industrial waste and equipment leaching from landfills into groundwater.
Surface Runoff: Rainwater washes over chrome-contaminated soil and carries it into streams, rivers, and lakes.
Groundwater Leaching: Chrome seeps through the soil and enters aquifers that feed wells and springs.

Once in surface water or groundwater, chrome persists and accumulates over time to potentially dangerous concentrations.

Soil Contamination

Chrome pollution in soil can occur near mining operations, landfills, or industrial facilities that release chrome into the environment. Contaminated surface soil can also leach down into deeper soil layers.

Some common ways soil becomes contaminated with chrome include:

Mining Equipment: Improper disposal of chrome-containing mining waste, tools, and machinery.
Industrial Spills: Accidental spills of chrome solutions or waste at chemical plants.
Leaking Storage Tanks: Underground storage tanks at industrial sites can leak chrome compounds into surrounding soil.
Irrigation Water: Crops irrigated with chrome-contaminated water absorb and accumulate chrome in the soil.
Atmospheric Deposition: Chrome particulate matter from industrial processes settling onto soil.

Once in the soil, chrome does not break down and can persist near the surface or leach further down over time, leading to buildup in topsoil and subsoil.

How Does Chrome Harm Aquatic Life?

Once chrome enters waterways through contamination, it can be extremely toxic to aquatic plants and animals. Here are some of the major ways chrome harms aquatic life:

Bioaccumulation in Fish and Shellfish

Chrome builds up in the tissues of fish and shellfish exposed to contaminated water. Fish absorb chromium through their gills, which causes tissue damage.
Predatory fish accumulate increasing amounts of chrome as they consume smaller contaminated fish and organisms.
Fish eggs and larvae are especially sensitive to chrome, which can prevent successful breeding.

Toxic Effects in Aquatic Organisms

Chrome causes physiological and biochemical impairments in aquatic plants and animals. It inhibits growth, photosynthesis, and causes cell damage.
High chrome concentrations disrupt the endocrine systems of fish and other organisms, preventing reproduction.
Chrome exposure harms the gills, liver, kidneys, and stomach lining of fish and shellfish.

Increased Mortality Rates

Elevated chrome levels lead to higher mortality rates in juvenile fish and shellfish, preventing populations from thriving.
Older fish experience greater susceptibility to other stresses and diseases due to chrome weakening their immune systems.
Mass die-offs of fish and plant life can occur in water bodies with exceptionally high chromium levels.

Disruption of Aquatic Food Chains

Population declines in small aquatic organisms like plankton and shrimp disrupt the diets of larger fish who feed on them.
Reproductive issues reduce the abundance of fish available as prey for larger aquatic predators.
Bioaccumulation of chrome magnifies up the food chain, impacting each trophic level.

Chrome can enter aquatic ecosystems through various pathways and proceeds to inflict an array of detrimental effects. Implementing chrome pollution prevention measures is crucial for maintaining healthy waterways.

Health Impacts of Chrome Exposure on Humans

Chromium can be toxic to humans as well, whether it enters our bodies through contaminated food and water or airborne exposure. Especially concerning are health risks from long-term occupational chrome exposure.

Oxidation States and Toxicity

The health impacts of chrome depend greatly on its oxidation state:

Chromium(III): Chromium with a +3 charge is the most stable form in nature. It is an essential nutrient for metabolism and insulin function when consumed in trace amounts. However, excessive chromium(III) can still cause skin rashes, stomach ulcers, kidney and liver damage.
Chromium(VI): The +6 oxidation state is highly toxic and known to cause cancer. Chromium(VI) compounds easily enter cells and damage DNA. Industrial chromium is often converted into this carcinogenic, water-soluble form.

Health Effects of Chrome Overexposure

Even chromium(III), the less toxic form, can inflict organ damage and other problems when overexposure occurs:

Allergic Reactions: Skin contact with chromium can cause severe allergic reactions, rashes, and skin ulcers. Inhaled chrome dust has similar effects on the nasal mucosa and respiratory tract.
Kidney & Liver Damage: Excess chromium is filtered out through the kidneys and concentrated in the liver, leading to tissue damage with prolonged exposure.
Reproductive Issues: Chrome exposure has been linked to reproductive problems including sperm damage and miscarriages.
DNA Damage: Higher levels of chromium can cause mutations in DNA that disrupt normal cell function and potentially cause cancer.

Occupational Exposure Concerns

Workers in industries that use chrome compounds are at the greatest risk for overexposure. Health organizations have set occupational exposure limits for airborne chromium. However, high levels of exposure over months or years still occur, leading to:

Respiratory tract irritation and lung cancer from inhaling chrome dust and fumes
Dermatitis and skin ulceration from contact with chromium solutions
Higher risk of sinus, nasal, and lung cancer even at permissible exposure limits

Proper industrial hygiene practices and workplace air monitoring are essential to protect the health of workers exposed to chrome compounds daily.

Why is Chrome Considered Toxic and Carcinogenic?

The toxicity and carcinogenic properties of certain chromium compounds, especially chromium(VI), are well supported by scientific research. Here is an overview of these major health hazards posed by chrome:

Toxicity of Chromium Compounds

The toxicity of chromium depends on its valence state. Chromium(VI) compounds are over 100 times more toxic than chromium(III) forms.
Soluble chromium(VI) compounds, like sodium chromate, readily enter cells through sulfate channels and are therefore very toxic.
Once inside the cell, chromium(VI) gets reduced to chromium(III), producing free radicals and oxidative stress that damage proteins, membranes, and DNA.

Carcinogenic Effects

Chronic inhalation exposure to chromium(VI) compounds is classified as carcinogenic to humans by research and health organizations.
Occupational exposure to chromium(VI) has been clearly linked to an increased risk of lung cancer. Workers exposed to high levels have up to 50 times greater lung cancer mortality.
Nasal mucosa damage from inhaled chromium(VI) also leads to increased nasal and sinus cavity cancers.
The carcinogenic mechanisms likely involve DNA damage and mutations induced by chromium inside cells.

Other Adverse Effects

Studies show chromium(VI) compounds can damage sperm cells and the male reproductive system.
Contact dermatitis, skin ulcers, and allergic reactions are common with both chromium(VI) and chromium(III) overexposure.
Kidney and liver tissue damage occurs as these organs try to filter out excess chromium from the blood.

The human health hazards posed by certain chromium compounds are significant, especially from occupational exposures. Using alternative metals and compounds where possible can help mitigate these risks.

Conclusion

In summary, chrome has earned its reputation as an environmental pollutant and human health hazard due to a variety of factors:

Industrial processes are the major source of chromium contamination of air, water, and soil.
Chrome bioaccumulates in aquatic life and harms physiological functioning, reproduction, and survival.
Excessive chrome exposure through contaminated food and water can damage human organ systems.
Occupational inhalation of chrome dust and fumes poses significant cancer risks and other health effects.
The carcinogenicity and toxicity of certain chrome compounds like chromium(VI) are well supported.

Reducing the use and release of chrome in industrial processes is an important step to lessening its environmental footprint. Additionally, proper waste disposal and pollution prevention practices can help minimize chromium contamination. With increased awareness and advances in technology, hopefully alternatives to chrome can be adopted to achieve both industrial and environmental health.

References

Dong, D., & Li, X. (2019). Human Health Risk Assessment of Chromium in Soil Contaminated by Leather Tanning. International journal of environmental research and public health, 16(24), 4932. https://doi.org/10.3390/ijerph16244932
Kimbrough, D.E., Cohen, Y., Winer, A.M., Creelman, L. & Mabuni, C. (1999). A Critical Assessment of Chromium in the Environment. Critical Reviews in Environmental Science and Technology, 29(1), 1-46. https://doi.org/10.1080/10643389991259169
Costa, M. & Klein, C.B. (2006). Toxicity and Carcinogenicity of Chromium Compounds in Humans. Critical Reviews in Toxicology, 36(2), 155-163. https://doi.org/10.1080/10408440500534032
Jacobs, J.A. & Testa, S.M. (2005). Overview of Chromium(VI) in the Environment: Background and History. In Chromium(VI) Handbook. CRC Press. https://doi.org/10.1201/9781420039068.ch1
Cempel, M. & Nikel, G. (2006). Nickel: A Review of Its Sources and Environmental Toxicology. Polish Journal of Environmental Studies, 15(3), 375-382.
Environment Protection Agency (EPA). (1998). Toxicological Review of Trivalent Chromium. EPA/635/R-98/004F.
Gibb, H.J., Lees, P.S., Pinsky, P.F., & Rooney, B.C. (2000). Lung Cancer Among Workers in Chromium Chemical Production. American Journal of Industrial Medicine, 38(2), 115-126. https://doi.org/10.1002/1097-0274(200008)38:2%3C115::AID-AJIM3%3E3.0.CO;2-Q
Myers, C.R. (2012). The Effects of Chromium(VI) on Freshwater Fish. Environmental Pollution, 160(1), 159-164. https://doi.org/10.1016/j.envpol.2011.09.006
Barceloux, D.G. & Barceloux, D. (1999). Chromium. Journal of Toxicology: Clinical Toxicology, 37(2), 173-194. https://doi.org/10.1081/CLT-100102418