Health and Safety Hazards
One of the most immediate drawbacks of calcium chloride is its direct hazard to human and animal health. Due to its hygroscopic nature, the compound actively pulls moisture from anything it touches, leading to potential burns and irritation.
Ingestion Risks
If ingested, calcium chloride can cause severe chemical burns to the mouth, throat, and gastrointestinal tract. In large enough quantities, it can lead to more severe systemic effects. These include vomiting, seizures, reduced heart rate, and even death. The exothermic reaction that occurs when the solid form dissolves adds to the danger, as it can cause thermal burns in addition to the chemical irritation.
Inhalation and Skin Exposure
Inhaling calcium chloride dust or mist can cause irritation and burns to the respiratory tract, leading to coughing, soreness, and shortness of breath. Direct skin contact, especially with moist skin, can result in burns, severe dryness, or dermatitis. Contact with the eyes can cause severe irritation and corneal damage. The risk is particularly high in occupational settings where the chemical is handled regularly.
Environmental Detriments
Aquatic and Soil Contamination
The overuse of calcium chloride, particularly as a road de-icer, poses a significant threat to local ecosystems. When runoff enters streams, rivers, and wetlands, it can increase the chloride levels in the water. High salinity is toxic to many aquatic organisms, including fish, amphibians, and invertebrates, and can drastically alter the biodiversity of the water body. Residual calcium chloride in the soil can also lead to salinization, which negatively affects agricultural productivity and soil permeability.
Vegetation Damage
High salt concentrations from runoff can be fatal to vegetation. As chloride accumulates in the soil, it damages the root systems of trees and plants, preventing proper water uptake and leading to dehydration. While some studies show minimal impact under controlled application, excessive or improper use can result in visible damage like stunted growth, wilting, and yellowing foliage.
Negative Impact on Concrete and Structures
For construction and infrastructure, calcium chloride presents several well-documented problems, despite its use as an accelerator.
- Corrosion of Steel Reinforcement: The chloride ions from calcium chloride can destroy the protective passive layer on steel reinforcement in concrete, leading to corrosion. This is a major concern for reinforced and prestressed concrete, and its use is prohibited in these applications by many industry standards.
- Increased Shrinkage and Cracking: The addition of calcium chloride increases the drying shrinkage of concrete, which can lead to a higher potential for cracking. This is especially problematic in patching and repair materials.
- Discoloration and Efflorescence: Calcium chloride can cause the finished concrete to darken unevenly, creating a blotchy appearance. It can also contribute to efflorescence, where white, insoluble deposits form on the surface.
- Reduced Sulfate Resistance: Concrete containing calcium chloride has a decreased resistance to sulfate attacks, a chemical reaction that causes deterioration.
Comparison Table: Calcium Chloride vs. Alternatives
| Feature | Calcium Chloride (CaCl2) | Magnesium Chloride (MgCl2) | Sodium Chloride (Rock Salt) | Calcium Magnesium Acetate (CMA) |
|---|---|---|---|---|
| Corrosiveness | High, especially to steel | Lower than CaCl2/NaCl | High | Low/Non-Corrosive |
| Effect on Plants | Moderate/High salinity risk | Moderate salinity risk | High salinity risk | Low impact on vegetation |
| Temperature Range | Works effectively at very low temperatures | Works at low temperatures, slightly less effective than CaCl2 | Ineffective below -9°C (15°F) | Works down to -27°C (-17°F), but slower |
| Cost | Relatively inexpensive | Moderately priced | Least expensive | Most expensive |
| Environmental Impact | Chloride runoff, soil salinization | Chloride runoff, soil salinization | High chloride pollution | Biodegradable, low toxicity |
Corrosion of Metals
Beyond its effects on reinforced concrete, calcium chloride is highly corrosive to metals in general. This is a crucial drawback in dehumidification applications where the salt is used to absorb moisture from the air. Storing calcium chloride dehumidifiers in areas with sensitive metal equipment, such as gun safes or vehicle interiors, can lead to rust and serious damage. In marine settings, prolonged exposure to the chemical can also cause corrosion to resistant materials.
Agricultural Concerns
Though used as a fertilizer, excessive use of calcium chloride can lead to chloride toxicity in plants. While some chloride is essential, too much can accumulate in the soil and affect nutrient uptake and seed germination. Plants that are sensitive to chloride are particularly at risk. An oversupply of calcium can also interfere with the uptake of other crucial nutrients like magnesium and potassium, leading to an overall nutritional imbalance.
Conclusion
While calcium chloride is a powerful and economical chemical with many uses, a thorough understanding of its disadvantages is critical. The significant health hazards associated with ingestion, inhalation, and skin contact necessitate strict safety protocols, including wearing personal protective equipment. Environmentally, its potential to contaminate water supplies and damage ecosystems requires careful management of runoff and application rates. Furthermore, its corrosive nature and detrimental effects on concrete and metals make it unsuitable for many construction and industrial applications. Weighing these considerable cons against its benefits is essential for any informed decision regarding its use.
For more detailed safety information, consult official Safety Data Sheets from reputable sources.
