Silica which is one of the most abundant elements in the earth’s crust has numerous industrial applications. From glass and ceramics to foundries and construction industry, diatomaceous earth is used in a multitude of industries. Considering the widespread industrial use of silica, one can assume that millions of individuals working in different industries are exposed to silica and the risks and benefits associated with its exposure.
While in optimal quantities, silica is known to produce a number of positive health effects, such as improved bone mineral density, delayed age-related memory loss, and improved skin elasticity, it is also important to consider that continued exposure to high concentrations of silica can produce several side effects on both mental and physical health of the exposed individual.
In this article, we are particularly discussing the immune system-related effects of silica.
The Immunological Aspects of Silica — What Research Says?
Macrophages are an essential component of the immune system. They are physiological scavengers that rid the body from dead cells and debris. According to this silica review, in addition to this, they are also responsible for phagocytosis — a mechanism through which anything foreign to the body is engulfed and digested by macrophages. Considering these functions of macrophages, we can suggest that their role in critical in defending the human body from any kind of harm caused by a foreign organism or substance.
Silica is known to influence the function of macrophages in both humans and animals. In a study conducted on mice, it was found that silica is toxic for macrophages. The study included administration of injectable silica to mice. Within 3 days of the injection, it was found that silica blocked the innate immune response to sheep erythrocytes (a foreign substance) and caused complex alteration in the spleen cell responsiveness. Overall, silica produced an immune-depressive effect; however, the intensity of effect was different for different preparations of silica.
Another study published in the Journal of Immunotoxicology suggests that silica produces dysregulation of the immune system. The study emphasizes the fact that while silica can produce locally-restricted effects, there is no denying the fact that a possibility for systemic effects exists.
Silica and asbestos both are known to produce respiratory side effects. Inhalation of fine dust containing silica produces a condition called Silicosis, which is characterized by symptoms of cough, shortness of breath, fever, and cyanosis (bluish coloration of membranes due to lack of oxygen).
The study says that silica causes alterations in the function of alveolar macrophages and produces a chain of biological events that may influence the normal respiratory function. These respiratory symptoms can evolve into more serious, systemic immunological effects as well. The findings of the study conclude that silicosis and continued abnormal exposure to silica increases the incidence of autoimmune disorders (conditions in which the immune system considers the healthy cells as foreign bodies and targets them). Apart from autoimmune disorders, silicosis is likely to increase the risk of developing lung cancer as well. This leads us to the assumption that increased exposure to silica reduces the tumor-immunity of the host.
In addition to tumor, exposure to silica can also reduce an individual’s immunity against infectious diseases as well. Exposing experimental animals to silica makes them more susceptible to certain infections caused by different bacteria, viruses, and parasites. In these studies, silica was administered to animals through parenteral route and, therefore, the results may or may not be applicable to the oral preparations of silica.
What makes the finding more complex to comprehend the fact is that reduced phagocytic potential of macrophages is not the only mechanism responsible for reduced immunity. In fact, silica also influences the production of interferons and sensitivity of macrophages to prostaglandins as well, both of which play a major role in the defense mechanism.
A review published in Acta Biomedica suggested that the biological reactions produced inside the body when an individual is exposed to silica are only due to changes in innate immunity, but adaptive immunity as well. The review also suggests that ingestion or exposure to silica results in the death of key immunity cells, macrophages, which produce cytokines to stimulate fibroblasts. The end result of this entire mechanism is the formation of fibro-hyaline tissue and the classical symptoms of silicosis occur.
An interesting conclusion made by the review is that exposure to silica results in silicosis, which in turn is related to several other diseases, such as rheumatoid arthritis, lupus erythematosus, and scleroderma. It’s interesting because on one hand, research advocates the role of silica in joint disorders and age-related bone degeneration, but on the other hand, silica itself increases the risk of an individual of developing rheumatoid arthritis. While rheumatoid arthritis is an auto-immune disease, and osteoporosis and osteoarthritis are not, both of them influence bones and joints, and confusing rheumatoid arthritis for osteoarthritis can lead to serious complications arising from the use of silica as a possible drug for delaying age-related bone degeneration.
Concluding the Findings
After a thorough evaluation of the immunological effects of diatomaceous earth in both animals and humans, one can easily understand the fact that silica depresses the immunity and increases the risk of different health-related disorders, including tumors, respiratory diseases, autoimmune disorders, and infections.
It cannot be concluded whether all forms of silica produce the same effect or silica dust or intravenous silica are only responsible for immunodepression. In addition to this, consensus needs to be built regarding the doses at which silicon toxicity occurs. This is important because silica has shown several positive health effects when used in optimal doses and it can be a useful drug because of its non-toxic nature at low doses. Therefore, more scientific evidence is required in order to determine the risk-benefit ratio for this element that possesses for harmful and beneficial health effects.