More Than a Liquid: Understanding the Hidden Dangers of Solvents

In modern industry, a wide variety of solvents are frequently used in large quantities and for multiple purposes. However, to date, no ideal industrial solvent has been discovered that is non-flammable, non-explosive, non-toxic, and harmless to the skin. Solvents that pose no risk of fire or explosion often have toxic effects on the body; those that are non-toxic to the body are highly flammable, and most organic solvents carry risks of fire and explosion, as well as varying degrees of toxicity. Therefore, solvents should be regarded as toxic and harmful substances, similar to general chemical reagents. In particular, volatile solvents pose significant risks due to the toxicity, flammability, and explosiveness of their vapors. Even solvents with minimal volatility can be harmful when directly contacted.

The hazards of organic solvents generally refer to the relationship between solvents and humans. In other words, to gain a comprehensive understanding of the hazards of solvents, it is necessary to carefully consider three aspects: the inherent properties of the solvent, individual differences, and the relationship between humans and solvents.

1. Properties of Solvents

The physical and chemical properties of solvents are closely related to their hazards. For example, the melting point, boiling point, vapor pressure, vapor density, and evaporation rate of a solvent all determine how easily it can penetrate the human body. The solvent's solubility in water and fat, or its partition coefficient, determines how easily it can be absorbed through respiration, the digestive tract, or the skin. In summary, the ease with which a solvent is absorbed by the human body is an important reference factor in assessing the hazard of the solvent.

2. Individual Variations in Sensitivity to Solvents

The reactions that occur when organic solvents enter the body vary from person to person, as each individual has a different level of sensitivity to toxins. Some people may exhibit allergic reactions to certain solvents, while these same solvents have no effect on the majority of the population. These differences manifest in three aspects: the absorption of solvents into the body, their distribution and metabolism within the body, and the extent to which they are excreted from the body.

The amount and rate at which organic solvents enter the bloodstream from lung cells vary depending on respiration, blood circulation volume, blood composition, and the properties of lung cell membranes. The metabolism of solvents within the body, as well as the distribution and activity of enzymes related to metabolism, also vary significantly among individuals due to differences in physical constitution. Distribution and excretion exhibit even greater variability. Therefore, factors such as age, gender, nutritional status, physical constitution, medical history, genetics, and habits are important considerations in assessing an individual's sensitivity to solvent toxicity. The toxicity of a solvent is determined based on its effects on the majority of people. The dose of a toxin that can cause death when it enters the body is referred to as the lethal dose.

3. The relationship between humans and solvents

Solvents can be absorbed by the human body through the skin, digestive tract, or respiratory tract, causing toxicity. The common toxicity of most organic solvents to the human body manifests as an anesthetic effect when exposed to high concentrations of vapor. Inhalation of vapors can lead to drowsiness, unconsciousness, decreased blood pressure, and body temperature, ultimately resulting in death. In cases of mild poisoning, symptoms may include mental excitement, headaches, dizziness, nausea, palpitations, and difficulty breathing. These symptoms may arise due to disruptions in the central nervous system and hormonal regulatory systems caused by the solvent; the exact mechanisms remain under investigation. For example, the effect of ethanol on the central nervous system is generally believed to occur when ethanol enters the body and first acts on the cerebral cortex, causing excitement. As the effect of ethanol intensifies, the subcortical centers and cerebellum are affected, leading to impaired gait, ataxia, and other motor disorders. Finally, due to the inhibition of the medullary vasomotor and respiratory centers, collapse, respiratory distress, and death may occur. Some also suggest that ethanol promotes sleep due to the abnormal activation of the nervous system responsible for sleep physiology caused by acetaldehyde, a byproduct of ethanol metabolism in the body.

Solvents, in addition to causing paralysis, can also cause changes in the skin, cornea, and conjunctiva, with highly degreasing solvents requiring particular caution.