The living environment of humans contains numerous physical factors (such as temperature, atmospheric pressure, electrical currents, ionizing radiation, noise, and mechanical forces) and chemical factors (such as strong acids, strong alkalis, chemical toxins, and toxic substances from plants and animals) that can pose threats to health. This discussion focuses on diseases caused by common environmental physical and chemical factors, with emphasis on acute conditions.
Physical Causative Factors
Major physical factors in the environment that contribute to diseases include:
High Temperature
Exposure to high temperatures can result in heat illness or burns.
Low Temperature
Prolonged exposure to low-temperature environments may lead to conditions such as frozen rigor or frostbite.
High Pressure
High-pressure environments, such as underwater operations, can cause decompression sickness when rapid ascent occurs. This condition arises from nitrogen dissolved in the blood and tissues being released as bubbles, causing embolism, circulatory disturbances, and tissue damage.
Low Pressure
Low-pressure environments, often found at high altitudes or in mountainous regions, can lead to acute hypoxia during short stays, culminating in acute high-altitude sickness.
Electrical Current
Accidental contact with different types and intensities of electrical currents can cause electrical shock injuries, resulting in damage to tissues and organs.
Other conditions include drowning caused by accidental immersion during floods, water-related activities, or water sports; motion sickness (vertigo syndrome) caused by jostling, shaking, or rotation, often related to vestibular nerve dysfunction; noise-induced hearing loss; and ultraviolet or infrared radiation, which can cause skin damage.
Chemical Causative Factors
Chemical factors causing diseases originate from both natural sources (such as heavy metals and toxic substances in plants and animals) and industrial pollution (such as waste water, waste gas, and waste residues produced during the manufacturing of pesticides, drugs, and organic solvents). Many inorganic and organic chemical substances exhibit toxic properties and are collectively referred to as "poisons." These poisons can enter the human body through the respiratory tract, digestive tract, or skin and mucous membranes, leading to poisoning.
Pesticides
Pesticides kill harmful plants and animals but can unintentionally cause poisoning and even death in humans. Examples include poisoning from organic phosphorus insecticides, carbamate insecticides, rodenticides, and herbicides.
Medications
Overdosing on medications such as anesthetics, analgesics, sedatives, hypnotics, and central nervous system stimulants often results in poisoning. Chronic misuse or abuse of sedatives, hypnotics, or narcotic analgesics can cause drug dependence. Abrupt discontinuation or dose reduction can lead to withdrawal syndrome, characterized by neuropsychiatric disturbances.
Alcohols
Acute ethanol poisoning may occur from a single instance or short-term heavy alcohol consumption. Accidental ingestion of methanol causes damage to the central nervous system and optic nerves, metabolic acidosis, and, in severe cases, death.
Other Factors
Accidental ingestion of cleaning agents or organic solvents can cause poisoning. Asphyxiating compounds such as carbon monoxide, cyanide, and hydrogen sulfide lead to hypoxic poisoning. Strong acids or alkalis result in contact-induced tissue damage. Long-term exposure to toxic chemicals released during industrial production, which contaminate air or water, can cause chronic poisoning. Examples include poisoning from substances like thallium, mercury, and arsenic. Acute poisoning can also occur from accidental leaks of toxic chemicals or exposure to military-grade toxins. Poisoning caused by bites or stings from toxic animals such as venomous bees and snakes, or ingestion of animal toxins like pufferfish toxin and fish bile, is common. Additionally, poisoning from toxic plants such as poisonous mushrooms, aconite, datura, and oleander can occur as well.
Progress in Research on the Prevention and Treatment
Human understanding of chemical poisoning emerged relatively early. As far back as 500 BCE, it was recognized that toxins not absorbed into the bloodstream do not cause systemic poisoning. Most knowledge about poisoning has been accumulated through reported poisoning cases, epidemiological studies, and animal experiments. Before the 1930s, due to a lack of toxicological knowledge, there were no specific treatments for poisoning, and only general cleansing or supportive therapies were used. Subsequently, effective antidote therapies were developed through research combining physiology and toxicology, such as the use of sodium nitrite-thiosulfate for cyanide poisoning. In the 1940s, British Anti-Lewisite (BAL) began to be used for arsenic poisoning. During the 1950s, calcium disodium edetate was employed in the treatment of lead poisoning, and the use of chelating agents for metal poisoning became widespread. Iodine-containing pralidoxime was introduced for the treatment of organophosphate insecticide (OPI) poisoning. By the 1960s, sodium dimercaptopropanesulfonate (DMPS) was employed for the treatment of poisoning caused by metals and their compounds, such as antimony, lead, mercury, and arsenic. Recent discoveries have established that the pathogenesis of poisoning is linked to receptors, free radicals, lipid peroxidation, and intracellular calcium homeostasis, opening new avenues for exploring detoxification therapies. Since the 1970s, significant advancements have been made in poisoning diagnosis and treatment, owing to the rise of toxicology and the development of emergency medicine. Toxicology has delved into the mechanisms of poisoning from the organ level to the molecular and even genetic levels. Pharmacology research into targeted antidotes, along with advancements in emergency medicine technologies such as blood purification and organ support, has greatly enhanced the diagnosis and treatment of poisoning while improving prognosis.
Research into diseases caused by physical factors began later than that on chemical poisoning. In recent years, due to industrial development and military needs, studies have increasingly focused on the impact of harmful physical factors in the environment on human health, as well as human adaptability and maladjustments to environmental conditions. Significant progress has been made in these areas. Additionally, the application of advanced resuscitation technologies in emergency medicine has substantially improved the treatment outcomes for patients with high-altitude illness, electrical injuries, drowning, and similar conditions, reducing both disability and mortality rates.
Diagnostic Principles
Diseases caused by physical and chemical factors are characterized by clearly identifiable causes and specific clinical manifestations.
Etiology
These diseases typically occur under certain environmental conditions, and in most cases, their causes can be clearly identified with corresponding diagnostic methods. For instance, medication overdose or chemical poisoning can often be evaluated by estimating the toxic dose, while the concentration of toxins in the air can also be measured. Environmental parameters such as temperature, altitude, and seawater depth are quantifiable. With advances in detection methods and improvements in sensitivity and specificity, the etiology of most diseases caused by physical and chemical factors can now be accurately diagnosed.
Targeted Sites of Damage
Many toxins have specific target organs or areas of action. For example, OPI poisoning inhibits cholinesterase (ChE) after absorption, carbon tetrachloride primarily affects the liver, and the primary target of chronic benzene poisoning is the bone marrow. Physical factors also have specific sites of action, such as noise primarily affecting the auditory nerve and accelerated motion primarily impacting the vestibular nerve.
Dose-Effect Relationship
The dose-effect relationship represents the fundamental principle for evaluating the impact of physical and chemical factors. The severity of exposure, such as the amount of a toxin or the duration spent in extreme temperature environments, correlates with the severity of the illness and can serve as an indicator for evaluating prognosis.
Epidemiological Analysis
Many diseases caused by physical and chemical factors exhibit the characteristic of affecting large numbers of individuals within a short period. Epidemiological investigations analyzing disease patterns within affected populations are instrumental in identifying environmental causative factors and devising preventive measures.
Although diseases caused by physical and chemical factors often result in damage or failure of one or more organs, their clinical presentations are often nonspecific. Diagnosis requires considering environmental factors alongside a detailed review of exposure history, clinical manifestations, and laboratory investigations. Differential diagnosis with other clinically similar conditions, followed by a comprehensive analysis and evaluation, is essential for accurate diagnosis and treatment.
Principles for the Prevention and Treatment
Rapid Removal from Harmful Environments and Hazardous Factors
This constitutes the primary measure for managing diseases caused by physical and chemical factors. In cases of acute poisoning, exiting the source of toxin exposure and removing toxins from the body or skin are critical. This includes procedures such as decontamination, gastric lavage, and the use of blood purification therapies for toxins absorbed into the bloodstream. For individuals affected by conditions such as heatstroke or electrical injuries, transferring them to a safe environment is essential before initiating emergency resuscitation measures. On a routine basis, public education and preventive efforts play a crucial role in mitigating risks.
Stabilization of Vital Signs
Diseases caused by physical and chemical factors frequently lead to altered consciousness, respiratory and circulatory disturbances, or even failure. Patients often display instability in vital signs. The primary purpose of emergency resuscitation is to stabilize vital signs and enhance monitoring, thereby creating a foundation for further medical interventions.
Etiological and Pathophysiological Treatment
Treatment targeting the cause and pathogenesis of the disease is pivotal. For acute OPI poisoning, antidotes such as pralidoxime are used to reactivate phosphoryl cholinesterase, while drugs such as atropine and penehyclidine hydrochloride alleviate muscarinic symptoms. Naloxone is administered to competitively bind opioid receptors in cases of opioid poisoning. Flumazenil, which competes with benzodiazepine receptors, is used to treat benzodiazepine overdose and poisoning. Fomepizole, a potent inhibitor of alcohol dehydrogenase, is the first-line treatment for methanol and ethylene glycol poisoning. For methemoglobinemia caused by nitrites, aniline, or nitrobenzene poisoning, methylene blue is employed as a redox agent. For cyanide poisoning, sequential treatment with sodium nitrite and sodium thiosulfate is applied. Dimercaprol and sodium dimercaptopropanesulfonate act by binding heavy metals with sulfhydryl groups, forming complexes that are excreted in urine, thereby treating poisoning due to heavy metals such as arsenic, mercury, lead, copper, and antimony. Oxygen therapy is used as a primary treatment for carbon monoxide poisoning.
For diseases caused by physical factors, treatments focus on addressing the underlying cause. Cooling methods are utilized in cases of hyperthermia due to heatstroke, while rewarming is applied in cases of freezing or frost-related injuries. Acute high-altitude illness, primarily caused by hypoxia, responds to oxygen therapy as the main treatment strategy. Decompression sickness, which results from overly rapid pressure changes when transitioning from a high-pressure environment to a low-pressure one, is treated using a hyperbaric oxygen chamber to re-pressurize the patient, followed by gradual decompression.
Symptomatic and Supportive Treatments
For many diseases caused by physical and chemical factors, no highly specific treatments exist. Treatments are often symptomatic in nature to alleviate patient suffering. In some cases, supportive care for affected organs is necessary, serving as a transition until the thorough elimination of toxins and the recovery of organ function.
In conclusion, human survival is constantly impacted by various harmful factors in the environment, which pose significant threats to health. Thus, it is vital to acquire knowledge related to diseases caused by physical and chemical factors and implement preventive measures against foreseeable hazards. For individuals already afflicted, prompt diagnosis and effective treatment are necessary to facilitate recovery and restoration of health.