Analytical Report Of Serial Poisoning Of Iranian Students (Part 4: Laboratory Findings for Diagnosis of Chemical Poisoning)

In the fourth instalment of this article series, we aim to present laboratory findings for diagnosing known gas poisonings. Additionally, we will delve into the long-term effects of chemical gas poisoning.

It is important to note that our primary objective at IIPHA is to investigate the possible factors contributing to the serial poisoning of Iranian students, using evidence and reports provided by them and the medical staff. As we do not have direct access to patients and laboratory samples, these articles are based solely on scientific sources available on the use of gases and known poisoning factors.

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Physicians utilize various tests to diagnose different types of poisonings. While we cannot definitively comment on these tests due to our lack of direct access to patients and laboratory samples, the following tests are generally recommended for respiratory exposure to unknown chemicals:

  • Complete blood cell count, blood sugar, creatinine, electrolytes, blood oxygen levels (arterial oxygen), and urine tests
  • As complementary tests, liver function tests and lactate levels can also be requested
  • Chest X-ray, if necessary as, determined by the physician
  • Electrocardiogram (ECG), if required, to assess heart function

It is crucial to emphesise that only trained individuals should perform diagnostic and therapeutic actions. In some instances of poisoning, doctors may identify the potential type of contamination through initial clinical examinations, and additional tests may not be required. Diagnostic tests should only be conducted based on the physician’s opinion, and additional tests will be requested based on the doctor’s diagnosis, taking into account the patient’s symptoms and/or clinical examinations.

Without direct access to patients and laboratory samples, it may not be feasible to investigate and refer patients for specific toxicology tests, such as blood, urine, or saliva tests. Decisions regarding these tests must be based on the potential exposure type and the available facilities in medical centres. This report solely describes the available tests for potential poisoning.

Below are laboratory findings based on the type of exposure

Nerve agents – organophosphate compounds

Nerve agents are a group of organic chemicals derived from phosphoric acids and chemically related to organophosphates. These compounds are extensively used worldwide as pesticides, but they pose significant risks to human health by inhibiting the acetylcholinesterase enzyme, which can result in poisoning.

Depending on the type, these gases have different odours, but a garlic-like smell is a common characteristic and their colour ranges from colourless to pale yellow.

Symptoms of inhalation: Some of the common symptoms of nerve agent poisoning include pupil constriction, dizziness, muscle cramps, increased salivation, sweating, nasal discharge and tearing, nausea, vomiting, diarrhea and abdominal pain, shortness of breath, and headache. In severe cases, nerve agents can cause seizures, muscle spasms, paralysis, unconsciousness, and even death.

Laboratory findings: While laboratory findings can be helpful in diagnosing nerve gas poisoning, the primary basis for diagnosis is clinical symptoms. The decrease in plasma cholinesterase and red blood cell activity can indicate poisoning. Decreased blood oxygen concentration (O2 saturation) is another way to detect poisoning with this gas. Other non-specific changes, such as increased white blood cells, condensation, hyperglycaemia, and decreased blood magnesium and potassium, may also be observed.

Arsine gas

Arsine gas, also known as hydrogen arsenide, is a colourless inorganic gas with high flammability. While the odour of some gases may resemble that of garlic or rotten fish, relying on the human sense of smell alone is insufficient for detecting and preventing exposure quickly. This is because the human sense of smell could be more effective in detecting some types of gases, and it may not provide a timely warning of potential exposure.

Symptoms of inhalation: Common symptoms after exposure include weakness, headache, dizziness, restlessness, thirst, shaking or increased body temperature, increased heart rate, nausea, vomiting, abdominal pain, and shortness of breath. In severe exposures, poisoning symptoms may occur 30 to 60 minutes after exposure, but they can also occur with a delay of 2 to 24 hours after exposure.

Laboratory findings: This gas can cause haemolysis, i.e., decomposition and destruction of red blood cells. Therefore, the following tests can help detect arsine gas poisoning: complete blood cell count, haptoglobin measurement, urine test (for haemoglobinuria), and electrolytes (which can show increased blood potassium due to haemolysis). In case of severe renal failure, measuring blood creatinine and urine protein levels is necessary for diagnosis. Additionally, measuring blood and urine arsenic levels can be helpful in diagnosis.


Cyanide compounds are commonly used in the chemical industry and as pesticides. A bitter almond-like smell can detect the presence of this gas.

Symptoms of inhalation exposure: Burning sensation in the eyes and throat, headache, dizziness, shortness of breath, nausea, and vomiting are common symptoms of cyanide gas poisoning. In severe cases, convulsions, cardiovascular collapse, and death may occur.

Laboratory findings: metabolic acidosis, characterized by decreased bicarbonate levels in extracellular fluids and increased blood acidity, is the first sign of cyanide poisoning. Blood oxygen levels are usually normal unless there is severe respiratory distress, such as a coma. Measuring blood lactate levels and determining the amount of cyanide in the blood or red blood cells (red blood cell or plasma cyanide concentration) can help in diagnosis. Methaemoglobin levels can also be helpful in determining the need for continued treatment with antidotes. An electrocardiogram (ECG) may also be beneficial in the diagnostic process.


Phosgene is a toxic organic gas that can be used as a chemical weapon, but it’s also used in the production of herbicides and insecticides. It is a colourless compound and has a smell similar to mouldy hay, grass or spoiled fruit.

Symptoms of inhalation exposure: Severe burning of the respiratory tract and eyes, coughing, burning of the throat, shortness of breath, nausea, and vomiting are symptoms of phosgene poisoning.

Laboratory findings: Measuring arterial oxygen levels and detecting respiratory acidosis are crucial in diagnosing phosgene poisoning. Both tests may appear normal in the early stages, but if pulmonary edema occurs, oxygen and respiratory acidosis levels will decrease. A chest x-ray can also be helpful in detecting pulmonary edema.


What potential long-term physical effects can result from gas poisoning in school students?

The potential long-term physical effects of gas poisoning on students are a major concern for parents and educators alike. Many wonder if those affected by recent poisonings may develop future diseases or complications related to the recent incidents. The likelihood of long-term physical effects depends on three main factors: the type of substance, the level of exposure (gas concentration in the environment, duration of each exposure, and frequency of exposure), and the underlying health conditions of the affected individual.

As there is currently no access to the injured individuals and no official report has been published, providing a definitive answer is impossible. However, in general, short-term exposures to known gases in open spaces, especially for those who do not require hospitalization or special medical care, and do not exhibit severe symptoms, are unlikely to cause long-term physical effects.

It should be noted that prolonged and repeated exposure to highly toxic gases can result in long-term physical effects. Therefore, an accurate answer to this question can only be determined with access to accurate and scientific reports. It is essential that all possible measures are taken to prevent gas exposure in schools and other public spaces to ensure the health and safety of students and individuals.

The information on this topic is subject to change as new evidence emerges, and the report will be updated accordingly.