Dichloromethane

Dichloromethane (DCM), also known as methylene chloride, is a widely used industrial solvent with applications in paint stripping, degreasing, and pharmaceutical manufacturing. 

While its volatility and effectiveness make it valuable in various industries, DCM exposure poses significant health risks, including neurological, respiratory, and carcinogenic effects, particularly in occupational settings.

What is Dichloromethane?

Dichloromethane (DCM), also known as methylene chloride, is a volatile, colorless liquid with a sweet, chloroform-like odor. It is widely used as an industrial solvent, paint stripper, degreaser, and in the manufacturing of pharmaceuticals, adhesives, and food products. 

It was used to decaffeinate coffee, but this has stopped chiefly due to concern about DCM persistence in the final product.

Despite its industrial utility, DCM poses significant health risks, primarily through inhalation and dermal exposure.

Dichloromethane Metabolism

DCM is metabolized via two pathways: a cytochrome P450-mediated oxidative pathway and a glutathione conjugation pathway. The oxidative pathway, catalyzed by CYP2E1, produces carbon monoxide as a byproduct, which can lead to elevated carboxyhemoglobin levels in the blood.

Key Properties

Key properties of dichloromethane include:

Chemical Formula: CH₂Cl₂

Molecular Weight: 84.93 g/mol

Boiling Point: 40°C (104°F)

Solubility: Slightly soluble in water, highly miscible with organic solvents

Routes of Exposure: Inhalation, dermal absorption, ingestion (rare)

Toxicological Effects of Dichloromethane

Toxicological effects of dichloromethane may vary depending on whether a person’s exposure is acute or chronic. 

Acute Exposure Effects

Short-term exposure to high levels of dichloromethane can cause immediate health effects, primarily affecting the nervous, respiratory, and cardiovascular systems. Symptoms may vary depending on the concentration and duration of exposure.

Neurological Effects

Acute DCM exposure can have the following neurological effects:

• Dizziness, headache, nausea, drowsiness, confusion
• Impaired coordination, memory deficits, and slowed reaction time
• Severe exposure can lead to unconsciousness, coma, or death due to central nervous system (CNS) depression

Respiratory and Cardiovascular Effects

Acute DCM exposure can have the following respiratory and cardiovascular effects:

• Coughing, throat irritation, and shortness of breath
• Increased carboxyhemoglobin levels (similar to carbon monoxide poisoning), leading to hypoxia and potential arrhythmias
• High concentrations can result in respiratory failure and cardiac arrest

Gastrointestinal Effects

Acute DCM exposure can have the following gastrointestinal effects:

• Nausea, vomiting, abdominal pain
• Inhalation of high concentrations may trigger reflexive vomiting and aspiration risk

Skin and Eye Irritation

Acute DCM exposure can have the following effects on skin and eyes: 

• Redness, irritation, and potential chemical burns from prolonged contact
• Eye exposure can lead to tearing, conjunctivitis, and corneal damage

Chronic Exposure Effects

Long-term exposure to lower levels of dichloromethane, particularly in occupational settings, is associated with serious systemic health risks, including organ toxicity and carcinogenicity.

Neurological Effects

Chronic DCM exposure can have the following neurological effects:

• Chronic cognitive impairment, memory loss, mood changes
• Fatigue, dizziness, and difficulty concentrating

Hepatic and Renal Toxicity

Chronic DCM exposure can have the following hepatic and renal effects:

• Liver damage, including fatty liver changes, hepatocellular vacuolation, and necrosis
• Kidney dysfunction with potential nephrotoxic effects

Carcinogenicity

Chronic DCM exposure has been linked to carcinogenicity:

• EPA & IARC Classification: "Probable human carcinogen" (Group B2)
• Increased incidence of liver and lung tumors in animal studies
• Possible associations with non-Hodgkin Lymphoma and multiple myeloma in occupational studies

Reproductive and Developmental Toxicity

• Limited evidence suggests potential risks for spontaneous abortion and fetal toxicity in workers with prolonged exposure
• Data on human reproductive harm remain inconclusive

Cardiovascular Effects

Chronic exposure to DCM can have the following cardiovascular effects:

• Chronic carboxyhemoglobin formation, reducing oxygen delivery to tissues
• Increased risk of cardiovascular stress and heart disease in long-term exposure

Regulatory and Safety Considerations

Given its toxicity, stringent safety measures are essential when handling dichloromethane:

Ventilation: Proper exhaust and air filtration systems

Personal Protective Equipment (PPE): Respirators, gloves, and protective eyewear

Exposure Limits:

• OSHA PEL: 25 ppm (8-hour TWA)
• ACGIH TLV: 50 ppm TWA (A2 – suspected human carcinogen)
• IDLH (Immediately Dangerous to Life or Health): 2,300 ppm

Who Should Get Tested for Dichloromethane Exposure?

The following groups of people may consider testing for dichloromethane:

Occupational Exposure 

Individuals working in industries that use dichloromethane are at the highest risk and should be monitored for exposure. These industries include:

• Paint stripping and refinishing.
• Various other manufacturing and processing industries, including rubber and plastics.

Symptomatic Individuals

Testing may be considered for patients presenting with symptoms linked to dichloromethane toxicity, especially if they may have recently been exposed to dichloromethane. 

Test Procedure and Interpretation

Testing for dichloromethane exposure involves measuring the chemical in exhaled air or blood, but these tests only detect recent exposure within a few days. Carboxyhemoglobin levels in blood and formic acid in urine can also be assessed, though they are not specific to dichloromethane. 

These tests are not routinely available in standard medical offices and are primarily used in occupational or environmental health assessments.

Interpreting High Dichloromethane Levels

Elevated levels of dichloromethane or its metabolites (e.g., carbon monoxide) indicate recent or significant exposure. The severity of symptoms often aligns with exposure levels.

Dichloromethane metabolism produces carbon monoxide, contributing to its toxicity. Blood carboxyhemoglobin (COHb) levels can serve as an indirect indicator of exposure.

Interpreting Low Dichloromethane Levels

Low or undetectable levels suggest minimal exposure to DCM or that significant exposure occurred some time ago.

Trace amounts may be present due to widespread industrial use, but this does not necessarily rule out long-term risks. Chronic health effects of low-level exposure remain under investigation.

A thorough occupational and environmental history is key to guiding further evaluation for patients with suspected exposure.

Order Toxin Testing

Click here to compare testing options and order testing to assess toxin levels.