Methylene Chloride Medical Surveillance

In 1910.1052 App B the primary route of entry for methylene chloride is inhalation. Appendix B to 1910.1052 explicitly states inhalation as the principal route, so workplace controls and monitoring should prioritize preventing breathing in vapors.

Medical surveillance should look for central nervous system depression, possible cardiac effects from elevated carboxyhemoglobin, liver toxicity, and irritation to eyes and airways. Appendix B to 1910.1052 describes nausea, vomiting, light-headedness, decreased coordination, unconsciousness, and at very high exposures death as acute effects, and also notes skin and eye irritation from liquid contact.

Cardiac history is emphasized because methylene chloride is metabolized to carbon monoxide, which increases carboxyhemoglobin and can reduce oxygen delivery to the heart, raising the risk of cardiac damage or heart attacks in susceptible people. Appendix B to 1910.1052 specifically directs a focus on cardiac history and risk factors during the annual medical and work history.

Yes — physicians should document smoking history because smokers already have elevated carboxyhemoglobin, which increases their risk when exposed to methylene chloride. Appendix B to 1910.1052 explains that smokers, anemic workers, and those with heart disease are at higher risk from the additional carboxyhemoglobin produced by methylene chloride metabolism.

No — a periodic post-shift carboxyhemoglobin test is recommended but not required. Appendix B to 1910.1052 states that such testing is recommended as an index of carbon monoxide in the blood but clarifies it is a recommendation, not a mandatory requirement.

Clinicians should focus on the nervous system, cardiovascular function, and pulmonary function, and evaluate the worker's ability to use a respirator if required. Appendix B to 1910.1052 recommends these examinations to detect pre-existing conditions that increase risk and to establish a baseline for future monitoring.

The history should ask specifically about headache, dizziness, fatigue, chest pain, shortness of breath, limb pain, and irritation of the skin and eyes. Appendix B to 1910.1052 lists these symptoms as important to identify possible methylene chloride effects and to detect unusually high exposures.

Methylene chloride is metabolized in part to carbon monoxide, which binds hemoglobin and raises carboxyhemoglobin levels; occupational exposures have produced carboxyhemoglobin as high as about 12% at measured exposures. Appendix B to 1910.1052 describes the P-450 oxidative pathway that converts methylene chloride to carbon monoxide and notes measured carboxyhemoglobin increases in exposed workers.

Workers with heart disease, those with risk factors for heart disease, smokers, and workers with anemia are especially susceptible because reduced oxygen-carrying capacity or cardiac problems worsen the effects of increased carboxyhemoglobin. Appendix B to 1910.1052 lists these groups as at higher risk for toxic effects from methylene chloride exposure.

Because hobbies like furniture refinishing, spray painting, or paint stripping can create additional methylene chloride exposures that contribute to overall risk and affect medical evaluation. Appendix B to 1910.1052 specifically recommends including such nonoccupational exposures on the history form.

Chronic exposure may cause liver toxicity and is associated with an increased risk of cancer; animal studies show clear carcinogenicity and epidemiologic data are suggestive for humans. Appendix B to 1910.1052 summarizes rodent carcinogenic findings and OSHA's conclusion that methylene chloride is a suspected human carcinogen.

The medical surveillance program is designed to regularly observe exposed workers and aid early detection and treatment, even though it cannot detect cancer at a preneoplastic stage. Appendix B to 1910.1052 explains surveillance aims to monitor workers' health and support early clinical intervention as detection and treatments evolve.

Physicians should evaluate whether respirator use is advisable because some respirators place extra strain on the cardiopulmonary system, and methylene chloride affects the heart and lungs. Appendix B to 1910.1052 recommends assessing the advisability of respirator use as part of the physical examination.

Observation of CNS depression signs—such as decreased coordination, dizziness, or impaired vigilance—along with a physical exam provides the best detection of early neurological effects from methylene chloride. Appendix B to 1910.1052 emphasizes watching for these symptoms because they can affect safe work performance.

The appendix recommends, but does not require, periodic post-shift carboxyhemoglobin testing as an index of carbon monoxide in the blood and routine clinical evaluation focusing on CNS, cardiac, and pulmonary systems. Appendix B to 1910.1052 explicitly states the carboxyhemoglobin test is a recommended surveillance measure.

Because liquid methylene chloride can cause skin irritation or burns and also is absorbed through the skin, contributing to total exposure; medical exams should check for skin irritation and document any dermal exposures. Appendix B to 1910.1052 notes dermal absorption and skin/eye irritation as important clinical findings.

A questionnaire should include demographic information, detailed occupational history (jobs and industries with likely methylene chloride use), nonwork exposures (hobbies), medical history covering respiratory, cardiovascular, liver, CNS and hematologic issues, smoking history, and current medications. Appendix B to 1910.1052 provides an example checklist covering these topics to satisfy comprehensive or interim history requirements.

Physicians should carefully evaluate and document cardiac history and symptoms before clearance for work with methylene chloride, since increased carboxyhemoglobin can worsen cardiac conditions; additional cardiac testing (e.g., EKG) may be indicated. Appendix B to 1910.1052 stresses special emphasis on cardiac history and related symptoms in the annual medical evaluation.

Employers must ensure pulmonary function testing is done before a worker begins to wear a negative-pressure respirator and at least annually thereafter. This requirement and its purpose are described in 1910.1052 App B, which emphasizes lung function assessment for workers who must use certain respirators.

Recommended pulmonary function measurements include forced vital capacity (FVC), forced expiratory volume in one second (FEV1), the FEV1/FVC ratio, and comparison of measured FVC and FEV1 to predicted values corrected for age, sex, race, and height. 1910.1052 App B states these tests should be used to assess lung function and calculate percent‑predicted values to determine whether lung function is adequate for respirator use.

Pulmonary function testing must be conducted by a physician or other licensed health care professional experienced in pulmonary function tests. 1910.1052 App B explicitly requires that these evaluations be performed by qualified medical personnel.

The MC medical exam should include a focused physical exam of multiple systems: skin and appendages (e.g., irritated or broken skin, jaundice), head (facial deformities, scars, hair), eyes (scleral icterus, pupillary response, fundoscopic exam), chest and heart (standard exams, JVD, peripheral pulses), abdomen (liver span), nervous system (complete neurologic exam), and relevant laboratory and studies. See the summary list in 1910.1052 App B for the full set of recommended elements.

End-of-shift COHb testing is recommended but not required; however, any periodic COHb level above 3% for non‑smokers or above 10% for smokers should prompt an investigation of the worker and workplace. 1910.1052 App B explains the recommendation and gives those investigation thresholds.

Recommended laboratory tests include hemoglobin and hematocrit and alanine aminotransferase (ALT, SGPT); post‑shift carboxyhemoglobin (COHb) is also recommended periodically. These tests are listed under the Laboratory section of 1910.1052 App B.

The standard recommends pulmonary function testing and electrocardiogram (ECG) as part of the studies to evaluate workers exposed to MC. These are listed in the Studies section of 1910.1052 App B.

When an exam reveals unexplained symptoms or signs, the physician or licensed health care professional must order follow‑up testing and, when appropriate, refer the worker to a specialist for further evaluation and treatment. 1910.1052 App B directs that further tests and specialist referrals be used to determine the nature and cause of the medical problem.

Employers must give the examining physician or other licensed health care professional a copy of the MC standard and relevant appendices, a description of the employee's duties and estimated exposure duration, a description of personal protective equipment used (including respirators), and any previous medical determinations related to MC that are within the employer's control. These employer obligations are listed in 1910.1052 App B.

The written opinion must state whether the employee has any medical condition that increases risk from MC exposure or from using respirators, recommend any restrictions on exposure or use of protective equipment, and state suitability to wear the assigned respirator; the physician must also inform the employee about MC's cancer risk and heart‑disease risk from CO metabolism. The written opinion must not contain specific findings or diagnoses unrelated to occupational exposures. See the Physicians' Obligations section in 1910.1052 App B.

The presence of facial hair or scars that might interfere with respirator fit should be noted during the exam and included in the written medical opinion regarding respirator suitability. 1910.1052 App B requires the physician to document such factors so employers can assess respirator assignment.

Yes; evaluation of oxygen‑carrying capacity (for example, measured red blood cell volume) is considered useful, particularly for workers with acute exposures to MC. 1910.1052 App B identifies this assessment as valuable because MC is metabolized to carbon monoxide, which reduces hemoglobin oxygen‑carrying capacity.

The physician should perform follow‑up procedures focused on the eyes, lungs, and neurological system; severe acute exposures may require hospitalization and the frequency of follow‑up exams should be determined by the treating clinician. 1910.1052 App B provides this guidance for managing acute exposures and significant symptoms.

Yes; the rule permits the physician or licensed health care professional to order additional tests and investigations as necessary to diagnose disease or clarify findings, and the employer is required to cover those additional medically necessary investigations. 1910.1052 App B states physicians may add appropriate tests as they become available.

The physician should inform the employee about the cancer risk associated with methylene chloride and about risk factors for heart disease and the potential for MC exposure to worsen underlying heart disease due to its metabolism to carbon monoxide. 1910.1052 App B requires that such information be communicated to the employee as part of the medical exam process.