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Worker Health Study Summaries

Research on long-term exposure

Methylene Chloride

NOTE: This page is archived for historical purposes and is no longer being maintained or updated.
NOTICE: These are NIOSH Archive Documents, and may not represent current NIOSH Policy. They are presented here as historical content, for research and review purposes only. This collection of Worker Notification Materials and any recommendations made herein are relevant for specific worker populations. The results do not predict risk for a given individual. The results may not be universally applicable.

1990

Study Background

An earlier study on men exposed to methylene chloride (MC) at an automobile body plant showed they had low sperm counts.  We wanted to see if furniture strippers who are exposed to MC also have low sperm counts.

We also wanted to measure how much MC furniture strippers typically are exposed to.

The study included 11 men exposed to MC.  They worked at five different furniturestripping companies

Methylene Chloride in Air

Exposure to MC was measured by workers wearing a pump. The exposures ranged from 15  parts per million (ppm) to 366 ppm.

366 ppm means 366 parts of MC for every million parts of air.   This is a measure of MC in air, but it does not measure MC absorbed through the skin.

The current OSHA legal standard is 500 ppm averaged over 8 hours.  Therefore, workers were exposed at levels below the OSHA limit.  However, OSHA is in the process of lowering the legal limit for MC.

Although this study was aimed at effects on sperm, NIOSH considers MC a potential human carcinogen (cancer-causing agent).  For that reason NIOSH recommends that exposures to MC be reduced to the lowest feasible limit. 

Sperm Concentration

The concentration of sperm in nsemen is measured as the number of sperm for every cubic centimeter (cc) of semen.  The average concentration of sperm in the 11 exposed workers was 54 million/cc.

The sperm concentration of  the exposed workers was within normal limits.  We found no consistent problems of semen or hormones with exposure to MC.

Carboxyhemoglobin (COH)

MC becomes carbon monoxide in the body.  Carbon monoxide becomes a substance in blood known as COHb.  This is measured as % of COHb.

COHb means the blood can’t carry as much oxygen as it should.   Since cigarette smoke contains carbon monoxide, smokers have higher COHb than non-smokers.

The COHb level for both smokers and non-smokers was a little above normal.  This may have been due to MC exposure.

Table of Results

Results Average Value For All 11 Exposed Workers Lowest and Highest ValuesFor All 11 Exposed Workers Normal Values
Methylene Chloride In Air 122 ppm 15 – 366 ppm See Above
Sperm Concentration
(million sperm per
cc of semen)
54 23 – 128  20 – 200
Carboxyhemoglobin - All 11 Exposed Workers 5.8 % 2.2 – 13.5 % Less than 2%
Carboxyhemoglobin - Non-smokers 3.9 % 2.2 – 5.9 % Less than 2%
Carboxyhemoglobin - Smokers 10.2% 8.1 – 13.5% 3 – 10%

Symptoms of Methylene Chloride Exposure

Workers are usually exposed to MC by breathing it or getting it on their skin.  Either way, MC can affect your health.

Symptoms of exposure include: headache, dizziness, nausea, giddiness, feeling irritable, and numbness or tingling in the arms or legs.  Repeated contact may cause a skin reaction.  It is irritating to the eyes and nose.

Very high exposure could cause a severe lung reaction, hallucinations, or even death.

Recommendations To Reduce Exposure to Methylene Chloride

Even though this study did not show that MC affects sperm, it is a good idea to avoid breathing MC or getting it on your skin.

  1. The best way to control MC in the air is local exhaust ventilation.   Also, the whole room where MC is used should have plenty of fresh air.
  2. Don't lean over a dip tank. A lot of MC is breathed in by doing this.   Use a pole to turn or retrieve objects in the tank.
  3. Use a removable metal basket to hold small parts in the tank.  A split lid on the dip tank may help prevent MC from getting into the air. A drying rack on the dip tank might help keep exposure down later during washing.
  4. Use an enclosed container to collect liquid that drains out.
  5. In order to use as little MC as possible and to avoid spills, try a slower flow rate on sprays.
  6. It may help to add chemicals known as vapor retarders to the MC.  These keep less MC from getting into the air.
  7. Put wet paint scrapings in an airtight container.
  8. Your company may be able to replace MC with a safer stripping chemical.
  9. Wash immediately after getting MC on your skin. Remove clothing soaked with MC immediately. Wear clean dry clothing every day.
  10. Wear special gloves, aprons, and shoe covers that MC can’t pass through.  Wear safety glasses, goggles, and faceshields as necessary.
  11. Respirators should only be used if the company has a respirator program in place. This is described in OSHAregulation 29 CFR 1910.134. Some types of respirators are not recommended for MC.
  12. Since MC and smoking both cause COHb to form in the blood, if you smoke, it would be a good idea to quit.  At least, don’t smoke in a room where MC is present.
 
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