Information about MCHM
2014 West Virginia Chemical Release
4-methylcyclohexanemethanol (MCHM) is a chemical used to process coal. MCHM does not explode or catch fire. As a class of organic alcohols, it has an obvious odor and is reported to smell like licorice.
What is the acceptable level of MCHM in drinking water?
There should be no MCHM in drinking water. Following a chemical release, communities may need to determine when it would be appropriate to issue an alert about the potential risks of drinking water with low levels of MCHM present. Scientists have recommended a screening level of 1 ppm (parts per million) for drinking water. A level of 1ppm or below is not likely to be associated with any adverse health effects. Additionally, the public may continue to use tap water for cooking and consume food which may have been prepared using tap water, as with food cooked in restaurants with water at or below 1 ppm. Also, there is no known risk for bathing in water at or below 1 ppm.
Due to limited availability of data, and out of an abundance of caution, pregnant women may wish to consider an alternative drinking water source until the chemical is at non-detectable levels in the water distribution system. For mothers with babies, there is no research that suggests consuming water with these low levels of MCHM poses any health risk to their baby. However, if you have any concerns, please consult your doctor.
How was the 1 ppm level calculated?
Few studies on this specialized chemical exist and most have been conducted on animals. Scientists used the limited information available about this chemical to calculate how much MCHM a person could ingest without resulting in adverse health effects. These calculations use uncertainty factors to take into account the differences between animals and people and to consider possible effects on special populations. An additional factor was applied to account for the limited availability of data. Based on the application of these uncertainty factors and the available research studies, scientists recommend a screening level of 1 part per million (1 ppm), or lower, of MCHM in drinking water.
CDC used the following calculation to establish a short-term screening level of 1 part per million (ppm) for the MCHM spill in the Elk River:
- DW Advisory = Drinking Water Advisory
- NOEL = No Observed Effect Level in the experimental species (100 mg/kg/day)
- BW = Body weight of a child (10 kg)
- UF = Uncertainty factors that address differences between animals and humans (10X), address differences accounting for sensitive humans (10x), and account for weaknesses in the toxicological database (10X).
- Intake = The estimated intake from drinking water of a 10 kg child (1 liter/day).
|NOEL (mg/kg/d)||BW (kg)||UF (unitless)||Intake (L/day)||DW Advisory (mg/L or ppm)|
What studies were used in calculating the 1ppm recommendation?
We evaluated several studies from the manufacturer of MCHM to develop the recommended level of 1 ppm. These included the Pure MCHM 28-day oral study and the Crude MCHM LD-50 oral study.
We then extrapolated downwards to come up with the recommendation for a level that we believe would not be associated with any adverse health effects. This methodology is widely accepted and commonly used in environmental public health and risk assessment.
Pure MCHM 28-day Daily Oral Study Details – Rats received 0, 25, 100, and 400 mg/kg/day, 5 days a week, for 4 weeks. In this study, the administration of 400 mg/kg/day for 4 weeks was associated with erythropoietic, kidney, and liver effects, including increased liver weight, inflammation, and kidney tubular degeneration. The study determined that the No Observed Effect Level was 100 mg/kg/day.
Crude MCHM Acute Single Dose Oral Study Details – Male and female rats were dosed with 500, 1000, and 2000 mg/kg, followed by a 14-day observation period. The acute LD50 was calculated as 933 mg/kg for males and 707 mg/kg for females.