Hexachlorobutadiene
Hexachlorobutadiene is an industrial byproduct of making chlorinated solvents.
In lab animals it mainly harms the kidneys, and the one real-world study in people found early kidney stress that eased after they moved away from contaminated land. It turns up in well under 1 in 100 US water systems, usually at trace levels far below the World Health Organization's 0.6 ppb guideline.
World Health Organization guideline, our line
0.6 ppb
There is no legal limit for hexachlorobutadiene. It is rarely found in US public water, and the research behind any number is thin.
Hexachlorobutadiene: what is it, and where does it come from?
Hexachlorobutadiene is a man-made chlorinated liquid with a turpentine-like smell that does not occur in nature.
It forms mainly as an unwanted byproduct when chlorinated solvents such as PCE, TCE and carbon tetrachloride are made, and it has been used in rubber making and as a solvent, heat-transfer and hydraulic fluid. It reaches water through industrial discharges, waste sites and contaminated groundwater.
It is rare in tap water: EPA's last national look, monitoring from 1987 to 1999, found it in under 0.4 percent of public water systems, with a median detected value of 0.25 ppb. It has not been part of EPA's later national surveys, so there is no recent national tap-water data, and contamination today is a local issue near chemical plants and waste sites.
Hexachlorobutadiene: why does it matter?
In lab animals the kidney is clearly the main target: the body turns hexachlorobutadiene into a kidney-damaging compound, and high doses over two years caused kidney tumors in rats. Human evidence is very limited.
The clearest study followed UK residents whose homes sat on contaminated land; they showed early markers of kidney stress that improved after they moved out, and that exposure was through the air, not drinking water. Whether it causes cancer in people is unsettled: EPA calls it a possible human carcinogen, while IARC says the evidence cannot classify it.
Our line, the World Health Organization's 0.6 ppb, is built on kidney effects in rats. The research behind it is thin, so a reading over it may or may not be harmful.
In EPA's 1987 to 1999 monitoring, hexachlorobutadiene was detected in 0.35 percent (Round 1) and 0.18 percent (Round 2) of public water systems, and only 4 of 22,736 systems in one 20-state cross-section exceeded EPA's 0.9 ppb health reference level.
ATSDR found only two human studies; the clearest, of UK residents living on contaminated land, found early kidney-stress markers that improved after they moved out.
ATSDR (CDC), Toxicological Profile for Hexachlorobutadiene, 2021
Cancer classification is split: EPA calls hexachlorobutadiene a possible human carcinogen, IARC says it cannot be classified for humans, and the US National Toxicology Program has not evaluated it.
ATSDR (CDC), Toxicological Profile for Hexachlorobutadiene, 2021
Hexachlorobutadiene: what do we grade it against?
The table below lists each level that applies to Hexachlorobutadiene, what it is based on and who set it, and says which ones are enforceable.
| Contaminant | Health-based level | Source (health-based) |
|---|---|---|
| Hexachlorobutadiene (ppb) | 0.6 WHO guideline, kidney effects, our line | WHO 2017, as listed in ATSDR 2021 |
| Hexachlorobutadiene, cancer screen (ppb) | 0.9 EPA one-in-a-million lifetime cancer risk | US EPA regulatory determination, 2003 |
Health-based levels come from peer-reviewed research and government risk scientists working without cost constraints, while legal limits are enforceable compromises. Your report grades to the health column.
What helps against Hexachlorobutadiene?
The approaches below are the ones people use for Hexachlorobutadiene at home. Each entry says what it does and what it cannot do, and not every one helps.
Direct fixes
Activated carbon, the standard treatment for industrial solvents
Carbon filtration is the usual tool for chlorinated industrial chemicals in drinking water.
We found no filter test data specific to hexachlorobutadiene. Check that a filter's performance sheet names it before relying on it.
Common questions about Hexachlorobutadiene
How would hexachlorobutadiene get into my water?
From industry, not nature. It is a byproduct of making chlorinated solvents and reaches water through industrial discharges, waste sites and contaminated groundwater. Contamination is local, near chemical plants and waste sites.
Does it cause cancer?
Unsettled. High doses caused kidney tumors in rats in one two-year study. EPA calls it a possible human carcinogen; IARC says the evidence cannot classify it. No study has looked at long-term, low-level drinking in people.
Sources cited for Hexachlorobutadiene
Every number on this Hexachlorobutadiene page traces to one of the 3 sources below: 1 peer-reviewed, 2 government or regulatory.