Hexane is derived from petroleum.

It is a colorless, volatile liquid with a mild, gasoline-like odor.

It's in food.

Hexane is a human neurotoxic and narcotic agent.

It can simultaneously affect multiple nerves throughout the entire body (polyneuropathy).

Nerve biopsies in affected individuals show swelling of the nerve and thinning of the myelin sheath.

This has been observed at chronic exposure as low as 400 ppm in air.

Motor weakness and difficulties with vision may commence at much lower exposures.

Other effects associated with hexane toxicity include

  • Irritability

  • Confusion

  • Fatigue

  • Listlessness

  • Irritation to skin, eyes, lungs

  • Hair loss

  • Impotence

  • Reproductive system damage

  • Birth defects

  • Heart damage

  • Brain damage

Inhalation exposure limits are currently

OSHA PEL 500 ppm up to 8 hours (time weighted average, TWA)
NIOSH REL 50 ppm up to 10-hour work day and 40-hour work week
NIOSH IDLH 1100 ppm immediately dangerous to life or health

Ingestion limits are currently

EPA RfD 0.06 mg/kg per day (provisional RfD)
FDA none specified

Additional baseline information can be found here, here, here, and here.

High-protein meal is produced chiefly from corn and soybean processes that utilize hexane.

The meal is fed to beef and dairy cattle, hogs, poultry and other livestock.

According to an EPA report the average concentration of hexane in soybean meal after various stages of production is

0.152 gal/ton after ‘desolventizing toaster’
0.119 gal/ton after ‘dryer’
0.097 gal/ton after ‘cooler’

Following that first stage is when it is most cost-effective to convert processed meal into pellets for livestock consumption.

To express that concentration in ppm requires a little math. The conversion factors include

3.785 L/gal converts gallons to liters
0.660 kg/L specific gravity of hexane
0.454 lb/kg converts kilograms to pounds
ton/2000 lb converts pounds to tons


Hexane in meal pellets

That's ~ 70% above the NIOSH value for workday inhalation.

However, pellets are transported and stored in closed containers from the time of processing until placed into watertight plastic bags for transportation to feeding sites.

There isn't time or place for hexane to evaporate out of the food meal — meaning the livestock eat it.

So how does 86 ppm compare to the EPA provisional RfD of 0.06 mg/kg per day? Start with

Hexane equivalent

Next, the typical beef cow lives just 2 years before slaughter.

Using statistics at this cattle info site it is possible to model how much hexane a beef cow eats daily and during its lifetime.

For simplicity, midrange weights are used and the cow's growth is assumed to be linear between development stages.
This spreadsheet lets you have exactly the same model (HexaneCow zipped Excel 12 KB) .

Note — to be conservative, an assumption is made that the cow only absorbs and metabolizes 30% of the hexane ingested.

This may be an underestimate.

Hexane strongly bonds to protein during the extraction process.

It is difficult to remove and requires heat and/or other chemical processes to fracture the bond.

Stomach acid (HCl) achieves that separation, allowing hexane to be absorbed through digestive linings.

If you download the spreadsheet you can fiddle with the parameters to see how results are affected.

Also, the RfD for cows may not be the same as for humans, but the human value will serve as a good approximation for this model.

Here are key results (rounded)

1st month calf getting exposure 60x above RfD
24th month cow getting exposure 25x above RfD
cow has ingested 490 g hexane
cow has absorbed 150 g hexane
cow has a level of 250 mg hexane per kg body weight

If an 80 kg (175 lb) person consumes 0.55 kg (0.25 lb, a "quarter pounder") of this cow's beef, the exposure will be

Hexane beef consumption

which compares to the RfD as

Hexane beef exceeds adult limit

Similarly a 25 kg (55 lb) child who eats that same amount will be exposed to 90x the RfD.

Hexane is the dominate extraction solvent for oil seeds throughout the world, including soybean and other high volume oils used for human and animal consumption.

95% of the world's corn oil is produced from corn germ obtained by wet-milling.

The corn germ is dried, then shipped to hexane extraction facilities to obtain the oil.

A "hexane-free" corn oil with a 0.05% concentration of residual hexane remains a risk:

Hexane in oil

The amount of hexane ingested with 2 tablespoons of this oil is

14.787 ml/tbsp convert tablespoons to milliliters
0.924 kg/L specific gravity of corn oil

Hexane ingested in oil

For an 80 kg person, this compares to the RfD as

Hexane oil exceeds adult limit

Similarly a 25 kg (55 lb) child who eats that same amount will be exposed to 9x the RfD.

What about synergistic toxicity with other toxic residues?

For instance the herbicide atrazine (here, here, and here) is still used heavily in corn production.

This research highlights how atrazine

  • Disrupts hormones

  • Induces breast and prostate cancer

  • Correlates with other reproductive cancers

Currently there are no studies on how hexane and atrazine interact within the body.

How many head of cattle does it take before a cattle ranch's hexane output could be considered reportable under California's Toxic Release Inventory rules?

A cattle feedlot would have to handle at least 10,000 pounds of hexane and discharge at least 500 pounds. Let's check.

In the cow model above, it is assumed that 30% of the hexane is absorbed and retained by the cow.

That means the other 70% comes out of the cow one way or another.

In the second year, the cow consumes 290 g hexane, and the 70% excreted amounts to 200 g hexane.

Hexane report cattle

In other words, 5500 cows discharge enough hexane (500 lb) to require a report.

However, using the same math equation and substituting 10,000 lb hex (the handling requirement) and 290 g hex (the amount consumed per cow) equates to 76,000 cows.

According to this report, in March 2007 there were approximately 11.7 million head of cattle in feedlots, and larger feedlots accommodate between 50,000 and 100,000 head.

So somewhere there are feedlots that would qualify as major hexane polluters under the conservative cow model used above.

By the way, 11.7 million cows would be discharging an annual total of 1,000,000 lb hexane, or 500 tons.

That is a lot of hexane whether reported or not.

Seems like it should be counted among the other toxic gases, vapors and particles emitted from Concentrated Animal Feeding Operations (CAFOs).

There is remarkable overlap among among the symptoms of Bovine Spongiform Encephalopathy (BSE, "mad cow disease"), Transmissible Spongiform Encephalopathy (TSE, "scrapie"), Alzheimer's, autism, and other progressive neurological disorders.

One especially intriguing similarity is the kind of polymorphic amyloid fibrils found in the brains of individuals damaged by these diseases.

These tangles of disruptive proteins, sometimes referred to as 'plaque', are markers for these diseases.

• Mercury can induce fibril tangles.

• Hexane can induce fibril tangles.

• Pesticides can induce fibril tangles.

• Metals and pesticides have been seen to act synergistically towards the formation of tangles.

No infectious agent (virus, bacteria, parasite) has been identified as the cause of BSE/TSE.

Much focus has been placed on the notion of 'prions' as the agent causing BSE/TSE and also vCJD.

A prion is defined as 'an abnormal form of a normal protein'.

But instead of looking at prions as the cause, it makes more sense to look at prions as the result.

The reasonable cause is chronic accumulations of hexane, mercury, and other chemicals working synergistically to cause oxidative stress, nerve degeneration, gene morphisms, misfolded or unfolded proteins, and other effects.

Interestingly, BSE/TSE does not occur in herds that are organically ranged and fed.

One reason hexane may have been overlooked as a causative agent is that it is used universally for extraction — including for research experiments.

If hexane is a causative agent, its signal will be lost or distorted when more hexane is added during laboratory set-up and analysis.

Think this is all a bit far-fetched?

Here is a grass-roots letter by an Indiana cattle-producer.

He noticed more animals got sick, had birth defects, had miscarriages, or died when eating pellet meal.

But not when they ate green grass.

He started looking for answers.

And discovered the pellets contained hexane residue.

Hexane is used in the extraction of oil from algae.

The oil is then used as an ingredient in infant formula.

There is research into non-hexane processes, but it will be years until any viable processes replace the existing hexane process for widescale production.

The capital expenditures for re-tooling will be significant and this will further slow adoption.