“All happy families are alike; each unhappy family is unhappy in its own way.” — Leo Tolstoy, in Anna Karenina
I once worked with a facility that discharged process equipment cleaning water to the city sewer. They had a tough time staying below the discharge limits for copper. In turned out that the city water was coming to them with copper levels that already exceeded the discharge limits.
Addressing contaminants requires a good understanding of the source of those contaminants.
Contaminants in Process Safety
When we lead a PHA in the form of HazOp, we use a standard list of deviations. Even though we know that there are few nodes to which every deviation will apply, we look at them all. This helps to avoid inadvertently overlooking a hazard.
Three of the deviations are under the general heading of composition. “High” refers to something that is supposed to be or is normally present but is unsafe if there is too much. “Low/no” refers to something that is supposed to be present but creates a hazard if there is not enough. “Other than” refers to contaminants, something that should not be present but could be and is unsafe when it exceeds certain limits.
In truth, PHA teams will sometimes struggle to distinguish between high composition and contaminants, but the taxonomy of the hazards isn’t the point; identifying the hazards is the point. Upon identifying a hazard, the PHA team will try to recommend measures to reduce the risk of the hazard, either by preventing the introduction of the contaminant into the process or by removing the contaminant once it is present.
Product Safety vs. Process Safety
The pursuit of product safety differs from the pursuit of process safety. The ultimate objective of process safety is to identify the hazards of the process and then to protect workers, the community, and the environment from the hazards of the process. The ultimate objective of product safety is to identify the hazards of the product and then to protect consumers from those product hazards. The two pursuits are not the same, but when it comes to the hazards associated with contaminants, the same tools apply.
The Source of Contaminants
Contaminants have three types of sources.
The first source of product contamination is from contamination of an input to the process. A contaminated raw material can lead to contamination of the final product when the contaminant is carried through the process.
The second source of product contamination is from contamination by the process equipment. Corrosion, for instance, does not only lead to loss of containment, but can also lead to product contamination.
The third source of product contamination is from the process itself, where the process creates the contaminant, typically as a byproduct of the intended reaction.
Spirits Distillation – An Example
In their 2024 paper on beverage alcohol product, “Substances of health concern in home-distilled and commercial alcohols from Texas”, the authors identified four contaminants of concern in spirits production: copper, lead, glyphosate, and methanol. All three types of sources play a role in at least one of these four contaminants.
Copper: In the U.S., the maximum allowed concentration of copper in drinking water is 1.3 mg/liter; in wine, it is 0.5 mg/liter. Given distillers’ preference for copper stills and other equipment, one would anticipate copper to be extracted from the process equipment. In fact, the authors did not detect copper (detection limit of 0.03 mg/liter) in 31 of 36 samples of home-distilled spirits and did not detect copper in 10 of 12 samples of commercially produced spirits. Of the seven samples with detectable levels of copper, four exceeded the FDA’s limit for copper in wine.
For most spirits producers, then, copper in the final product is not a problem.
When it is a problem, the absence of copper in the vast majority of samples suggests that it is not inherent to the process equipment. Copper is not volatile, so there is also no reason to believe that copper in the mash water carries over from the distillation. That leaves copper in the proofing water that is added after distillation. Before undertaking modifications to eliminate copper leaching from process equipment, it would make sense to first determine whether the proofing water contains copper to begin with, and if so, remove it with something like ion exchange.
Lead: Lead poisoning is familiar to us all; the limit in drinking water is 0.015 mg/liter. While many municipalities are working to replace the lead piping in their city water distribution system, there are still instances of lead-contaminated city water at specific locations. Another source of lead, however, particularly in older equipment, is lead in the solder used to assemble the still and other copper process equipment. Fortunately, the EPA banned the use of lead in solder in 1986, so new equipment should not pose this hazard.
In their study of spirits production in Texas, the authors did not detect lead in 23 of 36 samples of home-distilled spirits and did not detect lead in 8 of 12 samples of commercially produced spirits. Unfortunately, their detection limit was 0.11 mg/liter, 7 times higher than the EPA limit. Therefore, it is possible that every sample contained more lead than drinking water is allowed to contain. Fully a third of the samples, however, whether home-distilled or commercial, contained unequivocally detectable levels of lead, at an average of 0.54 mg/liter.
Like copper, lead is not volatile, so it would not have distilled over from the mash. Were the lead-contaminated samples from older equipment constructed with lead-based solder? Or was the lead in the proofing water? Those are hazards that warrant additional study.
Glyphosate: Glyphosate is the broad-spectrum herbicide widely used in the production of agricultural crops and a suspected carcinogen. The most commonly recognized brand is Monsanto’s Roundup. Crops frequently contaminated with glyphosate include grains, e.g., corn, wheat, and oats, as well as fruits, nuts, and legumes. Glyphosate enters the spirits production process as a contaminant of the raw materials. It is not extracted from the process equipment, nor is it created during the process.
Fortunately, glyphosate is not volatile, so it does not carry over during distillation. When it is present in the raw materials, it concentrates in the still bottoms, or “pot ale” as it is sometimes called. We would not expect to find glyphosate in finished product unless the still bottoms are added back to the distillate for the purpose of diluting—proofing.
It should come as no surprise, then, that the study authors only detected glyphosate in two samples of spirits, both home-distilled. Their detection limit was 0.075 micrograms per liter, compared to the EPA limit on potable water of 700 micrograms per liter. As long as still bottoms are not used for proofing, then, glyphosate in finished spirits is not a hazard that needs to concern distillers.
Methanol: In addition to ethanol, fermentation converts sugars into several other organic compounds, chief among them being methanol, which is toxic. This is well known among distillers, who rely on the difference in boiling points between methanol (BP = 148.5°F, 64.7 C) and ethanol (BP = 173.1°F, 78.4 C) to separate the “head cuts” from the “heart cuts”. The separation is not sharp, however, and flavor compounds are also involved, so most spirits contain some methanol. Deciding where to make the cut between heads and hearts is part of the art of distilling spirits.
Of the 12 commercial samples tested in the study, all contained methanol, ranging from 0.2% MBV (percent methanol by volume) to 1.5% MBV. Thirty-one of the 36 home-distilled samples contained methanol, ranging from 0.1% MBV to 2.2% MBV. Interestingly, five of the home-distilled samples contained no detectable level of methanol (detection limit of 0.006% MBV), meaning that those five home-distillers took very late heart cuts to avoid contaminating their spirits with methanol.
Note how important the distillation step is to removing, or at least controlling, contaminants in the production of spirits. It is interesting that brewing beer has the same vulnerabilities to contamination, but not the advantage of distillation, which removes impurities.
Each Contaminated Product Is Contaminated In Its Own Way
Every organization has finite resources, so it is essential that those resources be deployed wisely. Spending effort on speculative hazards that have little impact, or on mitigation strategies that don’t actually address the hazards is a waste of those resources.
Each process and product has contamination issues that are specific to the process and its products. Understanding the sources of contamination is the first step in controlling the hazard of contaminants, of managing the likelihood and consequence severity of their presence. It is only by managing the likelihood and consequence severity of the presence of contaminants that the risk can be limited to something that is tolerable. In the case of distilled spirits, the risk is a product safety risk to consumers. The same principles, however, apply to process safety risks to workers, community, and the environment.
