Copper and lead solder were used for centuries, so I'm not sure how you can get too much lead or other metals unless you're using lead tubing or strange alloy containers somewhere.
As usual, there are problems with distilling inherent to the process that can cause issues. And the home distillers are not going to be knowledgeable or quite as concerned about the process since they are not going through the FDA or OSHA so their cleanliness and equipment standards may slip a little with no presssure being applied.
Methanol:
Produced in small amounts during fermentation—especially when using high-pectin fruits (like apples, plums, or grapes). While normal fermentation levels are low, distillation concentrates both ethanol and methanol, making early-run liquids (foreshots) a toxic risk that can cause optic nerve damage or blindness if ingested.
Ethyl Carbamate:
A harmful compound that can form from hydrogen cyanide during the processing of certain fruit-based mashes and stone-fruit kernels.
Copper Corrosion:
While copper is commonly used because it removes sulfur compounds, excessive corrosion from high temperatures and low pH washes can leach copper into the distillate, causing nausea, neurological damage, or renal issues if consumed in high amounts.
Agricultural Pesticides and Glyphosate:
Using unwashed fruits or grains treated with weedkillers or insecticides can introduce toxic residues into the mash.
Unfiltered Water Sources:
Adjusting the proof or dilution of spirits with untreated or contaminated local water can introduce heavy metals or chemical pollutants.
Improper Sanitation or Chemicals:
Using non-food-grade plastics, chemical cleaners, or industrial solvents (such as diesel fuel or unapproved denaturants) creates severe poisoning risks.
There are so many things that can go wrong in an honest effort to do it right it is very easy to have a problem. The people doing this are most likely not trained and probably don’t have all the equipment to full fill all the steps that major distillers use as they are just a little guy/gal+ trying to make something many cases for fun. We have stores to buy distilling equipment over the counter retail in my area. An since most of the lead contqmination comes from the pipes under your house, that creates a problem if you don’t use bottled water. A lot of it. It takes approximately 37 liters of water to end up with 1 liter of product. So it takes just under 10 gallons of water to produce 1/3 of a gallon.
wy69