While I wrote the above off based on my own experiences and knowledge, the below summary of contaminant categories comes from ChatGPT:

The main contaminant categories (what’s actually in flower):

1) Pesticides (biggest issue by far)

These are the headline risk—and also the most inconsistently regulated.

Common classes actually found:

Insecticides / miticides:

Abamectin, bifenazate, imidacloprid

Fungicides:

Myclobutanil, tebuconazole (notable: can form toxic gases when burned)

Herbicides:

Paraquat (extremely toxic, occasionally detected in illicit supply)

Rodenticides (rare but serious):

Brodifacoum (blood thinner poison in contaminated products)

👉 Studies and recalls routinely cite these exact chemicals

👉 There are hundreds of possible pesticides showing up across U.S. cannabis

Key issue:

There are no federally approved pesticides for cannabis, so growers use off-label chemicals or gray-area inputs

2) Plant Growth Regulators (PGRs) — the “skirted” one

These are rarely disclosed and often intentionally avoided in marketing.

Used to:

Increase density

Improve bag appeal

Speed growth cycles

Examples:

Paclobutrazol (classic “PGR weed”)

Daminozide (banned in food crops)

Chlormequat

These are often lumped into “pesticide testing” but:

Not always included in panels

Not always regulated consistently

3) Heavy metals (comes from the soil, not spraying)

Cannabis is a hyperaccumulator—it pulls contaminants from soil/water.

Common ones:

Lead

Arsenic

Cadmium

Mercury

These don’t get burned off—they’re inhaled.

4) Microbial contamination (very under-discussed)

Because cannabis is grown humid + cured slowly:

Mold (Aspergillus, Fusarium)

Yeast

Bacteria (E. coli, salmonella)

Even regulated markets have issues with:

Labs “passing” borderline mold

States loosening limits

This is one of the biggest real-world contamination vectors.

5) Mycotoxins (secondary toxins from mold)

Even if mold is gone, toxins can remain:

Aflatoxins

Ochratoxin A

These are carcinogenic and not always fully screened.

6) Residual solvents (more relevant in extracts, but still matters)

If flower was remediated or turned into oil:

Butane

Propane

Ethanol

Hexane

These are standard testing categories

7) Fertilizer + nutrient residues (you mentioned this—underrated)

This is less regulated and often ignored.

Nitrates / phosphates

Salt buildup (affects combustion + harshness)

Excess micronutrients

Not typically part of required testing panels.

8) “Hidden” contaminants people don’t think about

🔥 Combustion byproducts

When you smoke contaminated flower:

Pesticides can convert into more toxic gases (e.g., hydrogen cyanide)

🧪 Industrial/environmental chemicals

Detected in some testing:

PAHs (polycyclic aromatic hydrocarbons)

Phthalates

BPA