Meet The Big Four Weed Killers

Roundup, Atrizine, Resicore, and Status. These herbicide make sure that (broadleaf weeds and grasses, especially) we have plenty of vegetables at a reasonable price, and there is still plenty of veggies left to export.

Roundup is Glyphosate:

This herbicide's PO3H group with the NH part may easily cause errors in the phosphate rich environment of the DNA-RNA and its transcription. Nucleotides have the same PO3 terminus:

But I still have to find research papers studying this effect. 

Hopefully this chemical's water solubility means it could be washed nearly completely, and if there are any residues managing to enter an organism, then ultimately the error checking RNA mechanisms would overcome it, as they overcome these challenges daily.

Atrazine:

One positive thing going for this herbicide is that many bacteria easily though slowly biodegrade it.

The molecule itself once it reaches the cellular nucleus might be mistaken for a pyrimidine, a crucial part of the DNA and RNA code. The Chloride atom may easily wreak havoc with transcription.

by BruceBlausen

Let's hope our chromosomes have a good programs running all the time and check our genetic code for errors.

Resicore 

It is something new, designed by Dow Chemicals to counteract herbicide resistance, and is comprised of three unique herbicides, which have interesting commercial names (from this Iowa State University paper):

Acetochlor, a.k.a.Surpass

In plants it inhibits enzyme that builds, or elongates fatty acids. This process is a crucial to all life animal or vegetable.

Mesotrione, a.k.a. Callisto, 

This molecule is a somewhat natural inhibitor of an enzyme that builds carotene, which protects chlorophyll from being degraded by sunlight.

Any damage to the production of this enyzme (4-Hydroxyphenylpyruvate dioxygenase, HPPD) can be linked to one of the oldest known inherited metabolic disorders known as alkaptonuria in humans.

Alkaptonuria is a rare inherited genetic disorder in which the body cannot process the amino acids phenylalanine and tyrosine, which occur in protein.

It is possible to imagine that the molecule once inside the cellular nucleus, might have its acidic SO2 group pose as the acidic PO3 group of nucleotides. The rest of the molecule presents enough capability to obstruct the DNA/RNA transcriptions by both its spatial dimensions and interatomic affinities for the correct nucleobases. 

and sometimes substitued by Flumetsulam, a.k.a. Python, which is

the molecule already resembles these building blocks of genetic material

and looks as if Guanine is coupled to any of the pyrimidines, U, T or C.Except the herbicide molecule does not need to fix itself into the nucleotide's place in the DNA helix. it might just float there, obstructing transcription, and preventing either growth, or promoting death outright.

and, 

Clopyralid, a.k.a. Stinger

It is particularly damaging to peas, tomatoes and sunflowers and can render potatoes, lettuce and spinach inedible. Being a benzoic acid due to the -OOH group, it is rendered rather water soluble, and neutral to mammal organisms, but theoretically having the -N- nitrogen in the ring, it is a pyridinecarboxylic acid, and again theoretically, could masquerade is pyrimidine, which it does in many plants, and does it successfully.

The fourth biggie is Status, 

It is a mixture of sodium salt of Diflufenzopyr, 

Diflufenzopyr is an auxin-transport inhibitor that can increase the phytotoxicity of certain auxin-mimicking herbicides such as Dicamba (see below) on broadleaf species. Auxin is a plant hormone which causes the elongation of cells in shoots and is involved in regulating plant growth. Auxin is produced in the apex of growing stems.
Being in the Sodium (Na+) salt state, it is relatively water soluble, and should be easily broken up by the gut bacteria, or jsut ignored and passed through human body. Theoretically, the overall structure of this molecule resembles a guanidine-pyrimidine pair.

and Dicamba. 

The OOH is what makes the molecule a carboxylic acid, just like Chlopyralid, and water-soluble too. The herbicide is very selective and efficient. It has not been shown to affect mammals. The only controversy it did cause what transferring to and poisoning compost, which instead of fertilizing tomato gardens, killed them off.
To comment on possible interaction with human metabolism, the molecule is most likely to be treated as a benzoic acid, which is also found in cranberries, accept the Chloride groups and the methoxy group (-OCH3) theoretically would steer it down the PCB disassembly pathway.

These last two herbicides should present no danger as long as vegetables are washed with plenty of water.