Straw and hay bale poison

I would love to use straw, or even hay in some applications in my garden.  But I can't find organic straw or hay in my area, so I worry about what I can get. Most of the places that sell it, including the co-op I work for, don't have a clue what chemicals were used in the growing process.  I also try to tell customers who I know are going to use it for growing food to be careful. Today I was doing just that, and of course the customer was concerned. The man behind her told her not to worry. The straw/hay sold in California is safe to use to grow food. She was happy bought the hay. The man told me it's his business. I so wish I could remember the exact words he used, but I just can't. At the end of the conversation I didn't feel like he said there wasn't a broadleaf herbicide used, but what is used has no residual effects  80 days after the farmers spray.
I work for a Co-op, I only have a short time with the customer, and I must be careful what and how I say things. Anyway I'm not sure if the man was a farmer, or works for big AG?  I don't pretend to know everything, far from it. I didn't appreciate the jist of his conversation with the other customer, which was there there little lady you'll be fine the dumb cashier doesn't know what she's talking about.  I can deal with the attitude.  
I do like the learn, and share accurate information, and I trust the intelligent and amazing people of permies, more than an unknown farmer/ Big AG guy.  So is it a real concern, or useless worries?  Is there truly 0 residual chemicals after 80 days?
Thanks everyone.

Jen, that's a lousy situation. You should not be put on the spot like that. Kick this question upstairs --- your co-op people need to give you data, so you can be honest about what you are selling. Otherwise, employ the three most intelligent words in the English language -- "I don't know."

I have opinions on this subject, and I have methods to process this category of biomass that I think are effective, but I am not inclined to post my thoughts here. These conversations get stomped on heavily, per the publishing rules. This is Cider Press territory.

I have always had a tough time deciding where to put a post, so feel free to change what you like.
I have asked management what chemicals are used on the hay/straw and I'm told it comes from different companies and they don't know.
Maybe I'm asking to much. I wasn't looking for a debate on chemicals, big AG, or any of that. I just wanted to know if it's safe to use in my garden knowing only the information I shared with you.  
Thanks for responding.

It's a difficult topic. I wish I could offer easy answers, but I don't think there are any.

I moved this to cider press, it's a great question.
Do remember, cider press you can talk about things, but still MUST be nice!!

I'm wondering, even if there is an herbicide that breaks down that fast,
A) how do you know that's what's been used?
and
B) What does it break down into?

I really wish that if chemicals were used, they had to tell you what they were, as well as what the breakdown products are. I'm glad that you're encouraging the co-op customers to think about these things, Jen. Some of those herbicides could decimate a garden. Not to mention, people should be able to find out what is going into/on their food when they're growing it themselves. I think you're awesome for trying to learn more about this so you can share that information.

I share your concerns and would doubt there aren't any residual chemicals after 80 days, but I don't know for sure. I don't know if there's a way you could determine what was used. You certainly could determine if there was enough residual chemical to be harmful to plants by doing a bioassay. Of course, even if there wasn't enough to harm plants, there'd be no way to know if it was harmful to soil life, people, etc that I'm aware of (short of having access to a lab). So the test would only give you limited information, but perhaps a slightly clearer picture? There's also the possibility that it isn't always the same chemicals in every batch of straw or hay.

As I have tried straw bale gardening and had my plants do horribly I think it's safe to say the pesticides stick around long after the man said they do. Jill Winger @ The Prairie Homestead also had the problem of poisoned hay killing her garden.

It is specifically the aminopyralid class of pesticides that stick around for years and kill or damage broadleaf plants. They may be found in hay, straw and manure of grass-eaters, because they do not kill the grass family of plants.