Don't mean to disagree with anyone, and while I totally agree there is a lot of misinformation, bad reporting, and in some cases overreactions on certain aspects, I believe there are a few things to keep an eye on. I was a firefighter/medic for 27yrs, and most of those years I was a member of our county's HazMat response team, trained as a hazardous materials 1st in technician. I may not have the scholastic pedigree of seasoned scientists (but I do have mad respect for what they do) but we had quite of bit of extra training to be on the team, classroom and in the big scary looking hazmat suit..lol, so I'm just going to throw my two cents in if you don't mind, and give you a bunch of links so you can do some of your own research.

So I'm in the St. Louis area, which is about 50miles further than you are from the incident I believe and I'm leaning towards the optimistic side of being concerned, granted the Ohio river does empty into the Mississippi river not too far from me. For two main reasons...one is that vinyl chloride is by far not the only chemical release they had, although it does pose the greatest risk, and is what the media seems to be focused on, there are a few others of some concern. Secondly, most people are using the EPA to get their information from and are the lead organization on the investigation. Now the EPA are excellent at providing information on an incident like this, during and the immediate aftermath for several weeks, but for long term consequences, and this part here is more my opinion from past experience, seem to be more concerned, or maybe equally concerned, at getting back to "normal' and squashing any fears of long term issues that paint the incident in any more of a bad light. I feel this way because the leadership of the organization has become a little too political for my taste in the recent past, and also this letter here to Norfolk Southern Railroad, that they made very public, very quickly, that spells out in detail, the responsibility of any and all negative events or outcomes resulting from this incident solely lies at the feet of Norfolk Southern Railroad. I'm guessing so if people or animals start dropping dead, regardless if it's because the EPA gave the green light for people to return home, or businesses to reopen, they won't get blamed for it. Letter from EPA to Railroad

This is not my opinion, this is a given, we WILL see long term consequences to our environment for years to come, the scope and severity of which I am not certain at this time, but they will occur. The chemicals that should also be at least mentioned by more media are of less concern than vinyl chloride, but these, which I found with a little help from a former colleague still on the job, I want to mentions. I got it from this, it's a bill of laden of sorts, from Norfolk Southern Railroad to the EPA I believe, not anything secret, I found it on the internet, just needed some help finding it. The green, orange and yellow boxes that are completely highlighted were done so by the railroad or the creator of the document, the red, purple and brown areas that are circled, I did, to simplify it a bit more. ( I will also use this for a future training class with my former department in which I still attend once in a while). The Chemicals they have highlighted green are the ones they are concerned most about, and match up with the ones that concerned me the most, after reading about a list of possible chemicals in another story about the incident. Bill of Lading

Ok, while the media and our geologist covered vinyl chloride accurately and you're aware of it, the other chemical other than that one, which gave me the most concern, was Ethylene Glycol Monobutyl Ether, say that three times fast, right? So what concerned me about this one is that it's got the most information available about chronic, or long term, effects. A lot of the information available online about everyday chemicals we use, especially MSDS (material safety data sheets) made my the manufacturer of the chemical(s) have a very small section about chronic effects, they won't even use the verbiage "long term". Often the these sections have a lot of the phrase "no valid information at this time", which is good and bad, because there's always studies and papers being done by scientists, organizations, and companies, and while there my be a plethora of them to read through, often they are not peer reviewed or substantiated by any credible journals, and if everyone were included on MSDS forms, it could make them unreliable. At the same time, practically needs to be handed down by a royal figure before it will be accepted into the MSDS, so if you do see anything listed in that chronic effects section, it's something you should at least pay attention to for a while if you've been exposed, and this chemical had more than your average chronic effects. Here is very detailed, and yes boring, data sheet on everything you'd want to know about this chemical EGME data sheet Here is an official complaint, I guess, to the U.S. Federal Registry about this chemical, so obviously it's been an issue with the environment and our safety in the past Community Complaint

This one concerned be due to an odd lack of information I was able to dig up on it, and because of an abundance of links I found about this chemical, R Butyl Acrylates, Stabilized, being involved in several environmental concerns in Great Lakes NY. I didn't have time to dig into it further, but here is a link to a search result with lots of stories on it Great Lakes NY stories

This last one, Isobutylene, is fairly harmless, but with long term or frequent exposure, or by mixing with other chemicals it can result in a type of benzene that is the chemical at the center of the bad water at Camp Lejeune, that has all the military vets dying and a big law suite going on. Data sheet Camp Lejeune article

Let me wrap up by saying, again, I am not disputing mrsgeolotigst at all, the info she gave about the that specific chemical and the chances of it harming you in the DC area (btw, I don't think many outside DC know what DMV stands for, took me 20min on google to figure it out..lol) I'm only adding that there could be further concerns beyond the scope of her response, as far as acute danger, you are all fine, long term you're most likely going to be just fine too, I did read that Maryland and Virginian already have testing up and running for water, and are being extremely pro active about monitoring water and air for their respective states. The environmental impacts will that I'm more certain of will most likely occur closer to the incident sight, and far reaching somewhere down river, or the ocean, that will be subtle at first but add to the list of things we humans have messed up with mother nature. Here's some helpful links if you want to research further, that you don't have to be a scientist to understand most of what they offer.

NIOSH has a guide book that is in the holy trinity of resources when it comes to HazMat NIOSH website,

Another CDC organization, but this time they deal with prevention, action plans, community based actions to an incident, rather than focusing on the chemicals themselves. ATSDR

This last one despite being around a long time, I just learned about in the last year or so, and really like that it's an international organization, of scientists, especially chemists, that pool information, and just have tons of resources, news and more at their website C&EN