As previously discussed, the TSCA is used to cover nanotechnology products. This is how it may actually work in practice:

In August, BNA (Bureau of National Affairs) reported in its Daily Environment Report that it had asked EPA to explain the agency's review of nanoscale chemicals under the Toxic Substances Control Act (TSCA) following a notice in the Federal Register that an un-named company would begin manufacturing siloxane-coated alumina nanoparticles. According to EPA officials, only one nano-chemical reviewed by the agency exhibited novel properties of concern to regulators.

That means, nanoproducts may not be perfectly "filtered" through TSCA review. An ETC member said:

"The government hasn't even agreed on standards for measuring or otherwise characterizing nanoparticles and the EPA has neither the tools nor the expertise to evaluate them. Nanotech companies are telling patent examiners and venture capitalists that they are taking advantage of nanoscale, quantum effects to create novel materials while telling the EPA that these chemicals are just the same-old, same-old."

I am not sure on what he meant by quantum effect. But, it signifies that nanoproduct could be masked as "the same old chemicals". As far as I know TSCA does not make any nano-distinction. It's a chemical regulation after all:

EPA's Jim Alwood told ETC Group that the agency doesn't keep a running tab on whether or not chemicals are manufactured on the nanoscale, making it very difficult to estimate how many nanoscale chemicals are in production.

And, it doesn't seem that they are taking precautionary approach:

Groundless groundwater experimentation: In addition to paving the way for companies to produce and commercialize nanoscale chemicals, EPA is actively contributing to the release of engineered nanomaterials in the environment. In January, the agency announced a plan to clean up the Nease Chemical Superfund site in the state of Ohio by injecting "nanoscale zero-valent iron" (NZVI) into the groundwater.