No. This functionality isn't available at all.
Due to how reCAPTCHA works:
1) One word is known. I would hope that these words are pre-filtered for potentially 'profanitory' words.
2) The other word isn't actually known to the system (well technically. Each unknown is used more than once, and I'd assume if a substantial number of people enter the same profanity for a particular image, it would be subject to the same filter above) - this is the whole point of reCAPTCHA, and thus cannot actually be filtered.
Additionally (due to point #2) it's rather impossible to guard against rather unfortunate nature of the occasional phrasing that ends up on some humour sites.
I presume it's profanity you're asking to block. If you have your own list of other words you want to block, then certainly, no. There is no facility, paid or otherwise, to filter what's presented.
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PJH