How to add data elements to form_dropdown()

Hi,

Is it possible to include additional data elements to the option tag using the form_dropdown helper?

For example I would like to achieve something like below. I've not seen anything in the documentation or the support forum, so not sure if this is possible.

Thanks.

Code:

<select name="day_of_week" id="day_label" value="">
    <option value="Monday" data-rel="1">Monday</option>
    <option value="Tuesday" data-rel="2">Tuesday</option>
    <option value="Wednesday" data-rel="3">Wednesday</option>
    <option value="Thursday" data-rel="4">Thursday</option>
    <option value="Friday" data-rel="5">Friday</option>
    <option value="Saturday" data-rel="6">Saturday</option>
    <option value="Sunday" data-rel="7">Sunday</option>
</select>