Poor cognition was categorized as scores equal to or less than 15.
Feeling equal power Less than one-third of the statements related to autonomy were categorized as feeling in an equal position or having equal power.
Distance to nearest facility was calculated for each set of birth record coordinates and categorized as less than or equal to 2.5 km, less than or equal to 5.0 km, between 2.5 and 5 km, or greater than 5.0 km.
Total PCBs were categorized as greater than or equal to versus below the median, on the basis of the distribution in African American or white controls separately.
Economic hardships was categorized as 'none' (if the sum was equal to zero), 'mild' (if the sum was equal to one), 'severe' (if the sum was equal to two) and 'very severe' (if the sum was equal to three).
Material deprivation was categorized as present if the sum was equal to zero or one and not present if the sum was equal to two or three.
Symptoms were then categorized as mild (score less than or equal to six), moderate (score of seven to twelve) and severe [score greater than twelve, or when one symptom was considered incapacitating every day (score = 9)].
The words were then categorized as: low frequency defined as less than or equal to 50 words per million, medium frequency defined as 51 100 words per million, or high frequency defined as 100+ words per million.
These values resulted in approximately equal numbers of cases being categorized as medium and high priority.
