No veo que existan tablas que tengan campos que referencien a esas tablas.
Podes consultar con lo siguiente:
select conname as "Foreign Key",
t1.relname as "Tabla que referencia",
a1.attname as "Columna que referencia",
t2.relname as "Tabla referenciada",
a2.attname as "Columna referenciada"
from pg_constraint as c,
pg_class as t1,
pg_class as t2,
pg_attribute as a1,
pg_attribute as a2
where t2.relname in ('mdp_actividad_economica_subsector','mdp_actividad_economica_sector', 'mdp_empresas') --> tablas_referenciadas
-- and a2.attname = 'columna_referenciada'
-- and a2.attname <> a1.attname -- Para ver las referencias con nombres diferentes en las columnas relacionadas.
and c.conrelid = t1.relfilenode
and t2.relfilenode = c.confrelid
and a1.attrelid = t1.relfilenode
and a2.attrelid = t2.relfilenode
AND (
( c.conkey[1] = a1.attnum AND c.confkey[1] = a2.attnum ) OR
( c.conkey[2] = a1.attnum AND c.confkey[2] = a2.attnum ) OR
( c.conkey[3] = a1.attnum AND c.confkey[3] = a2.attnum ) OR
( c.conkey[4] = a1.attnum AND c.confkey[4] = a2.attnum ) OR
( c.conkey[5] = a1.attnum AND c.confkey[5] = a2.attnum ) OR
( c.conkey[6] = a1.attnum AND c.confkey[6] = a2.attnum ) OR
( c.conkey[7] = a1.attnum AND c.confkey[7] = a2.attnum ) OR
( c.conkey[8] = a1.attnum AND c.confkey[8] = a2.attnum ) OR
( c.conkey[9] = a1.attnum AND c.confkey[9] = a2.attnum ) OR
( c.conkey[10] = a1.attnum AND c.confkey[10] = a2.attnum )
)
order by 2;
Seguimos buscando y cualquier novedad te avisamos.