What health concerns are there for a one-year-old that played in dog urine?

Some: Urine is 95% water and 5% discarded materials. The risk is playing in old urine as it breaks down in time and promotes bacterial growth. Pets are often a positive influence in a child's life but can pose some health hazards. Caring well for both your pet and children can keep this relation healthier for all. http://www.aafp.org/afp/2007/1101/p1314.html