Modern concentrated animal feeding operations generate sizeable amounts of manure and related emissions into water and air. These present potential harm to human health. Adverse respiratory effects have been documented among workers in these feeding operations, but there has been little research on wider environmental effects. Few conclusions are possible at this time but recent studies (including a report in this issue of Epidemiology by Radon and colleagues) suggest possible adverse effects. Respiratory outcomes of greatest concern include nasal allergies, airflow obstruction and asthma. Another concern among residents near concentrated animal feeding operations is adverse effects from malodors. The potential impact of these operations on quality of life and health needs to be documented.