Mixed evidence that nearby CAFOs make people sicker

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CAFOs pollute local air with more than just foul odors: they release bacteria, fungi, endotoxins, ammonia, hydrogen sulfide, methane and even antibiotic residue into the air. Local communities breathe all this in.

In Mexico, there have been resident reports of respiratory health issues due to hog pollution in the Perote Valley area, and governmental investigations found decreased aquifer levels, increased odors, and poor air quality due to swine farms in that region.
A study of followed 4M rural Dutch (Simões et al., 2022) between 2005 and 2012 and found that 54.5% lived within 500M of an animal farm, 98.8% within 2KM. Living near pig farms increase mortality risk from Respiratory disease and Pneumonia, being close to dairy farms had no effect and being close to poultry farms but only when they were intensive.
A systematic review by Perry (2024) of 12 studies between 2015 and 2023 on health outcomes of living near poultry CAFOs finds 9 of them (75%) find negative health effects. 5 of the 8 studies that investigated respiratory problems found negative effects
A systematic review by Douglas et al., 2018
Pig cafos, but not poultry cafos can increase urinary tract infections though E-Coli
Shultz 2019 found that asthma was 1.9 times higher in populations living within 1-2 miles of a dairy/beef CAFO (1.6-3.2) in the US, lifetime chances of an asthma diagnosis were 2.67 times higher if they lived 1.5 miles from a CAFO. Nearly all of these were Dairy or beef CAFOs.
Baliatsas et al., 2020 significantly higher prevalence of pneumonia in the total sample in the livestock dense area, which was also observed among susceptible subgroups of children, the elderly, and patients with chronic obstructive pulmonary disease (COPD). Lower respiratory tract infections, respiratory symptoms, vertigo, and depression were also more common in the livestock dense area compared to the control area. In general, there were no significant differences in chronic conditions such as asthma, COPD, or lung cancer.
Hooiveld et al, 2015 found that greater odor annoyance from living near a CAFO, the more participants self reported various symptoms, though they rarely visited their doctor about them.
A systematic review by O'Connor et al., 2017 found no consistent evidence that proximity to farms reduces health.
Systematic review shows that CAFOs (and other industrial plants) that give off bad odors can cause headaches, nausea, vomiting and such

Smells

Caffyn 2021 details the smells that come from CAFOs in Herefordshire and Shropshire

Most health effect are respiratory

the 2024 poultry review, 9/12 focussed on respiratory, with 6 of them exclusively studying resp.
This systematic review by O'Connor 2017 also mentions that respiratory are the key issues.

Case Study, North Carolina

In North Carolina, poorer communities with more people of colour are more likely to be closer to swine CAFOs. They're often too poor to move. The state 8.8 million pigs produce 10 billion gallons of waste a year.

Complications

Rural populations have less pollution so generally have lower rates of respiratory disease, which may mask the effect of CAFOs, so looking at CAFOs.
Studies at 1 point in time might be confounded by the fact that people who have terrible health effects from CAFOs will typically just move away, only leaving those with decent health. This might misleadingly create the impression that there are no negative health effects, when its actually because the study selects for healthier people who can tolerate the effects.