Using the same search parameters - (city & the words "water pollution, cancer and kidney failure" one at a time) - here are results for Oaxaca and Puerto Vallarta, two very popular destinations and expat relocation cities.
A long post but an easy and quick read!
Oaxaca, Mexico
The state of Oaxaca has a significant coastline on the Pacific Ocean. The state is best known for its indigenous peoples and cultures.
The state of Oaxaca has the third lowest drinking-water coverage (79 percent) after Chiapas and Guerrero, and the lowest sanitation coverage (71 percent) in the country. This contrasts with the high level of availability of water resources in Oaxaca, the state with the fifth biggest groundwater reserve in the country.
Increasing population with ever higher demands for water, more cement constructions and paved streets, cutting down of forests, water pollution, a lack of water treatment plants and water infrastructure, a lack of environmental laws and law enforcement, and the illegal drilling of wells are just some of the most pressing problems.
Rainfall patterns have changed over the last 20 years. There are now more severe and longer periods of drought;
Water in Oaxaca City used to be plentiful. The city is located in a valley surrounded by mountains. Two major rivers were flowing through the valley, the Atoyac and the Jalatlaco. The latter- was severely contaminated in the mid-19th century by a flourishing leather industry. What’s left of this river now flows underground. It has been paved over. Where there once was a river, where people bathed and washed their clothes, there is now a busy street. Some of the side streets of the neighborhood are still paved with stones from the lost river.
An increase in sewage, traffic, throw-away products, and urban extension contaminate much of what is left of the life-giving water in Oaxaca City.
Source: Water in Oaxaca, Mexico
Saturday, September 7, 2018 . The earthquake, which struck at 11:49pm with an epicenter off the coast of Chiapas - a year after the powerful earthquake that devastated parts of southern Mexico, the mayor of one of the hardest hit towns said that the situation remains “critical” and called on the federal government to allocate more funding to reconstruction.
Drinking water in Oaxaca
"The water pipes in the city system have leaks and dirt and god-knows-what can seep in since they are not under continual pressure." Anonymous resident
Visitors to Oaxaca should not be afraid to drink water in restaurants, avoid ice, or shun produce. In fact even street fare can be enjoyed. This is not medical advice, but merely an opinion designed to assist vacationers to the city. Do exercise caution since Mexico is third world, where health and cleanliness standards are often different than those in the west.
Source: Dining and Indulging Do's and Don'ts (Tips)
Puerto Vallarta
Puerto Vallarta is one of Mexico's premier beach towns and a very popular destination spot for travelers worldwide.
Finally some very good news about the water in Mexico!
When researching water pollution/contamination in Puerto Vallarta I did not find any of the many ongoing contamination issues that I found in the other 4 cities.
The only incident I found happened recently, and as happens in Mexico - the local officials tried to cover it up so as not to impact holiday tourism --
During the high season and holidays the west coast of Mexico in general, suffers from an overload of their sewage treatment infrastructure.
March 2019 -
The rupture of a sewage collector contaminated the beaches, for which the Secretary of Health of Jalisco asked not to use the beaches or consume shellfish or raw fish.
Authorities decreed sanitary and environmental warning in the municipality of Puerto Vallarta, Jalisco , after the rupture of the Central-North collector, which affected the protected natural area of the El Salado estuary and the beaches from Marina Vallarta to the Pitillal River.
“Work is underway on the construction of specific pieces that will be installed to reinforce the structure of the 48-inch tube,” the agency said.
The beaches are monitored every hour, after the problem so that there is no greater damage.
AND---You can really drink the water in Puerto Vallarta proper! One of the ONLY cities in Mexico deemed to have safe drinking water!!! (I think the other one might be Playa del Carmen but I'm not sure) However, I would probably still drink bottled water cause I'm just like that, but good to know!!!
Thanks to a dedicated effort at the local level, Puerto Vallarta is nearly peerless in its water quality when compared to other destinations in the country and around the world. The local government of Puerto Vallarta has invested millions into upgrading their water treatment facilities in recent years and holds the quality of its drinking supply to international standards. In fact, the city's municipal water supply, like that of all major cities nationwide, is evaluated at the processing plant for its quality on a yearly basis.
Not only has Puerto Vallarta's water been rated as perfectly safe for human consumption with a certificate of purity for 17 consecutive years, it is one of only two vacation destinations in the country to achieve this important distinction. Moreover, the city is well known for its attention to the quality of drinking water as a part of local culture, and major hotels and other accommodations often have their own dedicated filtration systems on top of the municipal filtration system.
And what about those beautiful beaches?
The Blue Flag accreditation means the beach is recognized as environmentally healthy per the strict standards of the Foundation for Environmental Education (FEE).
Mexico has a total of 53 Blue Flag beaches. Ten of them are located in the Puerto Vallarta area.
Water Quality is Paramount - The Blue Flag program requires that beaches achieve ‘excellent bathing water quality’ and must reach the water quality standard set by the Blue Flag program, or the standard set by their own municipality, whichever is higher.
The FEE is a nonprofit non-governmental organization that started in Europe but is now a worldwide organization. The Blue Flag is a trademark used by the FEE to indicate that beaches and marinas around the world are environmentally friendly, clean and safe
The biggest health issues I found were in regards to poor air quality and dengue fever.
Air quality - poor and pollen and from vehicle emissions for Puerto Vallarta.
Dengue Fever -
The municipalities with the highest number of confirmed cases of this disease are: Guadalajara with 351, Zapopan with 147, Puerto Vallarta with 103, Sayula with 77 and Autlán de Navarro with 66.
Dengue cases are on the rise and until the second week of August, there were 1, 204 reported cases and two deaths. Last year, until August 11, the Federal Ministry of Health registered no deaths by Dengue in the State of Jalisco, although PVDN cannot independently confirm those numbers.
The state agency recommends using repellent on skin and clothing, wearing long sleeves and pants for outdoor activities, placing mosquito nets on the windows and using household insecticides.
Also, to prevent mosquito reproduction, avoid leaving empty containers outdoors to prevent water from accumulating, keeping yards and gardens without weeds, cleaning trash and keeping household sinks chlorinated.