Michigan Gov. Rick Snyder asked President Obama to declare both an emergency and an expedited major disaster in the county where the city of Flint has been dealing with the fallout from lead-contaminated drinking water. (Reuters)

The city of Flint, Mich., is in the midst of a water crisis several years in the making. The city opted out of Detroit's water supply and began drawing water from the Flint River in April 2014, part of a cost-saving move. Eighteen months later, in the fall of 2015, researchers discovered that the proportion of children with above-average lead levels in their blood had doubled.

The city reconnected to Detroit's water system in October, but the damage was done. Water from the Flint River was found to be highly corrosive to the lead pipes still used in some parts of the city. Even though Flint River water no longer flows through the city's pipes, it's unclear how long those pipes will continue to leach unsafe levels of lead into the tap water supply. Experts currently say the water is safe for bathing, but not drinking.

A group of Virginia Tech researchers who sampled the water in 271 Flint homes last summer found some contained lead levels high enough to meet the EPA's definition of "toxic waste."

The researchers posted their test results online, which I represent graphically below with other visuals to help understand just how high above normal Flint's lead levels really were.

Lead in water is measured in terms of parts per billion (ppb). If a test comes back with lead levels higher than 15 ppb, the EPA recommends that homeowners and municipalities take steps to reduce that level, like updating pipes and putting anti-corrosive elements in the water when appropriate.

But 15 ppb is a regulatory measure, not a public health one. Researchers stress that there is no 100 percent "safe" level of lead in drinking water, only acceptable levels. Even levels as low as 5 ppb can be a cause for concern, according to the group studying Flint's water.

So let's start with Flint's neighboring cities. At the city level, public health officials are most concerned with the 90th percentile level of lead exposure in homes they test -- that is, 90 percent of homes will have a lead level below this threshold, while 10 percent will register above it.

Forty-five minutes away from Flint in Troy, Mich., the 90th percentile level for lead in 2013 was 1.1 parts per billion. Not too shabby at all. In the graphics that follow, each splotch represents 1 part per billion. The splotches aren't proportionally scaled to the cups -- 1 part per billion is way too small to be visualized at this level. But all of the following graphics are scaled proportionally to each other, to give an impression of relative lead levels.


 

In Detroit, the water supply Flint had previously been connected to, the 90th percentile reading was 2.3 parts per billion -- still highly acceptable.


 

Here's an illustration of water at the 5 parts per billion level. This is below the borderline for EPA acceptability, but the team of researchers studying Flint's water say that levels this high can be a cause for concern, particularly for young children.


 

Now things get interesting. Here's a glass illustrating the 90th percentile reading among the 271 Flint homes tested by researchers last summer:


 

At 27 parts per billion, it's five times as high as the level of concern, and nearly twice as high as the EPA's already-generous guidelines. According to the researchers who ran these tests, the health effects of lead levels this high "can include high blood pressure and other cardiovascular problems, kidney damage and memory and neurological problems."

Recall, though, that 10 percent of the homes in the sample had lead levels even higher than this. Here's the highest lead reading in that sample, from a home in the city's 8th Ward:


 

That's more than 10 times the EPA limit. It's 30 times higher than the 5 ppb reading that can indicate unsafe lead amounts.

But that 158 ppb reading is far from the worst one that turned up in Flint, unfortunately. In the spring of 2015, city officials tested water in the home of LeeAnne Walters, a stay-at-home mother of four and a Navy wife. They got a reading of 397 ppb, an alarmingly high number.

But it was even worse than that. Virginia Tech's team went to Walters' house to verify those numbers later in the year. They were concerned that the city tested water in a way that was almost guaranteed to minimize lead readings: They flushed the water for several minutes before taking a sample, which often washes away a percentage of lead contaminants. They also made residents collect water at a very low flow rate, which they knew also tended to be associated with lower readings.

So the Virginia Tech researchers took 30 different readings at various flow levels. What they found shocked them: The lowest reading they obtained was around 200 ppb, already ridiculously high. But more than half of the readings came in at more than 1,000 ppb. Some came in above 5,000 -- the level at which EPA considers the water to be "toxic waste."

The highest reading registered at 13,000 ppb.


 

The professor who conducted the sampling, Dr. Marc Edwards, was in "disbelief."

"We had never seen such sustained high levels of lead in 25 years of work," he said.

According to Edwards, the team retested the water with extra quality controls and assurance checks, and obtained the exact same results.

You can check out their description of the testing at the website they set up for their water study. It includes unsettling photos of LeeAnne Walters' tap water containing rust and metal particles large enough to be seen with the naked eye.

The Walters family had stopped drinking the water a long time ago, according to the Virginia Tech team. But still, the lead levels were too high. One of Walters' 4-year-old sons was diagnosed with lead poisoning.

It appears that the city of Flint and state of Michigan have finally started to take the water problem seriously. Again, they reconnected the city to Detroit's supply back in October, but the water remains unsafe to drink.

In recent days the National Guard was activated to help distribute drinking water to the city's residents. And in yet another unsettling wrinkle in Flint's saga, 87 cases of Legionnaire's Disease, 10 fatal, have been diagnosed in the city since June. It's not yet clear whether that outbreak is linked to the water.