However, they show living closer to the incinerators themselves is associated with a very small increase in the risk of some birth defects, compared to the general population. But whether this is directly related to the incinerator or not remains unclear.

The findings come from the largest and most comprehensive analysis to date of the effects of municipal waste incinerators (MWIs) on public health in the UK.

MWIs are used to burn waste that is not recycled, composted or sent to landfill and can include materials such as paper, plastic, wood and metal. While MWI emissions are governed by EU regulations, public concern remains around their potential impact on public health and scientific studies to date have been inconsistent or inconclusive.

The analysis, led by a team at Imperial College London and funded by Public Health England and the Scottish Government, looked at MWIs at 22 sites across the UK between 2003 and 2010.

Researchers from the UK Small Area Health Statistics Unit (SAHSU) at Imperial first analysed concentrations of fine particles called PM10 (particulate matter measuring 10 micrometres or less in diameter) emitted from the chimneys of the incinerators as waste is burned.

Computer models generated from the data showed how these particles spread over a 10 km radius around 22 MWIs in England, Scotland and Wales. The models show that MWIs added very little to the existing background levels of PM10 at ground level – with existing PM10 concentrations at ground level on average 100 to 10,000 times higher than levels emitted by the chimneys (Environment Science & Technology, 2017).

Using these models, the team then investigated potential links between concentrations of PM10 emitted by MWIs and any increased risk of adverse birth outcomes. In an earlier study (Environment International, 2018), they found that analysis of records covering more than one million births in England, Scotland and Wales revealed no evidence of a link between small particles emitted by the incinerators and adverse birth outcomes such as effects on birthweight, premature birth, infant death, or stillbirth, for children born within 10 km of MWIs in Great Britain.

The team’s latest findings, published in the journal Environment International, looked at occurrence of birth defects within 10 km of a subset of 10 incinerators in England and Scotland between 2003 and 2010. In their analysis, the team used health data on more than 5000 cases of birth defects among over 200,000 births, still births and terminations in England and Scotland.

They found no association between birth defects and the modelled concentrations of PM10 emitted by MWIs, but there was a small increase in the risk of two birth defects among those living closer to MWIs – specifically congenital heart defects and hypospadias (affecting the male genitalia – where the opening of the urethra is not at the top of the penis). These birth defects typically require surgery but are rarely life-threatening.

In the UK, congenital heart defects affect approximately 5.3 in 1000 births and 1.9 per 1000 males are born with hypospadias (Source: NCARDRS 2016*).

In terms of excess risk, the team estimates that the associated increase in risk for these two birth defects could be around 0.6 cases per 1,000 total births for congenital heart defects and 0.6 cases per 1,000 male births for hypospadias within 10 km of an incinerator.

Professor Paul Elliott, Director of the UK Small Area Health Statistics Unit (SAHSU) said: “Based on the available data, our findings showing that there is no significant increased risk of infant death, stillbirth, preterm birth or effects on birthweight from municipal waste incinerators are reassuring. The findings on birth defects are inconclusive, but our study design means we cannot rule out that living closer to an incinerator in itself may slightly increase the risk of some specific defects – although the reasons for this are unclear.”

Professor Mireille Toledano, Chair in Perinatal and Paediatric Environmental Epidemiology at Imperial, said: “In these studies we found a small increase in risk for children living within 10 km of an MWI being born with a heart defect, or a genital anomaly affecting boys, but did not find an association with the very low levels of particulates emitted. This increase with proximity to an incinerator may not be related directly to emissions from the MWIs. It is important to consider other potential factors such as the increased pollution from industrial traffic in the areas around MWIs or the specific population mix that lives in those areas.”

Professor Anna Hansell, Director of the Centre for Environmental Health and Sustainability at the University of Leicester, who previously led the work while at Imperial College London, added: “Taken together, this large body of work reinforces the current advice from Public Health England – that while it’s not possible to rule out all impacts on public health, modern and well-regulated incinerators are likely to have a very small, or even undetectable, impact on people living nearby.”

The team explains that while the results of the emissions studies are reassuring, they cannot rule out a link between the increased incidence of the two birth defects and the activities of the MWIs. They add that while they adjusted their results for socioeconomic and ethnic status, these may still influence birth outcomes findings. Poorer families may be living closer to MWIs due to lower housing or living costs in industrial areas, and their exposure to industrial road traffic or other pollutants may be increased.

The researchers highlight that their findings are limited by a number of factors. Also, they did not have measurements (for the hundreds of thousands of individual births considered) of metals or chemical compounds such as polychlorinated biphenyls (PCBs) and dioxins, but used PM10 concentrations as a proxy for exposure to MWI emissions – as has been used in other incinerator studies.

They add that ongoing review of evidence is needed to explore links further, as well as ongoing surveillance of incinerators in the UK to monitor any potential long-term impacts on public health.

Traditionally, scientists have used light, x-rays, and electrons to peer inside tissues and cells. Today, scientists can trace thread-like fibers of nerves throughout the brain and even watch living mouse embryos conjure the beating cells of a rudimentary heart.

But there’s one thing these microscopes can’t see: what’s happening in cells at the genomic level.

Now, biophysicist Joshua Weinstein and colleagues have invented an unorthodox type of imaging dubbed “DNA microscopy” that can do just that. Instead of relying on light (or any kind of optics at all), the team uses DNA “bar codes” to help pinpoint molecules’ relative positions within a sample.

With DNA microscopy, scientists can build a picture of cells and simultaneously amass enormous amounts of genomic information, Weinstein says. “This gives us another layer of biology that we haven’t been able to see.”

Weinstein, Howard Hughes Medical Institute (HHMI) Investigator Aviv Regev, and molecular biologist Feng Zhang, who was selected as an HHMI investigator in 2018, report the work June 20, 2019, in the journal Cell.

“It’s an entirely new category of microscopy,” Regev says. “It’s not just a new technique, it’s a way of doing things that we haven’t ever considered doing before.”

Something new

Until now, microscopy fit into two main categories. The first is based on optics; light microscopy, for example, dates back to the 1600s and relies on visible light to illuminate samples. Scientists have riffed on this approach, even going beyond the visible spectrum. Electron microscopes, fluorescence microscopes, light-sheet microscopes ¬- they’re all based on the principle that samples emit photons or electrons, and the microscope detects the emission.

The second category is based on dissecting samples at locations defined by a microscope. Computer programs then stitch together each dissected piece into a complete picture of the intact sample. Optical imaging can offer intricate portraits of subcellular structure and action. Dissection-based microscopy can give scientists genetic information.

Weinstein and his colleagues at the Massachusetts Institute of Technology wanted to create a way to do it all in one shot — to take a snapshot of a cell’s position and spell out the specific genetic sequences driving it.

That combo is important for scientists studying genetically diverse sets of cells. The immune system is a perfect example, Weinstein says. Immune cell genes can vary down to a single letter of DNA. Each variation can trigger a dramatic shift in the type of antibodies a cell produces. Where that cell is located within a tissue can alter antibody production, too.

If you focus on just one or the other, “you’re only getting part of the picture,” he says.

How it works

Capturing such a complete picture of a cell doesn’t require an expensive microscope or a lot of fancy equipment, Regev says. All you need to get started is a specimen and a pipette.

First, scientists take cells grown in the lab and fix them into position in a reaction chamber. Then, they add an assortment of DNA bar codes. These stick to RNA molecules, giving each a unique tag. Next, the team uses a chemical reaction to make more and more copies of each tagged molecule — a growing pile that expands out from each molecule’s original location.

“Picture every single molecule as a radio tower broadcasting its own signal outward,” Weinstein says.

Eventually, the tagged molecules collide with other tagged molecules, forcing them to link together in pairs. Molecules located close to one another will be more likely to collide, generating more DNA pairs. Molecules further apart will generate fewer pairs.

A DNA-sequencing machine spells out the letters of every molecule within the sample, which takes up to 30 hours. An algorithm the team created then decodes the data — which, in the paper, represents roughly 50 million DNA letters of genetic sequences from each original specimen — and converts the raw data to images.

“You’re basically able to reconstruct exactly what you see under a light microscope,” Weinstein says.

The two methods are complementary, he adds. Light microscopy can see molecules well even when they’re sparse within a sample, and DNA microscopy excels when molecules are dense — even piled up on top of one another.

He thinks DNA microscopy could one day let scientists speed the development of immunotherapy treatments that help patients’ immune systems fight cancer. The method could potentially identify the immune cells best suited to target a particular cancer cell, he says.

Every cell has a unique makeup of DNA letters, or genotype, Zhang says. “By capturing information directly from the molecules being studied, DNA microscopy opens up a new way of connecting genotype to phenotype.”

The possibilities with this category of microscopy are wide open, Regev adds. “We hope that it sparks the imagination — that people will be inspired with great ideas that we’ve never thought about.”

“People with epilepsy have a high mortality rate, but it’s mysterious,” says Dan Mulkey, a neuroscientist in UConn’s physiology and neurobiology department.

More than one of every 1,000 people with epilepsy die each year from what’s called sudden unexpected death in epilepsy (SUDEP). No one knows why.

The explanation usually given is that the patient had a seizure that killed them. But seizures happen in the cortex, the top of the brain, and life-sustaining processes like breathing are controlled somewhere else entirely: the brainstem, the very bottom part of the brain that connects to the spinal cord. The two parts of the brain are quite distant from each other.

“It’s like, if the seizure is in New York, the brainstem is in San Francisco,” Mulkey says.

Many neurologists argue that a particularly bad seizure can travel down through the brain from the cortex to the brainstem to cause breathing or heartbeat malfunction, and that’s what kills in SUDEP. But Mulkey doesn’t buy it. People die of SUDEP without having an obvious seizure, and epilepsy patients can have breathing problems in the absence of seizures.

Instead, Mulkey and his colleagues, graduate students Fu-Shan Kuo and Colin Clearly, wondered if there was a genetic basis for SUDEP. Perhaps the same genetic mutation that causes the seizures also disrupts the cells in the brainstem that control breathing.

Kuo raised mice with the human mutation for a severe form of epilepsy called Dravet syndrome. Dravet syndrome is caused by mutations in a gene that shapes the channels through which sodium moves in and out of cells in the brain. If the sodium channels don’t function properly, cells can get overexcited. One cell’s overexcitement can travel through the brain like hysteria through a crowded stadium, stampeding into a seizure.

The gene mutated in Dravet syndrome is called sodium channel gene 1a, or Scn1a. It’s considered a super-culprit for epilepsy, with more than 1,200 different Scn1a mutations identified. The severity of the epilepsy caused by Scn1a depends on whether the mutation causes partial or complete loss of the sodium channel’s function. The Dravet mutation is on the severe end of the spectrum. People with Dravet syndrome tend to have dramatic seizures, exacerbated by hot weather, and the syndrome is very hard to control with anti-epileptic medications. SUDEP is sadly a frequent way for people with Dravet syndrome to die.

There’s a somewhat paradoxical part of Dravet syndrome, too: this Scn1a mutation makes the sodium channels less active, not more. Instead of making cells overactive, it makes them underactive. But there’s a catch. This mutation mostly affects inhibitory cells — that is, cells in charge of calming the brain down. They’re the stadium bouncers, so to speak. And if the bouncers are asleep on the job, the overexcited neurons can stampede uninhibited.

To understand how this might lead to SUDEP, Kuo wanted to test two things: first, whether the mice with the Dravet syndrome mutation show breathing problems and die prematurely of SUDEP, and second, whether the cells in the part of the mice’s brainstem that controls breathing were normal or were somehow perturbed by the mutation.

The first question was answered quickly: the mice with Dravet syndrome had bad seizures that became more severe when the mice got hot, exactly like humans with Dravet syndrome. They tended to die very young, in a manner similar to SUDEP; none lived much past three weeks.

The second question took longer to answer, but there were early clues that Kuo and Mulkey were on to something. The mice with Dravet Syndrome had disordered breathing. They tended to hypoventilate (breathe too little) for no apparent reason sometimes. Other times they would have long apneas, or pauses between breaths. And these mice didn’t breathe more in response to high carbon dioxide levels in the air, the way humans and normal mice do.

“We felt really good that our model was reflecting the human condition,” Mulkey says.

The next step was to actually look at the mice’s brainstems and see if something was wrong.

When Kuo zoomed in on the part of the brainstem that controls breathing, she saw that the inhibitory cells — the stadium bouncers of the brainstem — were definitely less active than they should have been. This led the excitatory neurons to run wild, and constantly tell the part of the brain that generates the breathing rhythm to push faster. But shouldn’t this lead to increased breathing, not stopping?

There is definitely something wrong with the breathing circuit in the brainstem in these mice, but Mulkey and Kuo cannot pinpoint the exact problem. So they’re still on the case. The next steps will be to look at mice that only express the Scn1a mutation in the brainstem or only in the cortex, and see if they also have problems. If mice with a mutation in the cortex but not the brainstem don’t have SUDEP, that would argue against the ‘seizure descending from cortex to brainstem’ hypothesis. The researchers also plan on looking at other parts of the breathing circuit to see whether other parts have gone haywire, too. Eventually, they hope to identify a key player that can be calmed — or prodded — to prevent the breathing system from breaking down, and ultimately save the lives of people with epilepsy.