If you are a new mother and unable to breastfeed, few places are better than Brazil when it comes to getting assistance. Milk banks, which collect donated breast milk and distribute it to mothers and babies in need, have existed since the early 20th century, but they were frequently expensive and not widely accessible. But in the 1980s, Jo茫o Apr铆gio Guerra de Almeida, a young chemist, worked with Brazilian public health officials to redesign the country鈥檚 milk banks from the ground up, using cheap, creative solutions like repurposing hot water baths from the food industry that were 10 times cheaper than standard pasteurisation machines, or sterilising coffee and mayonnaise jars so they could be reused as milk bottles.

The Brazilian word for this imaginative problem-solving is jeitinho, says photographer , who, with the journalist Niklas Franzen, visited and reported on several of Brazil鈥檚 milk banks, like the Fernandes Figueira Institute in Rio de Janeiro.

Today, Brazil鈥檚 milk-bank system is frequently cited as one of the world鈥檚 best, providing some of the world鈥檚 cheapest and safest breast milk. It operates at a vast scale, with more than 200 milk banks 鈥� the most in the world 鈥� serving hundreds of thousands of babies. Brazil saw a more than 70 per cent drop in mortality of children under 5 from 1990 to 2015, which credited at least in part to its milk bank system.

On top of its efficiency, part of the reason for the system鈥檚 success is that it makes it easy for women to freely donate and receive milk, supported by a network of courier drivers who crisscross the country. One of these drivers can be seen delivering milk by bike in Flamengo, a suburb of Rio de Janeiro (above). 鈥淲e spoke to one donor, and she said, if it wasn鈥檛 for a courier to pick up her milk, she wouldn鈥檛 do it, it would just not be possible,鈥� says Bethge. 鈥淭his would be really nice for Europe and for other countries鈥�, to adopt, she adds.

The milk banks themselves are also multipurpose facilities, acting as holistic support centres for new mothers, collecting milk, sterilising and storing it, as well as supplying it directly to premature babies in need. All milk is first checked for large contaminating detritus, such as hair or dust, that would result in a sample being rejected (above). The milk is then warmed up and liquefied in a water bath (below), so that it can undergo more rigorous tests to ensure that it is free of biological contaminants (main image, top).

Women can also receive assistance from nurses to help express milk for their babies if they are in need, such as in wards for premature births (below).

鈥淵ou see the whole circle, from the woman who was delivering [the milk] to the baby who gets it,鈥� says Bethge.

With Europe in the grip of a mega heatwave and deaths already being reported, staying cool isn鈥檛 just about comfort 鈥� for many, it is a matter of life and death. Many people will be relying on fans rather than air conditioning, so it is important to be aware that, as it gets hotter, fans can flip from cooling you to warming you.

But how hot is too hot? The UK government warns , whereas the World Health Organization says . Some studies suggest even lower or . The reality is that there is no simple answer, as several factors are involved.

The key thing to know is that you become less good at sweating as you age, so fans will start to warm you at a lower temperature than is the case for younger people. However, you can compensate for this by spraying yourself with water or wetting your clothes.

The situation would be very simple if we didn鈥檛 sweat. Our skin temperature in the shade is typically between 35掳C and 37掳C (99掳F). If the air temperature is lower than our skin temperature, heat is transferred to the air, cooling us, but if it is higher, we gain heat from the air. Moving air over our skin with a fan speeds up this heat transfer, whichever way it is going.

Because of this, in the past, 35掳C was often said to be the point at which fans stop cooling us, says in the UK. But this number doesn鈥檛 take account of evaporative cooling.

The evaporation of water transfers lots of heat from our skin into the air, cooling us even when air temperatures exceed skin temperatures. But blowing air over our skin with a fan doesn鈥檛 necessarily cool us more if it鈥檚 too dry or too humid.

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When it is very dry, our sweat can evaporate as fast as we produce it. In this situation, turning on a fan won鈥檛 help, because evaporation cannot increase any further. Instead, the moving air will just transfer more heat to your skin. For instance, modelling and experiments show that at 15 per cent humidity and 45掳C, turning on a fan will almost certainly .

But as the humidity rises, evaporation slows because there鈥檚 already lots of moisture in the air. Basically, if you are dripping with sweat, you are producing sweat faster than it can evaporate. In these conditions, a fan does help.

For instance, a fan can still cool you at up to 60 per cent humidity and 38掳C. As the humidity gets even higher, however, evaporation will slow to a point when a fan stops helping.

鈥淪o it depends on the humidity in the air,鈥� says Havenith. 鈥淭hat鈥檚 why people often look at what kind of climate you have in different countries.鈥�

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The other big factor is age. As we age, our body temperature and skin temperature can fall. It also takes longer for us to start to sweat, and we produce less sweat. This means the temperature at which a fan will start warming us at a given humidity declines as we age.

In this situation, wearing wet clothes or spraying ourselves with water can help. This can also reduce sweating and thus reduce the risk of dehydration.

Many other factors also play a part, such as clothing and whether your body is adapted to high temperatures. The bottom line, however, is that if you live in a building that gets really hot, temperatures during this heatwave could well exceed the level at which fans will help, even if you鈥檙e spraying yourself with water.

鈥淎t that stage, you probably would have to leave your house and find a cooler place,鈥� says Havenith. 鈥淏ecause it鈥檚 a really bad situation.鈥�