Summertime（夏季） is vacation time. Here in Germany most car owners still prefer to drive, even to distant holiday destinations. When it comes to road safety, tires are of course of paramount（极为重要的） importance. More than 50 million are sold each year in Germany alone. It's a multi-billion dollar business. But where do these tires come from?

  And under what conditions are they produced? The tires of my family car are well past their prime. They're getting old and are a bit brittle. The need to replace them ahead of a family vacation has got me thinking about the origin and sustainability of tires on the market. Reifen Steebling, a family-run business, is one of the biggest independent dealers in western Germany. I'd like to buy a set of new summer tires and want some advice.

  The store stocks, the standard brands, they're all good quality. But I have a different question on my mind. Can I tell where a tire was produced? Is that possible? Made in China（瓷器） and Japan, the Czech Republic（共和国）, tires are clearly produced all around the world. Are customers interested under what conditions the tires are produced?

  Very few, to be honest. The customers aren't interested in sustainability. How the tires are produced. For us it is of course an important factor. But very few customers are interested, to be honest. But the sales advisor is convinced that his products meet sustainability standards.

  So I could buy any of these with a clear conscience（良心）. Big name manufacturers place a lot of importance on sustainability. So I think it would be better to stick with them, because you can be sure that they are aware of environmental issues. And so I think you can buy tires with a clear conscience. We want to make our own assessment. So we head off for Southeast Asia.

  Thailand（泰国） is the world's biggest producer of natural rubber. More than 4 million tons of it are harvested（收割） on its plantations each year. Over the last 30 years, production here has grown by 300 percent. Bangkok is the center of the rubber trade. We're meeting journalist V. Intra Khatuk, who's written extensively about the industry.

  Even from the car, it's clear what a big role the tire industry plays in Thailand. After all, it's not just natural rubber that is produced here, but many tires are too. They're then shipped around the world in containers. But it's not easy to get a glimpse（一瞥） inside the business here. Well, as the rubber industries play the important role to Thai（泰国（人的）） economy, I think the people in this industry might want to keep some secret with them. So it's quite a bit difficult to get information from them.

  Our first stop is in Kao Kamau District, southeast（来自东南） of Bangkok. Large amounts of rubber are grown here. Thanks to V's contacts, we gain access to one of the plantations. The owner inherited the plantation from his parents. In the past, this area was rainforest. My parents cleared the whole area and started cultivating（培养） it.

  First, they planted rice and sugar cane, but later they switched to rubber. The plantation begins right behind his house. For the first time, we see how rubber is harvested. The rubber latex drips out of an incision（切割） in the bark of a tree. It can be harvested in a liquid state, or through the addition of vinegar, as they're doing here, to get the rubber to solidify（ 巩固） and harvest（收割） it in solid pieces. Bao Supat employs more than 50 workers on his plantation.

  Later, we will discover what kind of conditions they live in. Bao Supat has just planted new rubber trees, despite a glut on the market that's driven a steady drop in the price per kilo. We used to earn good money with our rubber. But five years ago, the price suddenly plummeted（垂直落下）. Now we have to save where we can to get by. If the plantation owner himself is feeling the pinch, what about his workers?

  On the edge of the plantation, we find their decrepit（衰老的） huts. The workers all come from neighboring（友好） Cambodia. They're willing to work（使工作） for lower wages than ties. I work 12 hours a day, five days a week. Sometimes more. Night has fallen on Bao Supat's plantation.

  It's the best time to harvest rubber. The Cambodians are getting ready to go to work. Their night shift starts at 8 p.m. and ends at about 5 in the morning. With just head torches for light, they slice deeper and deeper grooves（(唱片等的) 凹槽） into the tree trunks to keep the milky（乳白色的） latex flowing. Night has been working on the plantation with her family for the past seven years.

  The 23-year-old can't read or write. I earn very little here, between 4,000 and 5,000 baht a month. For that, I have to work every day and at least four nights. Hard night shifts for a mere（仅仅） 140 euros a month. That's around half of the minimum wage in Thailand, which is itself hardly generous. The family always gathers at 5 in the morning to eat, but sometimes they have to go without.

  In the rainy season, we can't work and don't get paid. Then we often don't have anything to eat and have to go hungry. When it gets light, Na's daughter heads off to school. She only gets to see her mother briefly. The rest of the family is going to bed. They own just two mattresses, shared between eight family members.

  Outside is Na's brother. His job today? Spraying herbicide（[农药] 除草剂）. He's using the extremely toxic（有毒的） product Paraquat, long outlawed（宣布…为不合法） in Europe. Da feels safe wearing a mask（面具）. What the 25-year-old doesn't realize is that Paraquat can also be absorbed through the skin and can lead to severe kidney（[解剖] 肾脏）, liver（肝） and heart damage.

  He should by no means be working without protective（保护的） clothing in shorts. But no one has told him that. Before the harvest, we have to kill the grass with poisonous chemicals. Otherwise, snakes could hide in the grass between the trees and bite us. This is what it looks like before the herbicide is used, and this is what it looks like afterwards.