YONG'AN VILLAGE, China – At the height of the corn harvest in the long muggy days of August, 10-month-old Zhang Peng began refusing to drink his milk, crying fitfully at night as he struggled to sleep. Soon his twin sister Zhang Xue fell ill, too.
Several times, their parents brought the sick babies, who had trouble urinating, to the nearest hospital 20 miles from their farming village. Doctors could not diagnose the problem but gave the children herbal powder and injections.
Then last month, Chinese media revealed that infant formula contaminated with melamine, an industrial chemical used to make fertilizer and plastics, was sickening babies nationwide.
The news shocked the Zhang family and so began a monthlong ordeal that would see them shuttling back and forth between their home in Shandong province and a hospital in Beijing, 450 miles away.
"We had no idea what was wrong. We were so frightened and worried," the children's mother, Liao Shanfang, told The Associated Press this week from the family's simple house in this village in eastern China's corn belt.
"Even when I saw the news that milk powder had been poisoned, I could not believe it. We never imagined that would be the problem."
Amid China's worst food-safety crisis in years, thousands of parents have jammed into hospital emergency rooms. More than 50,000 children have been treated for kidney ailments and nearly 6,000 remain hospitalized, the Health Ministry said this week. Four deaths have been linked to the toxic milk.
Experts say the long-term effects of prolonged exposure to high levels of melamine have not been studied in humans, but infants and young children are most vulnerable.
"They start off with the simplest immune system, the nervous system still developing," said Peter Dingle, a toxicity expert at Murdoch University in Australia. "They don't have the biochemistry in their body to break down the chemical and eliminate it the way adults do."
After the tainted milk scandal broke in mid-September, Liao and her husband Zhang Rongwei took their twins yet again to their local hospital in Linyi.
This time, Zhang Peng, the boy, was admitted for a five-day stay but he only got worse. He began vomiting and when he could urinate, it came out in a thin, blood-tinged stream. His sister's symptoms weren't as serious; she had sporadic fevers.
From birth, both babies had been given breast milk and formula. The Zhangs first used a cheaper brand that gave the children diarrhea, then switched to one made by Sanlu Group Co., although it cost almost twice as much.
Sanlu was the first company implicated in the scandal, going public with word of contamination on Sept. 11, and the Chinese government later confirmed it was widespread. Unscrupulous suppliers are suspected of adding melamine to watered-down milk to make it appear protein-rich in quality tests.
"These people working at the milk powder companies have no conscience and only care about making money," Liao said angrily. "I'm just disappointed because the government should have done more to protect its citizens."
Plump and round-headed, the Zhang twins had been healthy and affectionate at first. Zhang Xue loved to gnaw on her fingers and smile, showing off her baby teeth. Zhang Peng was more serious but always curious. By September, both babies were listless.
Unable to do more to help them, doctors in Linyi told the Zhangs to seek treatment in Beijing.
The couple hastily arranged for a car ride — at a cost of 300 yuan, about $45, a small fortune — to the Children's Hospital in the capital, where they arrived Sept. 23.
Hours later, Zhang Peng was diagnosed with two large kidney stones that needed surgery. His sister had a single stone the size of a grain of rice — not serious enough to warrant a hospital stay.
"My heart stopped when I read the test results for Zhang Peng," Liao said.
With no choice but to split their lives — and their children — the couple brought their daughter home to her paternal grandmother. Then they returned to Beijing where they spent the next three weeks, sleeping at a relative's home an hour-long bus ride from the hospital.
While hospital treatment was free under a central government mandate, the trip to Beijing was not without significant cost. The burden of harvesting the family's corn fell to Zhang's parents. Travel between their village and Beijing took 10 hours each way.
In a good year, the couple's income is about $1,300. Liao estimated that while they were in Beijing, the family spent about $1,000 and with Zhang unable to work, their losses mounted further.
Ever since the twins were born, the couple, who also have an 11-year-old daughter, have worried how they would support their larger-than-expected family. As rural Chinese, they were permitted by China's strict one-child policy to try for a second child. They ended up with twins.
To make ends meet, the couple worked their fields, while Zhang, a slight 31-year-old, also took odd jobs — repairing floorboards, construction work, ferrying passengers in his motorcycle cab. Child care was split with Zhang's parents, who took in the baby boy when he was 7 months old. Liao, 32, cared for the baby girl and their older daughter.
Despite the weeks of heartache, the twins, who turn 1 this month, are now on the road to recovery. Zhang Peng was discharged from the hospital Monday; his sister was treated with a remedy prescribed by a traditional Chinese medicine doctor.
The toddlers still drink milk but only brands unaffected by the scandal — Red Star, made in China's northeast, and the U.S.-based Wyeth Nutrition. They cost nearly five times what Sanlu milk cost.
"When we bought them, we were told these had passed quality tests," Liao said as her husband measured out milk powder. "We still feed them milk because without milk, she would be crying."
Zhang Xue hungrily gulped a bottle before settling down to play with a ball on the concrete floor of the family's home, where bright yellow summer corn lay drying in the front yard.
Her brother, brought over from his grandparent's house for a visit, leaned toward her. They smiled as their foreheads touched.
Associated Press writers Chi-Chi Zhang and Xi Yue in Beijing and Robin McDowell in Jakarta, Indonesia, contributed to this report.