I went to the United States in 1994 for postdoctoral training in childhood lead poisoning research. My mentor, Dr John F. Rosen, a professor of pediatrics at Montefiore Medical Center's Albert Einstein College of Medicine in New York, was a leader in this field.

I had connected with him through professional activities and heard that the Rosen family had special affection for China.

But not until my arrival did I really feel their affection.

Helen Rosen, Dr John Rosen's mother, told me that her husband Samuel, her son John and grandson Carlo were all doctors.

When the Rosen family went to China, Chinese friends called all three of them "Dr Rosen," which confused them. They accepted friends' suggestion that the elder Rosen (grandfather Samuel) would be called "Old Rosen," his son John "Young Rosen," and his grandson Carlo "Little Rosen."

Old Rosen

Dr Samuel Rosen (1897-1981) was an internationally renowned otorhinolaryngologist (specialist in the ear, nose and throat). He invented a surgery known as Rosen's Operation that helped thousands of patients regain their hearing.

Old Rosen's China connection started in the 1930s, when Canadian physician Dr Norman Bethune (1890-1939) went to the front lines in China's War of Resistance against Japanese Aggression (1947-45) to aid Chinese troops.

Bethune had passed through New York and met Old Rosen. He urgently requested Rosen to raise funds, purchase medicine and medical equipment, and send them - via Madam Soong Ching Ling in Hong Kong - to the Chinese Army led by the Communist Party of China.

Dr Samuel Rosen and his wife Helen provided Bethune with essential medical supplies under extremely difficult conditions.

In 1965, then Premier Zhou Enlai personally wrote to the Rosens, inviting them to visit China.

Due to the lack of China-US diplomatic ties at the time, the couple arrived via Canada in 1971, on a trip carefully arranged by Huang Hua, then China's ambassador to Canada, and later China's foreign minister.

In Beijing they were warmly received by Premier Zhou and Madam Soong Ching Ling, with whom they had long corresponded but had never met. They were also introduced to Chinese colleagues in medicine.

With further normalization of relations, the elder Rosen couple led American medical groups on annual visits to China to lecture and train doctors and health practitioners.

They introduced state-of-the-art technology and information and donated equipment and computers to medical institutions.

Sadly, when Old Dr Rosen was leading a delegation in 1981, he died suddenly from a ruptured aortic aneurysm in Beijing Hospital.

According to his wishes, half of his ashes were scattered in China where he had devoted tremendous efforts, the other half returned to America.

Afterward, his widow donated all his savings and established the Samuel Rosen Foundation, which mainly supports Chinese doctors in US training and promotes medical exchanges.

To date, the foundation has fully or partially funded nearly 100 doctors studying in the US. Most have gone on to become key figures and academic leaders in their fields in China.

Young Rosen

In the Rosen family, Dr John F. Rosen (Young Rosen), was the person I knew best. He was already 60 years old when he trained me in childhood lead poisoning detection, prevention and treatment in the US. I was so sad to hear about his death and this story comes from my heart to show my respect for him.

Compared with his parents, he was quieter and more scholarly. But his actions told me his love of China was as deep as his father's.

In the US, renowned professors and doctors like Young Rosen are accustomed to being catered to. But his great concern for my well-being and comfort in the US surprised my American colleagues and touched my heart.

Prior to my arrival, he had rented an apartment for me in his name. To make me feel at home, he and his wife had carefully decorated my new place in Chinese style. All the decorations in the living room came from their home.

I still remember that when I arrived in New York, Young Rosen picked me up at the airport and drove me to his home. He asked me to promise him two things: First, he was my friend, John, and I must let him know whatever difficulties I encountered; second, I should regard his home as my own.

I benefited even more from his guidance and training at work. From my work plans to periodical summaries, he paid great attention to the smallest details. I was privileged to see him at any time, whereas my colleagues and visitors had to made appointments in advance.

No matter how busy he was, he would carefully review my work and painstakingly correct my English, word by word. I really learned a lot during the two-year training.

Like his parents, Young Rosen regarded improving child health in China as part of his career. In the late 1980s, he began collaboration with Shanghai Second Medical University (now the medical school of Shanghai Jiao Tong University) in research on childhood lead poisoning.

We found that with the rapid development of China's transportation industry, environmental lead pollution had become a serious problem affecting child health. However, the government failed to pay sufficient attention.

Young Rosen repeatedly wrote to the Ministry of Health to express his concerns and agreed to train professionals for China. Before I returned to China in 1996, he told me the Samuel Rosen Foundation would provide US$50,000 to support my Pediatricians Education Program, which aims to quickly train doctors to recognize childhood lead poisoning and provide clinical treatment.

After I returned to China, he visited Shanghai every year to guide our research, also sending medical equipment that we needed, which he paid for himself.

Dr Rosen also suggested a plan to send more young doctors to the US for training and research into childhood lead poisoning. All expenses would be paid. Under his plan, four of my students went to the US and all became outstanding specialists.

My biggest achievement with Dr John Rosen's help has been the great improvement in childhood lead poisoning control. We found that the prevalence of lead poisoning among Chinese children was higher than among children in western countries, and the major reason was vehicle exhaust from leaded gasoline.

The discovery prompted the State Council in 1997 to ban petrol containing lead. Following this, the childhood prevalence rate dropped from 38 percent to 3.87 percent.