The Excretion Of Manure-borne Steroid Estrogens In China And The Estimation Of Their Potential Ecological Risk

As a kind of vertebrate metabolites, natural steroid estrogens, which contain estrone,17α-estradiol,17β-estradiol and estriol, may entry into environment through the human andanimal solid manure and urine. Steroid estrogens have been implicated as environmentalendocrine disrupters because exposure to these chemicals, even at levels as low asnanograms-per-liter (ng/L), can adversely affect reproduction in a wide variety of wild species.In China, the emission of manure-borne estrogens and its ecological risk have not beenstudied yet, despite the fact that strong links between animal farming and environmentalcontamination with estrogens have been proven in international literatures.An estimated method was developed in this study to predict the manure-borne estrogenicemission of animal agriculture in China, and the potential risk of estrogens to the cultivatedland and surface water was assessed then. Firstly, the emissions of manure-borne steroidestrogens in provinces of China were estimated. After chosen as the typical districts of animalfarming, the estrogenic excretions of the Three Northeast Provinces, the eleven provinces andmunicipalities in the Yangtze River basin, as well as the municipality of Beijing wereanalysed particularly. Secondly, the manure-borne estrogenic concentrations in the cultivatedland and surface water were predicted in these typical areas of animal farming. Finally, theestimated excretions of dairy and beef cattle were examined by the previous determination ofsteroid estrogens in cattle manure. At the same time, the predicted manure-borne estrogenicconcentrations in surface water were proved to be reasonable by former literatures.The total manure-borne estrogenic emission of swine was the largest in the five typicallivestock and reached30591.8kg till2008. The laying hens had the fastest growth rate, whoseestrogenic excretion in2008was9times greater than ten years ago. In the typical areas ofanimal farming, Sichuan province had the greatest annual emission, which reached5114.0kgin2008. The growth rate was the fastest in Jilin province, whose increment reached1607.1kg,and the excretion in2008was more than twice of1998. Meanwhile, the emission ofmanure-borne estrone was the greatest contributor to the total amount of estrogens. The swineurine, poultry feces and cattle urine had the largest contribution rates to the excretions ofestrone,17β-estradiol and17α-estradiol, separately.While the emission of estrongens was estimated, the manure-borne estrogenicconcentrations in cultivated land and surface water were predicted in Liaoning, Jilin, Heilongjiang, Sichuan, Hunan, Jiangsu, Beijing, Chongqing and Shanghai, because of theirgreat excretions. The estrongenic load of cultivated land in Beijing was the highest in studyareas, as well as the predicted concentration of17-estradiol equivalent in the surface water,reached839.1mg/hm2and23.3ng/L, respectively. The fastest growth rates of these two itemswere both in Liaoning province, whose increments reached291.9mg/hm2and9.3ng/L from1998to2008, separately. The predictions indicated that the pollution risk of manure-borneestrogens to the cultivated land was greater in north areas of China, as well as the risk to thesurface water. Specially, the excretions of manure-borne estrogenic contaminants in Beijingand Liaoning should be controlled more strictly in study areas because of their largeemission and obvious increase.For the purpose of examining the estimated emissions of manure-borne estrogens, theprevious determination of steroid estrogens in dairy and beef cattle manure was comparedwith the predicted excretions of dairy and beef cattle in this study. The result showed that theestimated excretions of dairy and beef cattle in this study were both lower than the previousdetermination, but the differences were not obvious and the predictions were reliable.Therefore, the estrogenic excretions of dairy and beef cattle in study areas could be reflectedby the estimations in this study. At the same time, the predicted concentrations of17-estradiol equivalent in the surface water in Beijing, Liaoning and Jiangsu, whosepredictions were23.3,17.1and12.7ng/L, respectively, were similar to the previous reports.In summary, the predicted excretions of dairy and beef cattle in this study, as well as theestrogenic concentrations in surface water, were reasonable, scientific and reliable.