Pollution characteristics and health risk assessment of arsenic transformed from feed additive organoarsenicals around chicken farms on the North China Plain

Highlights

• Arsenic is widely present in chicken feed, manure, and surface soil with different species.

• Arsenic accumulated in chicken manure and surface soils.

• A typical pollution pattern of arsenic was developed to clarify the pollution process from feed to soil.

Abstract

Arsenic is frequently found in poultry waste, most of which is transformed from feed additive organoarsenicals, resulting in arsenic pollution of soils and water around poultry farms. The North China Plain, an important area for livestock breeding of China, was chosen to investigate the pollution characteristics and assess the health risk of arsenic around chicken farms. Among the 138 chicken farms sampled, almost no roxarsone, a common organoarsenical, was detected in chicken feeds, manure, and surface soils, while the detectable rate of other arsenic species was high. Because of long-term enrichment, the concentrations of arsenic species in manure were generally higher than that in feed. As(III) was the main inorganic arsenic species in the manure, where is reducing environment. In surface soils beneath the accumulated manure, As(V) was the predominant arsenic species with 100% detectable rate. The detectable rate and average concentrations at 0 cm were generally higher than those at 25 cm depth, indicating that arsenic accumulated in the surface soils. In addition, a typical conceptual diagram of arsenic was developed to clarify the pollution process from feed to soil. Through health risk assessment of inorganic arsenic, the carcinogenic risk (CR) and non-carcinogenic risk (non-CR) were both negligible. The city of Jiaozuo had the highest CR and non-CR, which was 11 times higher than that of the city with the lowest risks. This study presents a clear picture and evaluation of arsenic pollution on chicken farms, inspiring future studies assessing arsenic pollution after the ban of organoarsenicals.

Introduction

Arsenic (As) is generally recognized as a toxicant and carcinogen that can cause serious disturbances of the cardiovascular and central nervous systems (Joseph et al., 2015). As is frequently found in poultry waste, which is often disposed of in open stockpiles or through farm land application, without appropriate leachate control or formal treatment. This can result in As contamination by poultry manure through precipitation and leaching into the surface soil, vadose zone, and groundwater. The poultry industry has been developing rapidly in China, accounting for an increasing proportion of the agricultural economy. The production of broiler chickens increased from 2 × 10³ million in 1985 to 1 × 10⁴ million in 2010 (Wei, 2014). The rapid development of poultry production has exacerbated As pollution from poultry manure.

As in poultry manure mainly comes from feed containing organoarsenicals. Organoarsenicals are low toxicity compounds that are used worldwide as feed additives to promote livestock growth, enhance meat pigmentation, and fight intestinal parasites (Kowalski and Reid, 1975; Lindsey and Konkel, 2016; Mangalgiri et al., 2015). There are many kinds of organoarsenicals, including roxarsone (ROX), p-arsanilic acid (ASA), carbarsone, and nitarsone, among which ROX is most common in chicken feed. Although most ROX is excreted unchanged to the environment through poultry urine and manure (Morrison and Louis, 1969), chickens fed with ROX had increased levels of inorganic arsenic (i-As) in livers and muscles when compared with blank controls (Lasky et al., 2004; Nachman et al., 2017). After ROX enters the environment, it is easily degraded into i-As, dimethylarsinate (DMA), monomethylarsonate (MMA), 3-amino-4-hydroxarsoneyphenylarsonic acid (HAPA), and other As species through biotic and abiotic action (Cortinas et al., 2006; Huang et al., 2019; Liu et al., 2017b, 2017c; Meng et al., 2019; Yang et al., 2016). Because of human and environmental health concerns, the European Union and the United States of America banned the use of ROX in 1999 (European Commission, 1999) and 2013 (U.S. Food and Drug Administration, 2013), respectively. In China, ROX and ASA were permitted to be used until May 1, 2019 (Ministry of Agriculture of the People’s Republic of China, 2018). However, ROX, which is stable and undergoes limited migration, has been used for decades, which has resulted in the accumulation of large amounts of As in the environment. Our previous study found that the As concentration in the compost site of a chicken farm in Liaocheng, China was significantly higher than that in the background soil (Liu et al., 2017a). The workers in chicken farms are likely exposed to As pollution through contact with ROX or i-As distributed in air, dusts, waste, and water. Because the toxicity of As is species dependent, describing the exact distribution of As species is important to evaluate their environmental impact.

The North China Plain is an important area for livestock breeding in China, and groundwater is an important water resource for daily life in this region. The As pollution from poultry farms could have great impact on residents in this region. The purpose of this study was to: (1) investigate the As pollution of chicken farm wastes in the North China Plain; (2) determine the different As species and concentrations in feed, manure, soils, and groundwater around the chicken farms; and (3) assess the health risk of i-As pollution in terms of heavy metal accumulation in soil. Because this study was carried out before organoarsenicals were banned, it provides a baseline that could be used as a comparison for future studies after the ban of organoarsenicals.