This week, the overall grades of 3 Chemicals stocks are lower, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

LyondellBasell Industries NV (LYB) slips from a C to a D this week. LyondellBasell Industries NV produces chemicals, fuels, and polymers used for packaging, clean fuels, durable textiles, medical applications, construction materials, and automotive parts. The company also gets F’s in sales growth. For more information, get Portfolio Grader’s complete analysis of LYB stock.

Syngenta AG Sponsored ADR (SYT) declines this week from a C to a D. Syngenta AG Sponsored ADR is an agribusiness that is engaged in the discovery, development, manufacture and marketing products designed to improve crop yields and food quality. The company also gets F’s in sales growth. For more information, get Portfolio Grader’s complete analysis of SYT stock.

Calgon Carbon Corporation’s (CCC) rating weakens this week, dropping to a F versus last week’s D. Calgon Carbon Corporation is engaged in products and services for purifying water and air. The company also gets F’s in sales growth, earnings revisions, and earnings surprise. For more information, get Portfolio Grader’s complete analysis of CCC stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.